WO1994000088A1 - Curved electrode array - Google Patents
Curved electrode array Download PDFInfo
- Publication number
- WO1994000088A1 WO1994000088A1 PCT/AU1993/000291 AU9300291W WO9400088A1 WO 1994000088 A1 WO1994000088 A1 WO 1994000088A1 AU 9300291 W AU9300291 W AU 9300291W WO 9400088 A1 WO9400088 A1 WO 9400088A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- array
- electrode array
- curved
- curved portion
- intracochlear
- Prior art date
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/02—Details
- A61N1/04—Electrodes
- A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
- A61N1/0526—Head electrodes
- A61N1/0541—Cochlear electrodes
Definitions
- the present invention relates to an implantable electrode array for intracochlear implantation.
- One difficulty relates to insertion.
- the electrode array is fully inserted to a depth of 1 1/2 turns of the scala tympani.
- the average insertion depth is, however, rather less than one full turn. This inhibits the ability of the array to stimulate those parts of the auditory neurons responsible for lower frequency sounds, and as a result induced hearing sensations may be limited to the higher frequency regions only.
- intracochlear electrode arrays A further problem with known intracochlear electrode arrays is that they often do not locate in the optimal position for stimulation.
- a straight electrode array ends to engage the outer wall of the scala tympani.
- optimal stimulation is obtained from locating the electrodes adjacent to the inner wall, near the modiolus.
- a spiral-shaped intracochlear electrode array has been developed by the University of California at San Francisco (UCSF). This device, however, is relatively thick, occupying almost all the scala tympani, thereby limiting the depth of insertion. Further, it is a "sided" device, whereby the electrodes are presented only on the inner and upper surfaces of the array and left and right electrode arrays are distinct. The limited surface area of the electrodes may result in higher charge densities, and contribute to tissue damage. It is an object of the present invention to provide an electrode array which at least ameliorates the disadvantages of the prior art. Summary of the Invention
- the present invention provides an electrode array having a terminal curved portion, and a straight portion, the curved portion having substantially the shape of a exponential curve with between 1 and 2 turns.
- the device tapers towards the tip.
- the tip of the array is somewhat less curved to facilitate easier insertion.
- the array is formed so as to be resilient and have memory, so that once straightened and released it assumes its predetermined shape.
- the array is formed from a silicone polymer such as Silastic MDX 4-4210, and the platinum lead wires have a diameter of about 25 ⁇ m and are formed from a platinum alloy having about 20% to about 30% iridium.
- the electrodes are formed from platinum bands, selected such that the bands will fit freely within the scala tympani, and the surface area of the bands is large enough to prevent the production of high charge densities in use.
- Figure 1 illustrates one form of the inventive electrode array
- Figure 2 illustrates an insertion tool adapted for use with the inventive array.
- Figure 1 relates to one form of the present invention using band electrodes and being generally similar in construction to the
- Cochlear Fry. Ltd. 22 channel device which is commercially available.
- the present invention relates solely to the construction, dimensions and mechanical properties exhibited by intra-cochlear electrode arrays.
- the inventors In order to produce an array which was shaped so as to properly engage the desired portions of the scala tympani while maximising insertion depth and minimising trauma, the inventors have more accurately defined the shape of the inner wall of the scala tympani.
- the inventors made a number of moulds of human cochlear scala tympani from cadavers, characterised the shape relative to the central axis, and derived a mathematical expression to provide a best fit for the experimental data.
- the object was to provide a curved array which would be suitable for most patients in terms of minimising trauma, maximising insertion depth, and locating the array adjacent to the modiolus.
- Array 10 comprises an optional angled portion 21 , a straight portion 16 including electrodes 12, and a curved portion 18 also including electrodes 12 which in general forms a spiral about axis 14.
- the tip region 20, containing about the last 2 bands before the tip does not conform to the exponential curve, as this would be a very tight curve for the electrode array to pass the basal turn and difficult to insert. It is instead only slightly curved.
- the illustrated array is tapered towards the tip.
- Preferred dimensions are about 0.6 mm at the outer end of straight portion16 and about 0.4 mm at the tip 20. This facilitates deep insertion while minimising trauma to the various structures.
- the array It is important that the array have a structure which is flexible, to minimise insertion trauma, yet resilient so that the correct shape is resumed after the insertion procedure. There is very little advantage in carefully characterising the shape of the array unless this is maintained after insertion.
- wires which are provided to electrically connect the electrodes. It is preferred according to the present invention that these be formed from a resilient material rather than 90% platinum
- iridium alloy wire 10% iridium alloy wire.
- One suitable material is an alloy of platinum with 20 to
- the wires may be annealed.
