WO2019175341A1

WO2019175341A1 - "a stent, and a method for the treatment of an aneurysm in an intracranial vessel"

Info

Publication number: WO2019175341A1
Application number: PCT/EP2019/056472
Authority: WO
Inventors: Sven Tommy ANDERSSON
Original assignee: Ceroflo Limited
Priority date: 2018-03-14
Filing date: 2019-03-14
Publication date: 2019-09-19
Also published as: GB201804070D0

Abstract

A stent for use in a method for the treatment of an aneurysm (3) in an intracranial vessel (5) comprises an expandable framework (7) and a film (22) formed thereon by spraying, sputtering, dipping or the like of a polymer material. The stent comprises a central bridging portion (25) for bridging and closing the aneurysm (3) and first and second non-bridging portions (26) and (27). First communicating openings (29a) extend through the film (22) in the central bridging portion (25) and communicate with a central diverting bore (17) extending longitudinally through the framework (7) for accommodating blood flow therethrough to the aneurysm (3). Second communicating openings (29b) extending through the first and second non-bridging portions (26) and (27) accommodate blood flow from the diverting bore (17) to side vessels (30) and perforators (31 ) extending from the vessel (5) at respective opposite ends of the aneurysm (3). The area of the first communicating openings (29a) is less than the area of the second communicating openings (29b). The spacing between the first communicating openings (29a) is greater than the spacing between the second communicating openings (29b) so that blood flow is considerably restricted to the aneurysm (3), while normal blood flow is maintained to the side branches (30) and perforators (31).

Description

“A stent, and a method for the treatment of an aneurysm in an intracranial vessel”

The present invention relates to a stent, and in particular, to a stent for use in the treatment or alleviation of an aneurysm or a vessel wall deformity in an intracranial blood vessel. The invention is also directed towards a method for the treatment of an aneurysm or a vessel deformity in an intracranial blood vessel. Additionally, the invention is directed towards use of the stent in the treatment of an aneurysm or a vessel deformity in an intracranial vessel.

Stroke can be broadly classified into two major subtypes: ischemic and haemorrhagic. About 87% of strokes are ischemic while the remaining are haemorrhagic. A haemorrhagic stroke is the result of a ruptured blood vessel, usually due to abnormalities in vascular structures such as intracranial aneurysms, arteriovenous malformations and so on.

Cerebral aneurysms are pathological focal dilatations of the arterial wall that are often found at and around the junctions of the circle of Willis. Their weak walls predispose aneurysms to rupture resulting in a haemorrhagic stroke, called a sub-arachnoid haemorrhage, which carries a high morbidity and mortality rate. Endovascular treatment has become the first-line treatment in the management of both ruptured and unruptured aneurysms. Advancements in neurointerventional procedures have meant that interventional treatment strategies such as intracranial stenting and coil embolization, with or without stent assistance, have become feasible. Early developments focussed on filling the aneurysm with coils. Stents, however, have become one of the most important tools in treating difficult aneurysms, not feasible for simple coiling.

T raditional neurovascular stents come in a variety of different forms, for example balloon-expanded stents which are in most cases made of steel suitable for medical purposes and transported by means of a balloon catheter to the placement site where they are expanded hydraulically. Alternatively, there are stents made of a self-expanding material such as a nitinol (nickel-titanium alloy) and advanced in a collapsed or contracted form by means of a catheter to the placement site, where they are deployed and expand to their unconstrained shape. These stents are self-expanding due to the design and the construction of the stent from shape memory alloys. Although there are a wide variety of stent forms available to a surgeon, the most commonly-selected type is a tubular stent which is formed as a cylinder and collapsed as tightly as possible to present a low profile to allow passage of the stent through small lumen catheters that are required for interventional neuroradiological procedures. The stents are deployed either through unsheathing or pushing the stent out of the catheter, or a combination of both techniques. Conventional stent construction comes in a variety of different designs that are referred to as open cell or closed cell, with each stent type having variable properties. The Neuroform stent (Neuroform is a registered trade mark (RTM) of Stryker Corporation) has an open cell stent design, while closed cell designs include the Enterprise stent (RTM of Codman Neuro). Other design features are included in some stent designs. For example, a longitudinal slit is provided in the Solitaire stent (RTM of Medtronic pic). Open cell and closed cell stents are generally formed through a laser cutting a tube.

Shape-memory alloy, such as a nitinol, can transform from a Martensitic phase to an Austenitic phase through a change in temperature. The exact temperature at which this occurs is dependent on the composition of the alloy and neurovascular stents typically undergo this change at or close to body temperature. These types of expandable stent exhibit sufficient force and rigidity that they remain expanded after the catheter is removed. Below its transition temperature, the stent is in its Martensitic phase which is much more deformable so that the stent can be compressed into a smaller profile to fit better into smaller microcatheters ready for deployment. Above its transition temperature, the stent moves into its Austenitic phase and reverts to its original shape and thereby expands to fit a blood vessel. Above its transition temperature, nitinol is super-elastic with good outward radial force. The stent therefore needs to be held in its collapsed, compressed state by means of a retaining mechanism during delivery of the stent.

Stents can be designed to be retrievable or irretrievable. Retrievable stents can be positioned into the body and placed temporarily to assist with procedures and then removed when no longer required. Irretrievable stents are not routinely removable from the body once deployed in the vascular system.

More recent developments in treatment of cerebral aneurysms have focussed on parent vessel reconstruction using flow diversion.

Flow diversion is an endovascular technique whereby instead of placing a device inside the aneurysm sac, such as with coiling and traditional tubular stenting, a device is placed in the parent blood vessel to divert blood flow away from the aneurysm itself. A flow diversion procedure may be performed to treat an unruptured brain aneurysm. By employing a flow diversion technique, rather than a strategy such as coil embolization, the surgeon does not need to enter the aneurysm itself, thereby greatly reducing the risk of rupturing the aneurysm during surgery. Conventional flow diversion devices are in the form of a braided mesh that is designed to redirect or divert flow away from the aneurysm and along a more normal path within the vessel. The aim is to promote slow flow and stasis within the aneurysm, which over time will result in thrombus formation within the aneurysm. At a later stage the wires of the stent act as a scaffold on which a neo-endothelium (new inner lining of the vessel) can form, which completely excludes the aneurysm and allows reconstruction of the vessel. Eventually the aneurysm is completely removed from the body by its own healing mechanisms. This process takes several months and may even extend to more than one year.

Braided stents for flow diversion (flow diverter stents, FDSs) include the Silk, Pipeline, Surpass and FRED (registered trade marks of Balt Extrusion SAS, Covidien plc/Medtronic pic, Stryker Corporation and Microvention, Inc. respectively). These flow diverter stents have a relatively tight mesh, so named because their primary function is to“divert” blood flow away from the aneurysm and into the parent artery. The braiding allows for the wires of the device to slip over each other and thus elongate longitudinally when deployed in arteries that are smaller than the original diameter of the device, or vice versa if the artery diameter is greater than that of the diameter of the device.

Flow diverter stents have low-porosity - i.e. they have high metal coverage. During treatment, it is common to‘pack’ the stent at the site of the aneurysm neck (i.e. bunch the stent up), so that the metal coverage area is increased and the flow into the aneurysm reduced. However, this technique is imperfect and is highly dependent upon the skill of the operator, the type of the FDS used, and many other factors. Evidence suggests that even minimal changes can result in differences in the outcome of the treatment. Although, this tactic of packing the stent is commonly practiced, it can result in variable sizes and densities of the pore structures at the site of the neck of the aneurysm. This then can have unintended effects on the flow into the aneurysm with, for example, a jet of blood entering the aneurysm, which may then cause delayed rupture of the aneurysm. Similar effects can occur when devices bulge into aneurysms or the aneurysm is located on the outer curve of the arterial wall, all of which can result in changes in the metal coverage of the stent and hence affect its ability to occlude the aneurysm, as well as the risk of delayed rupture of the aneurysm after implantation of the FDS.

Braided stents are tubular in appearance but are made from braided wires rather than laser cut from a tubular piece of metal (as in conventional expandable stents) and are made by helically wrapping multiple wires into a tubular structure. Braided stents can be made from a nitinol or from other metals or alloys. The fundamental principles governing the design of braided stents are the device diameter, the wire diameter, and the angle that the wires make to the device axis (called the braiding angle). The rate at which the occlusion of the aneurysm occurs appears to be related to the porosity of the stents - the percentage ratio of the metal free surface area to the total surface area. This is alternatively called metal coverage area. Pore density is the number of pores per unit surface area of the device.

Early in the development of the flow diversion technique, concern was raised about the fate of covered side branches and perforators. These vessels, which can often be small but supply extremely important brain structures, are at risk if covered by stents which may then cause their occlusion. If the vessels do occlude they do so slowly over a prolonged period of time that, in general, allows an alternative blood supply to develop. However, coverage of perforators remains a concern and the acute coverage and occlusion of side branches and perforators must be avoided.

In addition to the aforementioned shortcomings of existing flow diverter devices, one must also consider the need for anti-platelet medication. The majority of existing flow diverter stents are‘bare metal stents’ which means that do not have a surface-coating of drug. Metallic stents are extremely thrombotic and will occlude within minutes if anti-platelet medication (blood thinners) are not given to the patient. Adequate inhibition of platelet function must be ensured prior to the deployment of a stent retriever in order to avoid acute occlusion and a stroke. Similarly, the patients must continue to take anti-platelet medication, typically aspirin and clopidogrel, together for 6-12 months followed by aspirin for life. These medications are known to increase the risk of gastrointestinal haemorrhage as well as increase the risk of haemorrhage elsewhere following minor trauma. There is also the increased cost and burden on the patient to ensure they continue taking the medications as failure to do so, or even taking a dangerous combination of medications which may stop the activity of the aspirin or clopidogrel, can result in acute occlusion of the flow diverter and the development of a catastrophic stroke.