- a further aspect of the present invention relates to the method of insertion.
- inventive array may be inserted using any suitable technique.
- Such a tool may comprise a teflon tube 32 with a slit
- Array 10 In use, the curved 18 and straight 16 portions of the array 10 are inserted into tube 32 such that the curve of the array 10 is directed away from the slit 33.
- Array 10 includes flange 22, which in use is engaged by the rod 31 so as to move the electrode array 10 out from the end of the insertion tool. It will be understood that the angled portion 21 of array 1O protrudes from slit 33 in the tube 32.
- the array 10 is placed within tube 32, and the tube 32 inserted into the straight portion of the basal turn of the scala tympani - typically about 8 mm from the round window.
- the rod is then moved forward, the array is thus inserted directly into the curved portion of the scala tympani in its predetermined curved shape, until the rod is nearly at the end of the tube and the array is freed.
- the tool may be a suitably modified syringe and catheter.
- a flange or mark may be provided so as to indicate to a surgeon the appropriate insertion depth for the tool. It will be noted that the present invention, although curved, is not sided: i.e., one device may be manufactured and inserted into either the left or right cochlea.
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- Health & Medical Sciences (AREA)
- Otolaryngology (AREA)
- Cardiology (AREA)
- Heart & Thoracic Surgery (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Radiology & Medical Imaging (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Electrotherapy Devices (AREA)
Abstract
An electrode array (10) for intracochlear insertion, having a terminal curved portion (18) and a straight portion (16), the curved portion having between one and two turns. Optionally included are an angled portion (21) and a flange (22) to facilitate insertion.
Description
CURVED ELECTRODE ARRAY
Field of invention
The present invention relates to an implantable electrode array for intracochlear implantation. Background Art
Known cochlear implant devices require several improvements in order to overcome certain deficiencies of a mechanical or structural nature.
One difficulty relates to insertion. Ideally, and in the best surgical results, the electrode array is fully inserted to a depth of 1 1/2 turns of the scala tympani. The average insertion depth is, however, rather less than one full turn. This inhibits the ability of the array to stimulate those parts of the auditory neurons responsible for lower frequency sounds, and as a result induced hearing sensations may be limited to the higher frequency regions only.
A further problem with known intracochlear electrode arrays is that they often do not locate in the optimal position for stimulation. During the surgical insertion procedure a straight electrode array :ends to engage the outer wall of the scala tympani. However, optimal stimulation is obtained from locating the electrodes adjacent to the inner wall, near the modiolus.
Another consideration is the minimisation of trauma to the cochlea. Straight electrode arrays tend to distort the spiral ligament, basilar membrane or other structures during insertion, possibly causing trauma and creating insertion difficulties.
A spiral-shaped intracochlear electrode array has been developed by the University of California at San Francisco (UCSF). This device, however, is relatively thick, occupying almost all the scala tympani, thereby limiting the depth of insertion. Further, it is a "sided" device, whereby the electrodes are presented only on the inner and upper surfaces of the array and left and right electrode arrays are distinct. The limited surface area of the electrodes may result in higher charge densities, and contribute to tissue damage. It is an object of the present invention to provide an electrode array which at least ameliorates the disadvantages of the prior art.
Summary of the Invention
The present invention provides an electrode array having a terminal curved portion, and a straight portion, the curved portion having substantially the shape of a exponential curve with between 1 and 2 turns. Preferably, the device tapers towards the tip. Preferably, the tip of the array is somewhat less curved to facilitate easier insertion. Preferably the array is formed so as to be resilient and have memory, so that once straightened and released it assumes its predetermined shape. Preferably, the curved part of the array describes about one and one quarter turns with its axis corresponding to the function R (θ) = AeB(β+ c ), wherein A is in the range of about 120 μm to about 144 μm, and B is about 0.2, and C is 7π/6.
Preferably, the array is formed from a silicone polymer such as Silastic MDX 4-4210, and the platinum lead wires have a diameter of about 25 μm and are formed from a platinum alloy having about 20% to about 30% iridium. Preferably the electrodes are formed from platinum bands, selected such that the bands will fit freely within the scala tympani, and the surface area of the bands is large enough to prevent the production of high charge densities in use. Brief Description of Drawings
One embodiment of the invention will be described with reference to the drawings, in which:
Figure 1 illustrates one form of the inventive electrode array; and - Figure 2 illustrates an insertion tool adapted for use with the inventive array.
Detailed Description A preferred embodiment of the invention will now be described. It is emphasised that this is illustrative and not intended to be limitative.