Current FDSs are all based on braided wire technologies and, due to this construction, they suffer from drawbacks relating to altered pore density, sizing issues etc., that may result in inadequate treatment of the aneurysm.

There is therefore a need for a device that can alter flow and pressure within aneurysms but does not suffer from potential drawbacks related to operator skill and experience, altered pore density based on anatomical considerations of the vessels and the aneurysm, and can be easily used with little or no learning curve. Similarly, there is a need for a device that does not require the patient to take life-long anti-platelet agents, which are also a requirement of current FDSs given that they are metal and pro- thrombotic.

The present invention is directed towards a stent for use in a method for the treatment or alleviation of an aneurysm or a vessel wall deformity in an intracranial blood vessel, and the invention is also directed towards a method for the treatment or alleviation of an aneurysm or a vessel wall deformity in an intracranial blood vessel. Additionally, the invention is directed towards use of the stent in the treatment or alleviation of an aneurysm or a vessel wall deformity of an intracranial vessel. The invention is also directed towards a method for producing such a stent.

According to the invention there is provided a stent for use in a method for one of the treatment and alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the stent comprising an elongated tubular framework defining an outer circumferential surface, and an elongated diverting bore extending longitudinally therethrough for diverting blood through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and a film formed on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity.

In one embodiment of the invention the portion of the film formed on the bridging portion of the framework comprises a non-porous film. Alternatively, the portion of the film formed on the bridging portion of the framework comprises a porous film.

In another embodiment of the invention a portion of the film is formed on a non-bridging portion of the framework.

In one embodiment of the invention the portion of the film formed on the non-bridging portion of the framework comprises non-porous film. Alternatively, the portion of the film formed on the non-bridging portion of the framework comprises a porous film. In one embodiment of the invention the framework is expandable from a collapsed state to an expanded state.

In another embodiment of the invention the film is formed on the framework by coating the framework with a material in one of a liquid and powder form to form the film.

In one aspect of the invention the material in the one of the liquid and powder form to form the film is coated onto the framework by spraying. In another aspect of the invention the material in the one of the liquid and powder form to form the film is coated onto the framework by sputtering. In a further aspect of the invention the material in the one of the liquid and powder form to form the film is coated onto the framework by dipping the framework into the material in the one of the liquid and powder form to form the film. In another aspect of the invention the material in the one of the liquid and powder form to form the film is coated onto the framework by an electro-static deposition process.

Preferably, the material in the one of the liquid and powder form to form the film is configured to extend across and close the interstices of the framework at least in the bridging portion thereof when coated onto the framework. Advantageously, the material in the one of the liquid and powder form to form the film is configured to extend across and close each of the interstices of the framework when coated onto the framework.

In one embodiment of the invention the film is reinforced with a non-woven fabric. Preferably, the non- woven fabric is applied to the framework by spinning. Advantageously, the non-woven fabric is applied to the framework by electrospinning. Ideally, the non-woven fabric is applied to the framework prior to coating the framework with the film material.

Preferably, the material of the film comprises a biocompatible material.

In one embodiment of the invention the material of the film comprises a polymeric material.

In another embodiment of the invention the material of the film is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a nonpolymeric material, such as a hyperelastic thin film nitinol. In a further embodiment of the invention the material of the film comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

Preferably, the film comprises one of a film, implanted at a molecular level with a medicament and a film coated with a medicament. In one aspect of the invention the medicament comprises a medicament configured to reduce the thrombotic potential of the stent. In another aspect of the invention the medicament comprises a medicament configured to minimise growth of atherosclerotic plaque.

In one embodiment of the invention the material of the film comprises a biodegradable material.

In another embodiment of the invention the film is formed on the framework when the framework is in the expanded state.

In one embodiment of the invention the framework comprises a biocompatible material.

In another embodiment of the invention the framework comprises a memory material. Preferably, the framework comprises a metal alloy. Advantageously, the framework comprises one of an alloy of nickel and titanium, a cobalt alloy and stainless steel.

Alternatively, the framework comprises a polymer material.

In one embodiment of the invention the material of the framework is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a nonpolymeric material, such as a hyperelastic thin film nitinol.

In another embodiment of the invention the material of the framework comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

In a further embodiment of the invention the framework comprises a biodegradable material.

Preferably, the material of the framework is one of implanted and coated with a medicament. In another aspect of the invention the medicament comprises a medicament to reduce the thrombotic potential of the stent. In another aspect of the invention the medicament comprises a medicament to minimise growth of atherosclerotic plaque.

In one embodiment of the invention the framework is constructed from a tubular member, and the interstices are cut radially through the tubular member. Preferably, the interstices are formed by laser cutting of the tubular member. Advantageously, the tubular member from which the framework is formed is selected to be of diameter substantially equal to the diameter of the framework in the expanded state thereof.

In one embodiment of the invention the portion of the film formed on the bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the bridging portion thereof, each communicating opening communicating with the diverting bore.

In another embodiment of the invention the portion of the film formed on the non-bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the non-bridging portion thereof, each communicating opening in the non-bridging portion of the framework communicating with the diverting bore.

In another embodiment of the invention in the expanded state of the framework the number of the communicating openings in the film formed on the bridging portion of the framework per unit surface area of the bridging portion of the film is less than the number of communicating openings in the film formed on the non-bridging portion of the framework per unit surface area of the non-bridging portion of the film.

Preferably, in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 10% to 90% of the number of the communicating openings per unit surface area of the non-bridging portion of the film. Advantageously, in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 15% to 50% of the number of the communicating openings per unit surface area of the non-bridging portion of the film. More preferably, in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 20% to 40% of the number of the communicating openings per unit surface area of the non-bridging portion of the film. Ideally, in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film is approximately 30% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

In another aspect of the invention in the expanded state of the framework each communicating opening in the bridging portion of the film is of area less than the area of each communicating opening in the nonbridging portion of the film. Preferably, in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 5% to 90% of the area of each communicating opening in the non-bridging portion of the film. Advantageously, in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 10% to 50% of the area of each communicating opening in the non-bridging portion of the film. More preferably, in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 20% to 40% of the area of each communicating opening in the nonbridging portion of the film. Ideally, in the expanded state of the framework each communicating opening in the bridging portion of the film is of area is approximately 30% of the area of each communicating opening in the non-bridging portion of the film.

In another embodiment of the invention in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.1mm² to 1.2mm². Preferably, in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.2mm² to 1.1mm². Advantageously, in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.25mm² to 0.99mm².

Preferably, the communicating openings in the non-bridging portion of the film are configured to supply adequate blood flow to one or both of branch vessels and perforators branching from the vessel when the stent is located in the vessel.

In another embodiment of the invention the framework is of substantially cylindrical shape. Preferably, the framework in the collapsed state is of substantially constant transverse cross-section along its longitudinal length. Advantageously, the framework in the expanded state is of substantially constant transverse cross-section along its longitudinal length. In one embodiment of the invention the outer diameter of the framework in the collapsed state lies in the range of 5% to 50% of the outer diameter of the framework in the expanded state. Preferably, the outer diameter of the framework in the collapsed state lies in the range of 7.5% to 20% of the outer diameter of the framework in the expanded state. Advantageously, the outer diameter of the framework in the collapsed state is approximately 10% of the outer diameter of the framework in the expanded state.

In one embodiment of the invention the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.5mm. Preferably, the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.33mm. Ideally, the outer diameter of the framework in the collapsed state is approximately 0.3mm.

In another embodiment of the invention the outer diameter of the framework in the expanded state lies in the range of 1 mm to 5mm. Preferably, the outer diameter of the framework in the expanded state lies in the range of 2mm to 4mm. Advantageously, the outer diameter of the framework in the expanded state is approximately 3mm.

In another embodiment of the invention the film extends over substantially the entire surface area of the framework on one or both of the outer surface and the inner surface thereof.

In another embodiment of the invention the framework extends longitudinally between a first end and a second end thereof, and comprises a first non-bridging portion extending longitudinally from the first end to the bridging portion, and a second non-bridging portion extending longitudinally from the second end to the bridging portion.

Preferably, the bridging portion of the framework extends longitudinally between the first and second nonbridging portions thereof. In another embodiment of the invention the first and second non-bridging portions of the framework meet along a portion of the circumference of the framework, and together define the bridging portion.

The invention also provides a method for one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising providing a stent according to the invention, and placing the stent in the vessel with the bridging portion thereof adjacent the one of the aneurysm and the vessel wall deformity for restricting blood flow to the one of the aneurysm and the vessel wall deformity.

Additionally, the invention provides a method for one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising providing a stent comprising an elongated tubular framework defining an outer circumferential surface and an elongated diverting bore extending longitudinally therethrough for directing blood flow through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and a film formed on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity, the method further comprising placing the stent in the vessel with the bridging portion thereof adjacent the one of the aneurysm and the vessel wall deformity for restricting blood flow to the one of the aneurysm and the vessel wall deformity.

In one aspect of the invention the stent is urged through the intracranial vascular system to the vessel in a wall of which the one of the aneurysm and the vessel wall deformity is located.

In another aspect of the invention the stent is positioned in the vessel, so that when the stent is expanded in the vessel, the portion of the film formed on the bridging portion of the framework lies adjacent the one of the aneurysm and the vessel wall deformity for restricting blood flow thereto.

In a further aspect of the invention the framework, with the portion of the film formed on the bridging portion of the framework aligned with the one of the aneurysm and the vessel wall deformity, is expanded within the vessel.

Further the invention provides a method for manufacturing a stent for use in one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising forming an elongated tubular framework defining an outer circumferential surface and an elongated diverting bore extending longitudinally therethrough for diverting blood through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and forming a film on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity.

The advantages of the stent according to the invention are many. A particularly important advantage of the stent according to the invention is that it permits the blood flow to an aneurysm or a vessel wall deformity to be significantly reduced, while at the same time maintaining the normal blood flow to side branch vessels and perforators from the vessel at the respective opposite ends of the aneurysm or the vessel wall deformity. Furthermore, the stent according to the invention can be readily, easily and accurately placed in the vessel with the bridging portion of the film located adjacent the aneurysm or the vessel wall deformity, with little or no learning curve. These advantages are achieved by virtue of the fact that the area of the communicating openings in the portion of the film formed on the bridging portion of the framework is less than the area of the communicating openings in the portion of the film formed on the non-bridging portions of the framework, and also by virtue of the fact that the number of the

communicating openings per unit area in the portion of the film formed on the bridging portion of the framework is less than the number of the communicating openings per unit area in the portion of the film formed on the non-bridging portion of the framework. By forming the film on the framework of the stent by coating the film onto the framework, the film essentially becomes an integral part of the framework, and therefore, is not moveable relative to the framework. This provides the particularly important advantage that the stent can be readily, easily and accurately placed in the vessel with the bridging portion of the film adjacent the aneurysm or the vessel wall deformity, and the non-bridging portion of the film adjacent the side branch vessels and/or perforators, since once the stent is accurately positioned in the vessel, the film will be automatically accurately positioned in the vessel, and will remain so, since it is essentially an integral part of the framework, and is not moveable relative to the framework. Additionally, by providing blood flow to the aneurysm or the vessel wall deformity at a relatively low flow rate, the formation of thrombosis in the aneurysm or the vessel wall deformity is promoted, and the subsequent reconstruction of the vessel wall is enhanced.

The invention will be more clearly understood from the following description of some non-limiting preferred embodiments thereof, which are described by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view not to scale of a stent according to the invention in an expanded state for use in a method for the treatment of an aneurysm or a vessel wall deformity in an intracranial vessel,

Fig. 2 is a side elevational view not to scale of the stent of Fig. 1 in the expanded state,

Fig. 3 is a cross-sectional end elevational view not to scale of the stent of Fig. 1 on the line Ill-Ill of Fig. 2 in the expanded state but with some of the structural members of a framework of the stent omitted,

Fig. 4 is a cross-sectional side elevational view not to scale of a portion of the stent of Fig. 1 on the line IV-IV of Fig. 3 in the expanded state but with some of the structural members of the framework of the stent omitted,

Fig. 5 is a side elevational view not to scale of a tube of a memory material from which the framework of the stent of Fig. 1 is formed with the tube marked for laser cutting thereof,

Fig. 6 is a side elevational view not to scale of the framework in the expanded state of the stent of Fig. 1 laser cut from the tube of Fig. 5,

Fig. 7 is a side elevational view not to scale of the stent of Fig. 1 in a collapsed state,

Fig. 8 is a side elevational view not to scale of the stent of Fig. 1 in the expanded state in use,

Fig. 9 is a side elevational view not to scale of a stent according to another embodiment of the invention in an expanded state for use in a method for the treatment of an aneurysm in an intracranial vessel,

Fig. 10 is a side elevational view not to scale of a stent according to another embodiment of the invention in an expanded state for use in a method for the treatment of an aneurysm in an intracranial vessel,

Fig. 11 is a cross-sectional end elevational view not to scale similar to that of Fig. 3 of the stent of Fig. 10 in the expanded state on the line XI-XI of Fig. 10, and Fig. 12 is a side elevational view not to scale of the stent of Fig. 10 in the expanded state in use.

Referring to the drawings, and initially to Figs. 1 to 8 there is illustrated a stent according to the invention indicated generally by the reference numeral 1 for use in a method for one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial blood vessel. In this embodiment of the invention the stent 1 is particularly suitable for use in a method for the treatment of an aneurysm 3 in a vessel wall 4 of an intracranial blood vessel 5, and is therefore described for use in the treatment of the aneurysm 3. However, it will be readily understood that the stent 1 may be used for the treatment of or alleviation of an aneurysm or any other vessel wall deformity.

The stent 1 comprises a substantially cylindrical framework 7 extending longitudinally from a first end 9 to a second end 10, and defines a longitudinally extending central axis 12. The framework 7 defines an outer circumferential surface 14 and an inner circumferential surface 15. A diverting bore 17 extends longitudinally and centrally through the framework 7 from the first end 9 to the second end 10. The diverting bore 17 defines the inner circumferential surface 15 of the framework 7, and is provided for diverting blood flow through the vessel 5 past the aneurysm 3, as will be described below.

In this embodiment of the invention the framework 7, and in turn the stent 1 is expandable from a collapsed state illustrated in Fig. 7 to an expanded state illustrated in Figs. 1 to 6 and 8. In this embodiment of the invention the framework 7 is of closed cell construction comprising a plurality of interconnected structural members 19 defining interstices 20 therebetween extending radially through the framework 7 from the diverting bore 17 to the outer surface 14 of the framework 7. In this embodiment of the invention the stent is formed from a tube 21 of circular transverse cross-section of a memory material of diameter similar to the outer diameter of the framework 7 in the expanded state. The interstices 20 are laser cut from the tube 21 , leaving the structural members 19 in the tube 21 to form the framework 7 in its expanded state, so that the framework 7 can be collapsed from the expanded state to the collapsed state. The framework 7 being of a memory material which when released from the collapsed state, expands to the expanded state to be of diameter similar to the original diameter of the tube 21 when released in the blood vessel 5. In Fig. 5 the tube 21 is marked to show the parts 23 of the tube 21 to be laser cut therefrom. Fig. 6 illustrates the tube 21 with the parts 23 laser cut therefrom to form the framework 7 in the expanded state.

In this embodiment of the invention the memory material of the framework 7 comprises a memory metal which in this case comprises an alloy of nickel and titanium. The wall thickness of the tube of memory metal is selected so that the framework 7 is sufficiently flexible between its first and second ends 9 and 10 to facilitate bending of the framework 7 in the collapsed state during delivery of the stent 1 to the vessel 5, and also in the expanded state to facilitate deployment in a vessel 5 of curved shape.

The framework, instead of being of a closed cell construction may also be of an open cell construction.

The manufacture of such closed and open cell construction stent frameworks will be well known to those skilled in the art. Alternatively, the stent framework may be of a braided construction formed by a plurality of spaced apart helically wound wires, helically wound in opposite directions to each other in order to define interstices therebetween extending from a centrally extending diverting bore radially through the interstices to the outer surface of the braiding of the stent. Additionally, as will be discussed below the framework may comprise any other metal material or metal alloy or may comprise a polymer material.

A film 22 of a polymer material is formed on the framework 7 over the entire area thereof. The film 22 is formed on the framework 7 by coating the outer and inner surfaces 14 and 15 of the framework 7 with the polymer material in liquid or powder form and then subsequently curing the coated film. In this embodiment of the invention the polymer material of a relatively viscous liquid form of the material which is sprayed or sputtered onto the framework 7 in the expanded state. The viscosity of the polymer material is such that the film 22 when coated onto the framework 7 completely closes the interstices 20 of the framework 7, see in particular Figs. 3 and 4. Additionally, the polymer material of the film 22 is implanted with a medicament, and in this embodiment of the invention the polymer material of the film 22 is implanted with two medicaments, one to reduce the thrombotic potential of the stent, and the other to minimise growth of atherosclerotic plaque. However, as will be discussed below the film 22 may be of any other suitable material and may be applied to or coated onto the framework 7 by any other suitable process.

In this embodiment of the invention the stent 1 , and in turn the framework 7, defines a bridging portion for bridging the aneurysm 3, which in this embodiment of the invention comprises a central bridging portion 25 which extends longitudinally over a length of the framework 7, see Fig. 2. A first non-bridging portion 26 of the stent 1 , and in turn the framework 7, extends from the first end 9 of the stent 1 longitudinally to the central bridging portion 25 for a longitudinal distance L₂. A second non-bridging portion 27 of the stent 1 , and in turn the framework 7, extends longitudinally from the second end 10 of the stent 1 to the central bridging portion 25 over a longitudinal distance L₃, so that the central bridging portion 25 is defined between the first and second portions 26 and 27.

In this embodiment of the invention a plurality of communicating openings 29 extend through the film 22 in the interstices 20 and communicate with the diverting bore 17. For convenience, the communicating openings 29 extending through the film 22 in the central bridging portion 25 are referred to as first communicating openings 29a, and the communicating openings extending through the film 22 in the first and second non-bridging portions 26 and 27 are referred to as second communicating openings 29b.

The number of first communicating openings 29a per unit area extending through the film 22 in the central bridging portion 25 is less than the number of second communicating openings 29b extending through the film 22 in the first and second non-bridging portions 26 and 27, in order to restrict blood flow to the aneurysm 3 from the diverting bore 17. Additionally, the area of the first communicating openings 29a is less than the area of the second communicating openings 29b, similarly, to restrict blood flow to the aneurysm 3 from the diverting bore 17.

In this embodiment of the invention the number of second communicating openings 29b in the first and second non-bridging portions 26 and 27 of the stent 1 is similar to the number of interstices 20 extending through the first and second non-bridging portions 26 and 27. In other words, one second communicating opening 29b extends through the film 22 in each interstice 20 of the framework 7 in the first and second non-bridging portions 26 and 27. The number of first communicating openings 29a per unit area extending through the film 22 in the central bridging portion 25 is approximately thirty percent of the number of second communicating openings 29b per unit are extending through the film 22 in the first and second non-bridging portions 26 and 27. In other words, only one first communicating opening 29a extends through every third interstices 20 of the framework 7 in the central bridging portion 25 thereof both longitudinally along the framework 7 and circumferentially around the framework 7.