The embodiment of Figure 1 relates to one form of the present invention using band electrodes and being generally similar in construction to the
Cochlear Fry. Ltd. 22 channel device which is commercially available. The present invention relates solely to the construction, dimensions and mechanical properties exhibited by intra-cochlear electrode arrays.
In order to produce an array which was shaped so as to properly engage the desired portions of the scala tympani while maximising insertion depth and minimising trauma, the inventors have more accurately defined the shape of the inner wall of the scala tympani. The inventors made a number of moulds of human cochlear scala tympani from cadavers, characterised the shape relative to the central axis, and derived a mathematical expression to provide a best fit for the experimental data. The object was to provide a curved array which would be suitable for most patients in terms of minimising trauma, maximising insertion depth, and locating the array adjacent to the modiolus.
The following expression for the optimal shape of the longitudinal axis of the implant was obtained:
- R(θ) = AeB(β+ c ), where R(μm = radial distance of the inner wall from the central axis of the scala tympani, θ = angle about this axis( 0< θ< 5π/2 ) and A, B and C are values obtained from experimental data. It has been observed that A has a mean value of 132 with a standard deviation of 8, B is consistently 0.2, and C is set as 7π/6 . It is accordingly preferred that B is about 0.2 and A is in the range of 116 to 148, preferably about 132.
Referring to Figure 1 , the preferred shape is illustrated. Array 10 comprises an optional angled portion 21 , a straight portion 16 including electrodes 12, and a curved portion 18 also including electrodes 12 which in general forms a spiral about axis 14.
It is noted that the tip region 20, containing about the last 2 bands before the tip, does not conform to the exponential curve, as this would be a very tight curve for the electrode array to pass the basal turn and difficult to insert. It is instead only slightly curved.
The illustrated array is tapered towards the tip. Preferred dimensions are about 0.6 mm at the outer end of straight portion16 and about 0.4 mm at the tip 20. This facilitates deep insertion while minimising trauma to the various structures.
It is important that the array have a structure which is flexible, to minimise insertion trauma, yet resilient so that the correct shape is resumed after the
insertion procedure. There is very little advantage in carefully characterising the shape of the array unless this is maintained after insertion.
One way to achieve this is to use the wires which are provided to electrically connect the electrodes. It is preferred according to the present invention that these be formed from a resilient material rather than 90% platinum
10% iridium alloy wire. One suitable material is an alloy of platinum with 20 to
30% iridium. The wires may be annealed.
A further aspect of the present invention relates to the method of insertion.
It will be appreciated that the inventive array may be inserted using any suitable technique.
One such method proposed according to the present invention involves the use of a suitable insertion tool. It will be understood that the diagram is somewhat exaggerated laterally so as to more clearly illustrate the operation of the tool. Referring to figure 2 .such a tool may comprise a teflon tube 32 with a slit
33 provided longitudinally, and a rod 31 within the tube 32 enabled to be moved longitudinally by depressing plunger 30.
In use, the curved 18 and straight 16 portions of the array 10 are inserted into tube 32 such that the curve of the array 10 is directed away from the slit 33. Array 10 includes flange 22, which in use is engaged by the rod 31 so as to move the electrode array 10 out from the end of the insertion tool. It will be understood that the angled portion 21 of array 1O protrudes from slit 33 in the tube 32.
Hn use, the array 10 is placed within tube 32, and the tube 32 inserted into the straight portion of the basal turn of the scala tympani - typically about 8 mm from the round window. The rod is then moved forward, the array is thus inserted directly into the curved portion of the scala tympani in its predetermined curved shape, until the rod is nearly at the end of the tube and the array is freed.
The tool may be a suitably modified syringe and catheter. A flange or mark may be provided so as to indicate to a surgeon the appropriate insertion depth for the tool.
It will be noted that the present invention, although curved, is not sided: i.e., one device may be manufactured and inserted into either the left or right cochlea.
It will be understood that modifications and variations are possible within the general scope of the present invention.
Claims
1 . An electrode array for intracochlear insertion having a terminal curved portion, and a straight portion, the curved portion having between 1 and 2 turns.
2. An electrode array for intracochlear insertion having a terminal curved portion, and a straight portion, the curved portion having a central axis conforming substantially to
R(θ) = AeB(θ+C), where R = radial distance of the inner wall from the central axis of the scala tympani, θ = angle about this axis( 0< θ< 5π/2 ) and A, B and C are constants , A in the range of 116 to 148, B is about 0.2, and C is about 7π/6 .
3. An electrode array according to claim 1 , wherein the array is formed so as to be resilient and have memory, so that once straightened and released it assumes its predetermined shape.
4. An electrode array according to claim 1 , wherein the tip of the array is somewhat less curved to facilitate easier insertion.