The area of the communicating openings 29, in general, lies in the range of 0.25mm² to 0.9mm² when the stent 1 and in turn the framework 7 are in the expanded state, the first communicating openings 29a being at the lower end of the range, and the second communicating openings 29b being at the upper end of the range. The area of each first communicating opening 29a lies in the range of 5% to 90% of the area of each second communicating opening 29b, and more typically, the area of each first communicating opening 29a lies in the range of 10% to 50% of the area of each second communicating opening 29b, most typically, the area of each first communicating opening 29a is approximately 30% of the area of each second communicating opening 29b.

The provision of the second communicating openings 29b extending through the film 22 in the first and second non-bridging portions 26 and 27 being of greater area than the first communicating openings 29a, and the provision of the number of second communicating openings 29b per unit area extending through the film 22 in the first and second non-bridging portions 26 and 27 being greater than the number of the first communicating openings 29a per unit area extending through the film 22 in the central bridging portion 25 provides and maintains a supply of blood to side branches 30 and perforators 31 extending from the vessel 5 at respective opposite ends of the aneurysm 3, see Fig. 8.

The area of the first communicating openings 29a and the number of the first communicating openings 29a per unit area of the film 22 in the central bridging portion 25 will be dependent on the nature and size of the aneurysm 3 and the area of the opening in the vessel wall 4 to the aneurysm 3. The area of the second communicating openings 29b and the number of the second communicating openings 29b per unit area of the film 22 in the first and second non-bridging portions 26 and 27 will be dependent on the number and size of the branch vessels 30 and the perforators 31 extending from the vessel 5 at the respective opposite ends of the aneurysm 3 which are likely to be in the area covered by the first and second non-bridging portions 26 and 27 of the stent 1. A pusher wire 34 is releasably secured to the first end 9 of the framework 7 of the stent 1 in order to facilitate deployment of the stent 1 in the vessel 5, and for urging the stent 1 through a delivery bore of a delivery catheter (not shown) to the vessel 5, and also for urging the stent 1 from the delivery bore of the delivery catheter into the vessel 5, and for facilitating final positioning of the stent 1 in the vessel 5. The pusher wire 34 is releasably coupled to the framework 7 by a releasable coupling 35. Any suitable releasable coupling 35 for coupling the pusher wire 34 to the framework 7 may be provided, and such releasable couplings for coupling a pusher wire to a framework of a stent will be well known to those skilled in the art.

In use, with the pusher wire 34 connected to the first end 9 of the framework 7, the stent 1 in the collapsed state is urged through a delivery catheter (not shown), which has been urged through the intracranial vascular system with the distal end of the delivery catheter terminating in the vessel 5 adjacent the aneurysm 3. The stent 1 is urged by the pusher wire 34 through a delivery bore of the delivery catheter (not shown) until the stent 1 is located within the delivery bore of the delivery catheter adjacent the distal end thereof, so that the stent 1 is positioned relative to the vessel with the central bridging portion 25 adjacent and bridging the aneurysm 3. The stent 1 is held in position by the pusher wire 34 and the delivery catheter is withdrawn sufficiently to expose the stent 1 in the vessel 5. On exposing of the stent 1 in the vessel 5, the stent 1 expands from its collapsed state to its expanded state thereby engaging the inner surface of the vessel wall 4 of the vessel 5 with the central bridging portion 25 of the stent 1 adjacent and bridging the aneurysm 3, and essentially isolating the aneurysm 3 from the vessel 5 apart from the first communicating openings 29a. Once the stent 1 is correctly positioned in the vessel 5, the pusher wire 34 is released therefrom, and the delivery catheter with the pusher wire within the delivery bore of the delivery catheter is withdrawn from the intracranial vascular system.

While the central bridging portion 25 of the stent 1 does not entirely prevent blood flow from the diverting bore 17 into the aneurysm 3, the rate of blood flow from the diverting bore 17 to the aneurysm 3 through the first communicating openings 29a is significantly limited, thereby promoting thrombosis formation within the aneurysm. This in turn results in healing of the vessel wall 4 adjacent the aneurysm 3 after a period of several months to more than one year, which results in the aneurysm 3 eventually being removed from the vessel by the normal healing mechanism of the body of a subject. The first and second non-bridging portions 26 and 27 of the stent 1 facilitate and maintain blood flow through the second communicating openings 29b in the film 22 to the side branch vessels 30 and the perforators 31 extending from the vessel 5 at the respective opposite ends of the aneurysm 3, without limiting the blood supply to the side branch vessels 30 and the perforators 31.

The tube of memory metal from which the framework 7 is laser cut is selected to be of diameter suitable for the vessel in which the stent 1 is to be located. The diameter of the tube of memory metal should be of diameter such that when the stent 1 expands in the vessel 5, the outer diameter of the expanded stent 1 should be sufficient to tightly abut the inner surface of the vessel wall 4 of the vessel 5. Once laser cut from the tube of memory metal, the framework 7 is then collapsed into its collapsed state, and remains in the collapsed state until it is required. The stent 1 is entered into the delivery bore of the delivery catheter in its collapsed state, and remains in its collapsed state until it is urged from the delivery catheter into the vessel 5, and is exposed to the blood temperature in the vessel 5. At which stage the stent 1 expands to its expanded state. Typically, the stent 1 according to the invention in its expanded state will be of outer diameter f-i in the range of 2mm to 5mm, and in its collapsed state in order to facilitate urging through a delivery bore of a delivery catheter, the stent 1 will typically be of outer diameter f₂ in the range of 0.25mm to 0.5mm.

While the framework 7 of the stent 1 has been described as comprising a memory metal, the framework 7 may be of any other suitable material, and may be of a material which is suitable for delivery to the vessel on a balloon catheter with the stent 1 in its collapsed state mounted on the balloon of the balloon catheter with the balloon deflated. On delivery of the stent into the vessel, the balloon of the balloon catheter would then be inflated to expand the stent 1 to tightly engage the wall of the vessel.

Additionally, while the framework 7 has been described as comprising a metal material, the framework 7 of the stent 1 may be of any suitable material. However, when comprising a metal, the metal of the framework will be of a suitable biocompatible metal. It is also envisaged that the framework 7 of the stent 1 may be of a polymer material, which would be biocompatible, and may also be biodegradable, and if biodegradable would have a limited lifespan, but would remain in place until it dissolved, and ideally, the framework 7 would be of a material which would not dissolve in the vessel for at least twelve months, and preferably, twenty-four months, and in some cases even longer than twenty-four months.

Suitable polymer-based materials which would be suitable for the framework 7 are, for example, poly(L- lactide) (PLLA), which is suitable for maintaining a radially strong framework and breaks down over time into lactic acid, a naturally occurring molecule that the body can safely metabolise. Other suitable polymers include tyrosine polycarbonate and salicylic acid-derived polymers. The timing of the degradation allows the reconstruction of the arterial wall and exclusion of the aneurysm but also the removal of the stent such that no medications would be required and there would be no effect of the stent during medical imaging such as MRI or conventional CT scanning of the brain or other treated organs. The polymer material of the film 22 suitably comprises a polymeric material, such as polyurethane, polytetrafluoroethylene, polyester, polyamide or polyolefin. Non-polymeric materials, such as a hyperelastic thin film nitinol, are also suitable.

It is also envisaged that the film 22 may be reinforced with a non-woven fabric. In which case, it is envisaged that a precursor of polymer material compatible with the material of the framework 7 of the stent 1 would be sprayed onto the framework. A non-woven fabric would then be applied to the framework by electrospinning onto the structural members 19 of the framework 7. By applying an electric current, the fibrils of the film 22 are separated from a polymer solution and deposited on a substrate. The technique of electrospinning is well known in the art, and further description should not be required. The deposition causes the fibrils to agglutinate into a non-woven fabric which can be formed into strands that can be woven if chosen. The fibrils generally have a diameter of from 10Onm to 10OOnm. The formation of the film 22 by electrospinning provides a relatively thin film 22 of substantially uniform thickness which readily forms a bond with the framework 7 of the stent. Such a film is sufficiently strong to withstand mechanical stress during compression of the stent into the collapsed state, and during manoeuvring of the stent into the vessel. Such a film may be easily mechanically pierced to form the communicating openings, without creating an opening that would give rise to fractures or cracks. The thickness and length of the fibrils can be controlled by the electrospinning process. Examples of such films or membranes include poly(lactide-co-caprolactone) (PLCL) which can have a degradation time of 6-18 months; poly(caprolactone) (PCL) which can have a degradation time of 2-3 years; or stiffer materials such as polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitrile (PAN) or polyurethane (PU).

Advantageously, the film 22 is soft and elastic such that with the blood flow in the artery it will be pushed against the walls of the arteries, which will assist in preventing endoleaks - leaks of blood around the stent, as well as assisting in the formation of neo-endothelium.

The film 22 can be composed of a single layer or multiple layers. Multiple layers may be produced by different methods, for example the first layer by electrospinning, the second by spray coating and the third by electrospinning. Active pharmaceutical or other agents can be implanted on one or several of these layers. The agent can be released by diffusion or by degradation or erosion of the layers of film.

Radiopaque substances can also be implanted in the film 22 so that it is more easily visible to the techniques used during stent implantation. The film 22 may be laced with graphene to improve its strength and flexibility.

The film 22 may or may not be perforated. The film 22 may or may not comprise a non-woven fabric made of plastic fibrils.

The biocompatible film may be perforated mechanically, such as with a laser (for example a femtosecond laser), or by any other method capable of perforating the film in a uniform repeated pattern so as to create a semi-permeable film that will allow continued blood flow into covered side branched and perforator arteries. The size of the perforations can be controlled as can the space between the perforations to allow for devices intended for different anatomical locations, for example, in the perforator rich posterior circulation the perforations could be slightly larger and for devices intended for the cavernous segment of the internal carotid artery very small perforations could be formed. Accordingly, the stent 1 may be tailored to specific anatomical regions, thereby enhancing patient outcomes. Alternatively, an electrospun film can be made with an appropriate porosity for blood. The porosity of the film can be varied along its length such that portions of the film covering side branch vessels and perforators are significantly more permeable to blood flow, than the portion bridging the aneurysm, so that side branch vessels and perforators covered by the film are adequately supplied with blood flow, while the portion of the film bridging the aneurysm which is less permeable to blood flow would result in significantly greater reduction in blood flow to the aneurysms.

The size of the communicating openings 29, and the distance between the communicating openings 29 can be altered but the size of the communicating openings 29 in the film 22 will typically range from 0.25mm² to 0.99mm² for example. The distance between the communicating openings 29 can also be adjusted and can be, typically, from 0.1mm to 1 mm. In addition, the size of the communications openings 29 and the distance between the communication openings 29 can be varied along the film 22 and along the stent 1 such that a gradient can be created with certain areas representing greater or lesser porosity. This can be useful in order to minimize aneurysmal inflow particularly at the edges of the aneurysmal neck, which may be more dangerous than inflow into the aneurysm occurring from the central portion of the aneurysmal neck.

Equally, the film 22 attached to the framework can be made from woven electrospun fibres. A sheet of woven fibre is formed, similar to woven cloth, and the sheet is then attached to the underlying stent construct or woven around the stent structure.

The film 22 may be attached to the stent 1 with an organic agglomerate or the film 22 may be spun directly onto and over the struts of the stent 1. A spun film effectively excludes the metal of the framework 7 from the circulation which results in a lower thrombogenic potential and can reduce the risk of thrombi formation and ischemic complications as well as in-stent thrombosis.

Maintaining flow in the side branches and/or perforators will prevent infarcts from occurring. The size of the communicating openings 29 can be tailored to provide optimum flow reduction within a particular aneurysm whilst maintaining flow into the side branches. The uniform nature of this construction minimizes the impact of altering size of the communicating openings and porosity based on arterial anatomy, operator technique and so on. Therefore, the stent design of the present invention provides a more stable, uniform and consistent construction with no change in porosity, unlike traditional braided mesh design FDS constructions, which are subject to the disadvantages discussed above.

Furthermore, in certain embodiments, the thickness of film may be varied to provide a thicker film 22 at certain points along the stent. Similarly, the film 22 may be designed to allow puncture with a standard microwire and microcatheter 20 such that, if the aneurysm fails to occlude, the film 22 may be punctured and the aneurysm treated with standard intrasaccular devices such as coils.

Referring now to Fig. 9 there is illustrated a stent according to another embodiment of the invention and indicated generally by the reference numeral 40 for use in a method according to the invention for the treatment of an aneurysm in an intracranial vessel. The stent 40 is substantially similar to the stent 1 , and similar components are identified by the same reference numerals. The only differences between the stent 40 and the stent 1 are that the first non-bridging portion 26 is longer than the second non-bridging portion 27, and an aperture 41 is formed in the framework 7 in the first non-bridging portion 26 of the framework 7. The aperture 41 is of area sufficient to prevent the formation of the film 22 over and across the area of the aperture 41. Accordingly, the aperture 41 in the first non-bridging portion 26 of the stent 1 communicates the diverting bore 17 with the exterior of the stent 1. When the stent 1 is located in and expanded in a vessel 5 with a relatively large side branched vessel extending from the vessel in which the aneurysm 3 is located, by aligning the aperture 41 with the relatively large branched vessel, blood flow is supplied to the branched vessel from the diverting bore 17 through the aperture 41. The aperture 41 may be of any suitable area, and typically, would be of area in the range of 1 mm to 3mm.

Otherwise, the stent 40 and its use is similar to that of the stent 1.

Referring now to Figs. 10 to 12, there is illustrated a stent according to another embodiment of the invention indicated generally by the reference numeral 50 which is also for use in a method for the treatment of an aneurysm 3 in an intracranial vessel 5, substantially similar to that described with reference to Fig. 8. The stent 50 is substantially similar to the stent 1 , and similar components are identified by the same reference numerals. The only differences between the stent 50 and the stent 1 is that like the stent 40, the first non-bridging portion 26 is longer than the second non-bridging portion 27, and also in this embodiment of the invention the first and second non-bridging portions 26 and 27 meet intermediate the first and second ends 9 and 10 of the stent 50 at 51 along a part of the circumference of the stent 50 for an angular distance a of approximately 120°. Accordingly, in this embodiment of the invention the central bridging portion 25 of the stent 1 does not extend completely circumferentially around the stent 1 , but rather, for a circumferential angular distance Q of 240°, which is equal to 360° - a.

Accordingly, in this embodiment of the invention the central bridging portion 25 is defined by the first and second non-bridging portions 26 and 27 of the stent 1.

In use, the stent 50 is located in the vessel with the central bridging portion 25 adjacent the aneurysm 3. Otherwise, the stent 50 and its use is similar to that of the stent 1.

The advantage of the stent 50 according to this embodiment of the invention is that if there are side branch vessels 30 and/or perforators 31 extending from the vessel 5 opposite the aneurysm 3 as illustrated in Fig. 12, these branch vessels and perforators are supplied with blood flow from the communicating openings 29b in the first and second non-bridging portions 26 and 27 in the stent 1 which are diametrically opposite to the central bridging portion 25.

The film 22 may optionally be implanted or coated with one or more pharmaceutical compositions or other compositions having a desirable effect on the properties of stents 1 , 40 and 50. This addresses the challenge of coating stent surfaces with pharmaceutical materials. These compositions can release medication over time into the surrounding tissues, vascular surface or plaques. Proliferation-inhibiting substances such as paclitaxel and rapamycin, for example, could be beneficial. Other examples are substances that prevent thrombosis, or prevent liquid embolic agents or glue from adhering to the film or membrane and/or the stent.

The films 22 may be impregnated with nanoparticles for drug delivery, targeted towards preventing thrombosis or anti-atherosclerosis medication to prevent progression of atherosclerotic plaques. A layer- by-layer assembly of the films 22 may also be designed to achieve controlled release of medication from the polymers. Other medication techniques, such as gene-modifying eluting, will be possible.

Accurate deployment of the stents according to the invention may be obtained via appropriately positioned radio-opaque markers which are visible under x-ray fluoroscopy, as is known in the art. Optionally, markers may be provided at the first and second ends of the stents 1 , 40 and 50. Alternatively, or additionally, the central bridging portions of stents 1 , 40 and 50 may be made more radio-opaque, for example by the application of a gold coating to the structural members for better visibility of apposition to the wall of the vessel. Similarly, the stents 1 , 40 and 50 may be coated substantially in their entirety with a radio-opaque marker such as gold.

Anti-platelet therapy is frequently recommended for patients that have received a stent. In the case that the stents comprise a biodegradable material, anti-platelet medication can be discontinued after dissolution of the stent.

Accordingly, in general terms, the present invention provides, in one aspect, fully retrievable stents with a biocompatible film. The biocompatible film may be of an electrospun membrane with communicating openings 29, made either mechanically, with a laser, or using another suitable method, that allows for a pre-determined and repeating pattern to be produced within either part or all of the film such that blood flow through the film (and hence through the stent) can be controlled, such that blood flow to side branch vessels and perforators is not blocked, and blood flow to an aneurysm is, at least partially, blocked. This allows the stents to behave as flow diverters so that they can be used to treat aneurysms. The film and stent structure can also be designed in such a way that larger holes are present that allow another stent to be deployed through the first one and enable a Y or T stent configuration to be formed which is useful in the treatment of bifurcation aneurysms.

The framework onto which the film is formed may be based on a standard open or closed cell stent configuration.

While the film has been described as extending completely over the framework of each of the stents according to the invention, it will be readily apparent to those skilled in the art that it is not essential that the film should extend completely over the entire area of the framework, in some embodiments of the invention it may extend over only a part of the area of the framework of the stent, and indeed, it is envisaged that in some embodiments of the invention the film may only extend over the bridging portion of the framework of the stent. While the film has been described as being coated onto both the inner and outer circumferential surfaces of the framework, it is envisaged that in some embodiments of the invention the film may be coated over only one of the surfaces of the framework of the stent, for example, the film may be coated on only the outer circumferential surface, or the inner circumferential surface of the framework of the stent.

While the stents according to the invention have been described for use in a method for the treatment or alleviation of an aneurysm in an intracranial vessel, it will be readily apparent to those skilled in the art that the stents according to the invention may be used for the treatment or alleviation of any other vessel wall deformity in an intracranial vessel.

While in the embodiments of the stent described with reference to Figs. 1 to 12, the film has been described as closing all the interstices of the framework, it is envisaged that in some embodiments of the invention the film may not necessarily close all the interstices in the framework, and in some embodiments, may only close the interstices of the bridging portion of the framework. It is also envisaged that the film may be formed on the framework so that the communicating openings are formed during the coating of the film on the framework, and in particular, it is envisaged that the second openings 29b may be formed during coating of the film onto the framework. This would avoid the need to form the openings in the film subsequent to forming the film on the framework. It is also envisaged that depending on the area of the interstices of the framework, in some cases more than one communicating opening may be formed in each interstices, particularly, in the first and second non-bridging portions of the framework. Needless to say, it will be appreciated that in some embodiments of the invention a first communicating opening may be provided in the film in each of the interstices in the central bridging portion of the framework.