5. An electrode array according to claim 1 , wherein the array includes an optional angled portion and a flange so as to facilitate insertion.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU42980/93A AU4298093A (en) | 1992-06-22 | 1993-06-17 | Curved electrode array |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPL3078 | 1992-06-22 | ||
AUPL307892 | 1992-06-22 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994000088A1 true WO1994000088A1 (en) | 1994-01-06 |
Family
ID=3776235
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU1993/000291 WO1994000088A1 (en) | 1992-06-22 | 1993-06-17 | Curved electrode array |
Country Status (1)
Country | Link |
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WO (1) | WO1994000088A1 (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5630839A (en) * | 1991-10-22 | 1997-05-20 | Pi Medical Corporation | Multi-electrode cochlear implant and method of manufacturing the same |
WO1997033647A1 (en) * | 1996-03-13 | 1997-09-18 | Med-El Elektromedizinische Geräte GmbH | Device and method for implants in ossified cochleas |
US5800500A (en) * | 1995-08-18 | 1998-09-01 | Pi Medical Corporation | Cochlear implant with shape memory material and method for implanting the same |
EP0861570A1 (en) * | 1995-11-13 | 1998-09-02 | Cochlear Limited | Implantable microphone for cochlear implants and the like |
WO1998040119A1 (en) * | 1997-03-10 | 1998-09-17 | Med-El Elektromedizinische Geräte GmbH | Apparatus and method for perimodiolar cochlear implant with retro-positioning |
WO2001012115A1 (en) * | 1999-08-18 | 2001-02-22 | Epic Biosonics Inc. | Modiolar hugging electrode array |
CN104644330A (en) * | 2013-11-20 | 2015-05-27 | 上海力声特医学科技有限公司 | Artificial cochlear electrode |
US11690548B2 (en) | 2007-10-17 | 2023-07-04 | Neuronexus Technologies, Inc. | Method for implanting an implantable device in body tissue |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU5172085A (en) * | 1985-01-17 | 1986-07-24 | Erwin S. Hochmair | Auditory stimulating system |
AU7322787A (en) * | 1983-04-11 | 1987-09-10 | Commonwealth Of Australia, The | Implant prosthesis current switching and power supply |
US4819647A (en) * | 1984-05-03 | 1989-04-11 | The Regents Of The University Of California | Intracochlear electrode array |
-
1993
- 1993-06-17 WO PCT/AU1993/000291 patent/WO1994000088A1/en active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU7322787A (en) * | 1983-04-11 | 1987-09-10 | Commonwealth Of Australia, The | Implant prosthesis current switching and power supply |
US4819647A (en) * | 1984-05-03 | 1989-04-11 | The Regents Of The University Of California | Intracochlear electrode array |
AU5172085A (en) * | 1985-01-17 | 1986-07-24 | Erwin S. Hochmair | Auditory stimulating system |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5630839A (en) * | 1991-10-22 | 1997-05-20 | Pi Medical Corporation | Multi-electrode cochlear implant and method of manufacturing the same |
US5800500A (en) * | 1995-08-18 | 1998-09-01 | Pi Medical Corporation | Cochlear implant with shape memory material and method for implanting the same |
EP0861570A1 (en) * | 1995-11-13 | 1998-09-02 | Cochlear Limited | Implantable microphone for cochlear implants and the like |
EP0861570A4 (en) * | 1995-11-13 | 2000-02-02 | Cochlear Ltd | Implantable microphone for cochlear implants and the like |
WO1997033647A1 (en) * | 1996-03-13 | 1997-09-18 | Med-El Elektromedizinische Geräte GmbH | Device and method for implants in ossified cochleas |
US5922017A (en) * | 1996-03-13 | 1999-07-13 | Med-El Elektromedizinische Gerate Gmbh | Device and method for implants in ossified cochleas |
WO1998040119A1 (en) * | 1997-03-10 | 1998-09-17 | Med-El Elektromedizinische Geräte GmbH | Apparatus and method for perimodiolar cochlear implant with retro-positioning |
US5999859A (en) * | 1997-03-10 | 1999-12-07 | Med-El- Elektromedizinische Gerate G.M.B.H. | Apparatus and method for perimodiolar cochlear implant with retro-positioning |
WO2001012115A1 (en) * | 1999-08-18 | 2001-02-22 | Epic Biosonics Inc. | Modiolar hugging electrode array |
US11690548B2 (en) | 2007-10-17 | 2023-07-04 | Neuronexus Technologies, Inc. | Method for implanting an implantable device in body tissue |
CN104644330A (en) * | 2013-11-20 | 2015-05-27 | 上海力声特医学科技有限公司 | Artificial cochlear electrode |
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