Claims

1. A stent for use in a method for one of the treatment and alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the stent comprising an elongated tubular framework defining an outer circumferential surface, and an elongated diverting bore extending longitudinally therethrough for diverting blood through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and a film formed on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity.

2. A stent as claimed in Claim 1 in which the portion of the film formed on the bridging portion of the framework comprises a non-porous film.

3. A stent as claimed in Claim 1 in which the portion of the film formed on the bridging portion of the framework comprises a porous film.

4. A stent as claimed in any preceding claim in which a portion of the film is formed on a non- bridging portion of the framework.

5. A stent as claimed in Claim 4 in which the portion of the film formed on the non-bridging portion of the framework comprises non-porous film.

6. A stent as claimed in Claim 4 in which the portion of the film formed on the non-bridging portion of the framework comprises a porous film.

7. A stent as claimed in any preceding claim in which the framework is expandable from a collapsed state to an expanded state.

8. A stent as claimed in any preceding claim in which the film is formed on the framework by coating the framework with a material in one of a liquid and powder form to form the film.

9. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is coated onto the framework by spraying.

10. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is coated onto the framework by sputtering.

11. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is coated onto the framework by dipping the framework into the material in the one of the liquid and powder form to form the film.

12. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is coated onto the framework by an electro-static deposition process.

13. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is configured to extend across and close the interstices of the framework at least in the bridging portion thereof when coated onto the framework.

14. A stent as claimed in any preceding claim in which the material in the one of the liquid and powder form to form the film is configured to extend across and close each of the interstices of the framework when coated onto the framework.

15. A stent as claimed in any preceding claim in which the film is reinforced with a non-woven fabric.

16. A stent as claimed in Claim 15 in which the non-woven fabric is applied to the framework by spinning.

17. A stent as claimed in Claim 15 or 16 in which the non-woven fabric is applied to the framework by electrospinning.

18. A stent as claimed in any of Claims 15 to 17 in which the non-woven fabric is applied to the framework prior to coating the framework with the film material.

19. A stent as claimed in any preceding claim in which the material of the film comprises a biocompatible material.

20. A stent as claimed in any preceding claim in which the material of the film comprises a polymeric material.

21. A stent as claimed in any preceding claim in which the material of the film is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a non-polymeric material, such as a hyperelastic thin film nitinol.

22. A stent as claimed in any preceding claim in which the material of the film comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

23. A stent as claimed in any preceding claim in which the film comprises one of a film, implanted at a molecular level with a medicament and a film coated with a medicament.

24. A stent as claimed in Claim 23 in which the medicament comprises a medicament configured to reduce the thrombotic potential of the stent.

25. A stent as claimed in Claim 23 or 24 in which the medicament comprises a medicament configured to minimise growth of atherosclerotic plaque.

26. A stent as claimed in any preceding claim in which the material of the film comprises a biodegradable material.

27. A stent as claimed in any preceding claim in which the film is formed on the framework when the framework is in the expanded state.

28. A stent as claimed in any preceding claim in which the framework comprises a biocompatible material.

29. A stent as claimed in any preceding claim in which the framework comprises a memory material.

30. A stent as claimed in any preceding claim in which the framework comprises a metal alloy.

31. A stent as claimed in any preceding claim in which the framework comprises one of an alloy of nickel and titanium, a cobalt alloy and stainless steel.

32. A stent as claimed in any preceding claim in which the framework comprises a polymer material.

33. A stent as claimed in any preceding claim in which the material of the framework is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a nonpolymeric material, such as a hyperelastic thin film nitinol.

34. A stent as claimed in any preceding claim in which the material of the framework comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

35. A stent as claimed in any preceding claim in which the framework comprises a biodegradable material.

36. A stent as claimed in any preceding claim in which the material of the framework is one of implanted and coated with a medicament.

37. A stent as claimed in Claim 36 in which the medicament comprises a medicament to reduce the thrombotic potential of the stent.

38. A stent as claimed in Claim 36 or 37 in which the medicament comprises a medicament to minimise growth of atherosclerotic plaque.

39. A stent as claimed in any preceding claim in which the framework is constructed from a tubular member, and the interstices are cut radially through the tubular member.

40. A stent as claimed in Claim 39 in which the interstices are formed by laser cutting of the tubular member.

41. A stent as claimed in Claim 39 or 40 in which the tubular member from which the framework is formed is selected to be of diameter substantially equal to the diameter of the framework in the expanded state thereof.

42. A stent as claimed in any preceding claim in which the portion of the film formed on the bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the bridging portion thereof, each communicating opening communicating with the diverting bore.

43. A stent as claimed in any preceding claim in which the portion of the film formed on the nonbridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the non-bridging portion thereof, each communicating opening in the non-bridging portion of the framework communicating with the diverting bore.

44. A stent as claimed in Claim 42 or 43 in which in the expanded state of the framework the number of the communicating openings in the film formed on the bridging portion of the framework per unit surface area of the bridging portion of the film is less than the number of communicating openings in the film formed on the non-bridging portion of the framework per unit surface area of the non-bridging portion of the film.

45. A stent as claimed in any of Claims 42 to 44 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 10% to 90% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

46. A stent as claimed in any of Claims 42 to 45 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 15% to 50% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

47. A stent as claimed in any of Claims 42 to 46 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 20% to 40% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

48. A stent as claimed in any of Claims 42 to 47 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film is approximately 30% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

49. A stent as claimed in any of Claims 42 to 48 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area less than the area of each communicating opening in the non-bridging portion of the film.

50. A stent as claimed in any of Claims 42 to 49 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 5% to 90% of the area of each communicating opening in the non-bridging portion of the film.

51. A stent as claimed in any of Claims 42 to 50 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 10% to 50% of the area of each communicating opening in the non-bridging portion of the film.

52. A stent as claimed in any of Claims 42 to 51 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 20% to 40% of the area of each communicating opening in the non-bridging portion of the film.

53. A stent as claimed in any of Claims 42 to 52 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area is approximately 30% of the area of each communicating opening in the non-bridging portion of the film.

54. A stent as claimed in any of Claims 42 to 53 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.1mm² to 1.2mm².

55. A stent as claimed in any of Claims 42 to 54 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.2mm² to 1.1 mm².

56. A stent as claimed in any of Claims 42 to 55 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.25mm² to 0.99mm².

57. A stent as claimed in any of Claims 42 to 56 in which the communicating openings in the non- bridging portion of the film are configured to supply adequate blood flow to one or both of branch vessels and perforators branching from the vessel when the stent is located in the vessel.

58. A stent as claimed in any preceding claim in which the framework is of substantially cylindrical shape.

59. A stent as claimed in any preceding claim in which the framework in the collapsed state is of substantially constant transverse cross-section along its longitudinal length.

60. A stent as claimed in any preceding claim in which the framework in the expanded state is of substantially constant transverse cross-section along its longitudinal length.

61. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state lies in the range of 5% to 50% of the outer diameter of the framework in the expanded state.

62. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state lies in the range of 7.5% to 20% of the outer diameter of the framework in the expanded state.

63. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state is approximately 10% of the outer diameter of the framework in the expanded state.

64. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.5mm.

65. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.33mm.

66. A stent as claimed in any preceding claim in which the outer diameter of the framework in the collapsed state is approximately 0.3mm.

67. A stent as claimed in any preceding claim in which the outer diameter of the framework in the expanded state lies in the range of 1mm to 5mm.

68. A stent as claimed in any preceding claim in which the outer diameter of the framework in the expanded state lies in the range of 2mm to 4mm.

69. A stent as claimed in any preceding claim in which the outer diameter of the framework in the expanded state is approximately 3mm.

70. A stent as claimed in any preceding claim in which the film extends over substantially the entire surface area of the framework on one or both of the outer surface and the inner surface thereof.

71. A stent as claimed in any preceding claim in which the framework extends longitudinally between a first end and a second end thereof, and comprises a first non-bridging portion extending longitudinally from the first end to the bridging portion, and a second non-bridging portion extending longitudinally from the second end to the bridging portion.

72. A stent as claimed in any preceding claim in which the bridging portion of the framework extends longitudinally between the first and second non-bridging portions thereof.

73. A stent as claimed in any preceding claim in which the first and second non-bridging portions of the framework meet along a portion of the circumference of the framework, and together define the

bridging portion.

74. A method for one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising providing a stent as claimed in any preceding claim, and placing the stent in the vessel with the bridging portion thereof adjacent the one of the

aneurysm and the vessel wall deformity for restricting blood flow to the one of the aneurysm and the vessel wall deformity.

75. A method for one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising providing a stent comprising an elongated tubular framework defining an outer circumferential surface and an elongated diverting bore extending longitudinally therethrough for directing blood flow through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and a film formed on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity, the method further comprising placing the stent in the vessel with the bridging portion thereof adjacent the one of the aneurysm and the vessel wall deformity for restricting blood flow to the one of the aneurysm and the vessel wall deformity.

76. A method as claimed in Claim 74 or 75 in which the stent is urged through the intracranial vascular system to the vessel in a wall of which the one of the aneurysm and the vessel wall deformity is located.

77. A method as claimed in any of Claims 74 to 76 in which the stent is positioned in the vessel, so that when the stent is expanded in the vessel, the portion of the film formed on the bridging portion of the framework lies adjacent the one of the aneurysm and the vessel wall deformity for restricting blood flow thereto.

78. A method as claimed in any of Claims 74 to 77 in which the framework, with the portion of the film formed on the bridging portion of the framework aligned with the one of the aneurysm and the vessel wall deformity, is expanded within the vessel.

79. A method as claimed in any of Claims 74 to 78 in which the portion of the film formed on the bridging portion of the framework comprises a non-porous film.

80. A method as claimed in any of Claims 74 to 78 in which the portion of the film formed on the bridging portion of the framework comprises a porous film.

81. A method as claimed in any of Claims 74 to 80 in which a portion of the film is formed on a nonbridging portion of the framework.

82. A method as claimed in Claim 81 in which the portion of the film formed on the non-bridging portion of the framework comprises non-porous film.

83. A method as claimed in Claim 81 in which the portion of the film formed on the non-bridging portion of the framework comprises a porous film.

84. A method as claimed in any of Claims 74 to 83 in which the framework is expandable from a collapsed state to an expanded state.

85. A method as claimed in any of Claims 74 to 84 in which the film is formed on the framework by coating the framework with a material in one of a liquid and powder form to form the film.

86. A method as claimed in any of Claims 74 to 85 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by spraying.

87. A method as claimed in any of Claims 74 to 86 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by sputtering.

88. A method as claimed in any of Claims 74 to 87 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by dipping the framework into the material in the one of the liquid and powder form to form the film.

89. A method as claimed in any of Claims 74 to 88 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by an electro-static deposition process.

90. A method as claimed in any of Claims 74 to 89 in which the material in the one of the liquid and powder form to form the film is configured to extend across and close the interstices of the framework at least in the bridging portion thereof when coated onto the framework.

91. A method as claimed in any of Claims 74 to 90 in which the material in the one of the liquid and powder form to form the film is configured to extend across and close each of the interstices of the framework when coated onto the framework.

92. A method as claimed in any of Claims 74 to 91 in which the film is reinforced with a non-woven fabric.

93. A method as claimed in Claim 92 in which the non-woven fabric is applied to the framework by spinning.

94. A method as claimed in Claim 92 or 93 in which the non-woven fabric is applied to the framework by electrospinning.

95. A method as claimed in any of Claims 92 to 94 in which the non-woven fabric is applied to the framework prior to coating the framework with the film material.

96. A method as claimed in any of Claims 74 to 95 in which the material of the film comprises a biocompatible material.

97. A method as claimed in any of Claims 74 to 96 in which the material of the film comprises a polymeric material.

98. A method as claimed in any of Claims 74 to 97 in which the material of the film is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a nonpolymeric material, such as a hyperelastic thin film nitinol.

99. A method as claimed in any of Claims 74 to 98 in which the material of the film comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

100. A method as claimed in any of Claims 74 to 99 in which the film comprises one of a film, implanted at a molecular level with a medicament and a film coated with a medicament.

101. A method as claimed in Claim 100 in which the medicament comprises a medicament configured to reduce the thrombotic potential of the stent.

102. A method as claimed in Claim 100 or 101 in which the medicament comprises a medicament configured to minimise growth of atherosclerotic plaque.

103. A method as claimed in any of Claims 74 to 102 in which the material of the film comprises a biodegradable material.

104. A method as claimed in any of Claims 74 to 103 in which the film is formed on the framework when the framework is in the expanded state.

105. A method as claimed in any of Claims 74 to 104 in which the framework comprises a biocompatible material.

106. A method as claimed in any of Claims 74 to 105 in which the framework comprises a memory material.

107. A method as claimed in any of Claims 74 to 106 in which the framework comprises a metal alloy.

108. A method as claimed in any of Claims 74 to 107 in which the framework comprises one of an alloy of nickel and titanium, a cobalt alloy and stainless steel.

109. A method as claimed in any of Claims 74 to 108 in which the framework comprises a polymer material.

110. A method as claimed in any of Claims 74 to 109 in which the material of the framework is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a non-polymeric material, such as a hyperelastic thin film nitinol.

111. A method as claimed in any of Claims 74 to 110 in which the material of the framework comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

112. A method as claimed in any of Claims 74 to 111 in which the framework comprises a biodegradable material.

113. A method as claimed in any of Claims 74 to 112 in which the material of the framework is one of implanted and coated with a medicament.

114. A method as claimed in Claim 113 in which the medicament comprises a medicament to reduce the thrombotic potential of the stent.

115. A method as claimed in Claim 113 or 114 in which the medicament comprises a medicament to minimise growth of atherosclerotic plaque.

116. A method as claimed in any of Claims 74 to 115 in which the framework is constructed from a tubular member, and the interstices are cut radially through the tubular member.

117. A method as claimed in Claim 116 in which the interstices are formed by laser cutting of the tubular member.

118. A method as claimed in Claim 116 or 117 in which the tubular member from which the framework is formed is selected to be of diameter substantially equal to the diameter of the framework in the expanded state thereof.

119. A method as claimed in any of Claims 74 to 118 in which the portion of the film formed on the bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the bridging portion thereof, each communicating opening communicating with the diverting bore.

120. A method as claimed in any of Claims 74 to 119 in which the portion of the film formed on the non-bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the non-bridging portion thereof, each communicating opening in the non-bridging portion of the framework communicating with the diverting bore.

121. A method as claimed in Claim 119 or 120 in which in the expanded state of the framework the number of the communicating openings in the film formed on the bridging portion of the framework per unit surface area of the bridging portion of the film is less than the number of communicating openings in the film formed on the non-bridging portion of the framework per unit surface area of the non-bridging portion of the film.

122. A method as claimed in any of Claims 119 to 121 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 10% to 90% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

123. A method as claimed in any of Claims 119 to 122 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 15% to 50% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

124. A method as claimed in any of Claims 119 to 123 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 20% to 40% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

125. A method as claimed in any of Claims 119 to 124 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film is approximately 30% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

126. A method as claimed in any of Claims 119 to 125 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area less than the area of each communicating opening in the non-bridging portion of the film.

127. A method as claimed in any of Claims 119 to 126 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 5% to 90% of the area of each communicating opening in the non-bridging portion of the film.

128. A method as claimed in any of Claims 119 to 127 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 10% to 50% of the area of each communicating opening in the non-bridging portion of the film.

129. A method as claimed in any of Claims 119 to 128 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 20% to 40% of the area of each communicating opening in the non-bridging portion of the film.

130. A method as claimed in any of Claims 119 to 129 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area is approximately 30% of the area of each communicating opening in the non-bridging portion of the film.

131. A method as claimed in any of Claims 119 to 130 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.1 mm² to 1.2mm².

132. A method as claimed in any of Claims 119 to 131 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.2mm² to 1.1mm².

133. A method as claimed in any of Claims 119 to 132 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.25mm² to 0.99mm².

134. A method as claimed in any of Claims 119 to 133 in which the communicating openings in the non-bridging portion of the film are configured to supply adequate blood flow to one or both of branch vessels and perforators branching from the vessel when the stent is located in the vessel.

135. A method as claimed in any of Claims 74 to 134 in which the framework is of substantially cylindrical shape.

136. A method as claimed in any of Claims 74 to 135 in which the framework in the collapsed state is of substantially constant transverse cross-section along its longitudinal length.

137. A method as claimed in any of Claims 74 to 136 in which the framework in the expanded state is of substantially constant transverse cross-section along its longitudinal length.

138. A method as claimed in any of Claims 74 to 137 in which the outer diameter of the framework in the collapsed state lies in the range of 5% to 50% of the outer diameter of the framework in the expanded state.

139. A method as claimed in any of Claims 74 to 138 in which the outer diameter of the framework in the collapsed state lies in the range of 7.5% to 20% of the outer diameter of the framework in the expanded state.

140. A method as claimed in any of Claims 74 to 139 in which the outer diameter of the framework in the collapsed state is approximately 10% of the outer diameter of the framework in the expanded state.

141. A method as claimed in any of Claims 74 to 140 in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.5mm.

142. A method as claimed in any of Claims 74 to 141 in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.33mm.

143. A method as claimed in any of Claims 74 to 142 in which the outer diameter of the framework in the collapsed state is approximately 0.3mm.

144. A method as claimed in any of Claims 74 to 143 in which the outer diameter of the framework in the expanded state lies in the range of 1mm to 5mm.

145. A method as claimed in any of Claims 74 to 144 in which the outer diameter of the framework in the expanded state lies in the range of 2mm to 4mm.

146. A method as claimed in any of Claims 74 to 145 in which the outer diameter of the framework in the expanded state is approximately 3mm.

147. A method as claimed in any of Claims 74 to 146 in which the film extends over substantially the entire surface area of the framework on one or both of the outer surface and the inner surface thereof.

148. A method as claimed in any of Claims 74 to 147 in which the framework extends longitudinally between a first end and a second end thereof, and comprises a first non-bridging portion extending longitudinally from the first end to the bridging portion, and a second non-bridging portion extending longitudinally from the second end to the bridging portion.

149. A method as claimed in any of Claims 74 to 148 in which the bridging portion of the framework extends longitudinally between the first and second non-bridging portions thereof.

150. A method as claimed in any of Claims 74 to 149 in which the first and second non-bridging portions of the framework meet along a portion of the circumference of the framework, and together define the bridging portion.

151. A method for manufacturing a stent for use in one of the treatment and the alleviation of one of an aneurysm and a vessel wall deformity in an intracranial vessel, the method comprising forming an elongated tubular framework defining an outer circumferential surface and an elongated diverting bore extending longitudinally therethrough for diverting blood through the vessel past the one of the aneurysm and the vessel wall deformity, the framework defining a plurality of spaced apart interstices extending radially therethrough from the diverting bore to the outer surface of the framework, and forming a film on the framework on at least a bridging portion of the framework configured to bridge the one of the aneurysm and the vessel wall deformity when the stent is placed in the vessel, the portion of the film formed on the bridging portion of the framework being configured to restrict blood flow from the diverting bore to the one of the aneurysm and the vessel wall deformity.

152. A method as claimed in Claim 151 in which the portion of the film formed on the bridging portion of the framework comprises a non-porous film.

153. A method as claimed in Claim 151 in which the portion of the film formed on the bridging portion of the framework comprises a porous film.

154. A method as claimed in any of Claims 151 to 153 in which a portion of the film is formed on a non-bridging portion of the framework.

155. A method as claimed in Claim 154 in which the portion of the film formed on the non-bridging portion of the framework comprises non-porous film.

156. A method as claimed in Claim 154 in which the portion of the film formed on the non-bridging portion of the framework comprises a porous film.

157. A method as claimed in any of Claims 151 to 156 in which the framework is expandable from a collapsed state to an expanded state.

158. A method as claimed in any of Claims 151 to 157 in which the film is formed on the framework by coating the framework with a material in one of a liquid and powder form to form the film.

159. A method as claimed in any of Claims 151 to 158 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by spraying.

160. A method as claimed in any of Claims 151 to 159 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by sputtering.

161. A method as claimed in any of Claims 151 to 160 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by dipping the framework into the material in the one of the liquid and powder form to form the film.

162. A method as claimed in any of Claims 151 to 161 in which the material in the one of the liquid and powder form to form the film is coated onto the framework by an electro-static deposition process.

163. A method as claimed in any of Claims 151 to 162 in which the material in the one of the liquid and powder form to form the film is configured to extend across and close the interstices of the framework at least in the bridging portion thereof when coated onto the framework.

164. A method as claimed in any of Claims 151 to 163 in which the material in the one of the liquid and powder form to form the film is configured to extend across and close each of the interstices of the framework when coated onto the framework.

165. A method as claimed in any of Claims 151 to 164 in which the film is reinforced with a non- woven fabric.

166. A method as claimed in Claim 165 in which the non-woven fabric is applied to the framework by spinning.

167. A method as claimed in Claim 165 or 166 in which the non-woven fabric is applied to the framework by electrospinning.

168. A method as claimed in any of Claims 165 to 167 in which the non-woven fabric is applied to the framework prior to coating the framework with the film material.

169. A method as claimed in any of Claims 151 to 168 in which the material of the film comprises a biocompatible material.

170. A method as claimed in any of Claims 151 to 169 in which the material of the film comprises a polymeric material.

171. A method as claimed in any of Claims 151 to 170 in which the material of the film is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a nonpolymeric material, such as a hyperelastic thin film nitinol.

172. A method as claimed in any of Claims 151 to 171 in which the material of the film comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

173. A method as claimed in any of Claims 151 to 172 in which the film comprises one of a film, implanted at a molecular level with a medicament and a film coated with a medicament.

174. A method as claimed in Claim 173 in which the medicament comprises a medicament configured to reduce the thrombotic potential of the stent.

175. A method as claimed in Claim 173 or 174 in which the medicament comprises a medicament configured to minimise growth of atherosclerotic plaque.

176. A method as claimed in any of Claims 151 to 175 in which the material of the film comprises a biodegradable material.

177. A method as claimed in any of Claims 151 to 176 in which the film is formed on the framework when the framework is in the expanded state.

178. A method as claimed in any of Claims 151 to 177 in which the framework comprises a biocompatible material.

179. A method as claimed in any of Claims 151 to 178 in which the framework comprises a memory material.

180. A method as claimed in any of Claims 151 to 179 in which the framework comprises a metal alloy.

181. A method as claimed in any of Claims 151 to 180 in which the framework comprises one of an alloy of nickel and titanium, a cobalt alloy and stainless steel.

182. A method as claimed in any of Claims 151 to 181 in which the framework comprises a polymer material.

183. A method as claimed in any of Claims 151 to 182 in which the material of the framework is selected from one or more of the following materials, polyurethane, polytetrafluoroethylene, polyester, polyamide, polyolefin and a non-polymeric material, such as a hyperelastic thin film nitinol.

184. A method as claimed in any of Claims 151 to 183 in which the material of the framework comprises a polymeric material selected from one or more of poly(lactide-co-caprolactone) (PLCL), poly(caprolactone) (PCL), polylactides (PLA), poly(lactide-co-glycosides) (PLGA), polyacrylonitriles (PAN) and polyurethanes (PU).

185. A method as claimed in any of Claims 151 to 184 in which the framework comprises a biodegradable material.

186. A method as claimed in any of Claims 151 to 185 in which the material of the framework is one of implanted and coated with a medicament.

187. A method as claimed in Claim 186 in which the medicament comprises a medicament to reduce the thrombotic potential of the stent.

188. A method as claimed in Claim 186 or 187 in which the medicament comprises a medicament to minimise growth of atherosclerotic plaque.

189. A method as claimed in any of Claims 151 to 188 in which the framework is constructed from a tubular member, and the interstices are cut radially through the tubular member.

190. A method as claimed in Claim 189 in which the interstices are formed by laser cutting of the tubular member.

191. A method as claimed in Claim 189 or 190 in which the tubular member from which the framework is formed is selected to be of diameter substantially equal to the diameter of the framework in the expanded state thereof.

192. A method as claimed in any of Claims 151 to 191 in which the portion of the film formed on the bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the bridging portion thereof, each communicating opening communicating with the diverting bore.

193. A method as claimed in any of Claims 151 to 192 in which the portion of the film formed on the non-bridging portion of the framework comprises a plurality of spaced apart communicating openings extending therethrough adjacent at least some of the interstices of the framework in the non-bridging portion thereof, each communicating opening in the non-bridging portion of the framework communicating with the diverting bore.

194. A method as claimed in Claim 192 or 193 in which in the expanded state of the framework the number of the communicating openings in the film formed on the bridging portion of the framework per unit surface area of the bridging portion of the film is less than the number of communicating openings in the film formed on the non-bridging portion of the framework per unit surface area of the non-bridging portion of the film.

195. A method as claimed in any of Claims 192 to 194 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 10% to 90% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

196. A method as claimed in any of Claims 192 to 195 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 15% to 50% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

197. A method as claimed in any of Claims 192 to 196 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film lies in the range of 20% to 40% of the number of the communicating openings per unit surface area of the non-bridging portion of the film.

198. A method as claimed in any of Claims 192 to 197 in which in the expanded state of the framework the number of the communicating openings per unit surface area of the bridging portion of the film is approximately 30% of the number of the communicating openings per unit surface area of the nonbridging portion of the film.

199. A method as claimed in any of Claims 1922 to 198 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area less than the area of each communicating opening in the non-bridging portion of the film.

200. A method as claimed in any of Claims 192 to 199 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 5% to 90% of the area of each communicating opening in the non-bridging portion of the film.

201. A method as claimed in any of Claims 192 to 200 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 10% to 50% of the area of each communicating opening in the non-bridging portion of the film.

202. A method as claimed in any of Claims 192 to 201 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area lying in the range of 20% to 40% of the area of each communicating opening in the non-bridging portion of the film.

203. A method as claimed in any of Claims 192 to 202 in which in the expanded state of the framework each communicating opening in the bridging portion of the film is of area is approximately 30% of the area of each communicating opening in the non-bridging portion of the film.

204. A method as claimed in any of Claims 192 to 203 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.1 mm² to 1.2mm².

205. A method as claimed in any of Claims 192 to 204 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.2mm² to 1.1mm².

206. A method as claimed in any of Claims 192 to 205 in which in the expanded state of the framework the area of each communicating opening in the film is of area in the range of 0.25mm² to 0.99mm².

207. A method as claimed in any of Claims 192 to 206 in which the communicating openings in the non-bridging portion of the film are configured to supply adequate blood flow to one or both of branch vessels and perforators branching from the vessel when the stent is located in the vessel.

208. A method as claimed in any of Claims 151 to 207 in which the framework is of substantially cylindrical shape.

209. A method as claimed in any of Claims 151 to 208 in which the framework in the collapsed state is of substantially constant transverse cross-section along its longitudinal length.

210. A method as claimed in any of Claims 151 to 209 in which the framework in the expanded state is of substantially constant transverse cross-section along its longitudinal length.

211. A method as claimed in any of Claims 151 to 210 in which the outer diameter of the framework in the collapsed state lies in the range of 5% to 50% of the outer diameter of the framework in the expanded state.

212. A method as claimed in any of Claims 151 to 211 in which the outer diameter of the framework in the collapsed state lies in the range of 7.5% to 20% of the outer diameter of the framework in the expanded state.

213. A method as claimed in any of Claims 151 to 212 in which the outer diameter of the framework in the collapsed state is approximately 10% of the outer diameter of the framework in the expanded state.

214. A method as claimed in any of Claims 151 to 213 in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.5mm.

215. A method as claimed in any of Claims 151 to 214 in which the outer diameter of the framework in the collapsed state lies in the range of 0.25mm to 0.33mm.

216. A method as claimed in any of Claims 151 to 215 in which the outer diameter of the framework in the collapsed state is approximately 0.3mm.

217. A method as claimed in any of Claims 151 to 216 in which the outer diameter of the framework in the expanded state lies in the range of 1mm to 5mm.

218. A method as claimed in any of Claims 151 to 217 in which the outer diameter of the framework in the expanded state lies in the range of 2mm to 4mm.

219. A method as claimed in any of Claims 151 to 218 in which the outer diameter of the framework in the expanded state is approximately 3mm.

220. A method as claimed in any of Claims 151 to 219 in which the film extends over substantially the entire surface area of the framework on one or both of the outer surface and the inner surface thereof.

221. A method as claimed in any of Claims 151 to 220 in which the framework extends longitudinally between a first end and a second end thereof, and comprises a first non-bridging portion extending longitudinally from the first end to the bridging portion, and a second non-bridging portion extending longitudinally from the second end to the bridging portion.

222. A method as claimed in any of Claims 151 to 221 in which the bridging portion of the framework extends longitudinally between the first and second non-bridging portions thereof.

223. A method as claimed in any of Claims 151 to 222 in which the first and second non-bridging portions of the framework meet along a portion of the circumference of the framework, and together define the bridging portion.