EP4731296A1 - Medical electrode device for implantation into a patient and method for fabricating a medical electrode device - Google Patents

Abstract

A medical electrode device (1) for implantation into a patient (P) comprises a lead body (10) extending longitudinally along a longitudinal axis (L), at least one electrical line (13) extending within the lead body (10), and a flattened electrode end (11) arranged at a distal end of the lead body (10) and comprising a carrier body (14) and at least one primary electrical contact element (12) connected to the at least one electrical line (13). The at least one primary electrical contact element (12) is arranged on a primary face (142) of the carrier body (14) and configured to contact tissue in proximity to the flattened electrode end (11) in an implanted state of the medical electrode device (1). At least a portion of the carrier body (14) is made from a material composition comprising an electrically insulating first material in which particles (15) of an additive second material different than the first material are dispersed.

Description

Medical electrode device for implantation into a patient and method for fabricating a medical electrode device

TECHNICAL FIELD

The present invention relates to a medical electrode device for implantation into a patient and a method for fabricating a medical electrode device.

BACKGROUND

A medical electrode device of the type concerned herein may for example serve for neurostimulation and for this may be implanted into a patient for example in the region of the spinal cord, for example into the epidural space near the spinal cord of the spinal column of a patient. In this way a nerve stimulation at the spinal cord may be achieved by injecting electrical stimulation currents.

An electrode device of the kind concerned herein however may also be used for emitting stimulation signals or receiving sense signals at other locations within a patient, for example within the brain or in cardiac applications.

An electrode device of the kind concerned herein comprises at least one lead body, preferably two lead bodies extending along a longitudinal axis and having a proximal end and a distal end. One or multiple electrical lines extend within the lead body. A flattened electrode end is arranged at the distal end of the lead body and comprises a carrier body and an arrangement of contact elements arranged on a primary face of the carrier body for contacting tissue. The electrical contact elements are electrically connected to the one or the multiple electrical lines extending within the lead body. In an implanted state, the lead body with its proximal end is connected to a generator for generating stimulation signals. The flattened electrode end is implanted in a patient, for example in the epidural space of the spinal column, such that the contact elements of the electrode end are in contact with surrounding tissue and may be used to inject stimulation signals into the tissue in order to provide for a stimulation action in the vicinity e.g. of the spinal cord.

The medical electrode device for example has the shape of a so-called paddle electrode, the flattened electrode end having a paddle-like shape carrying e.g., at least electrical contact element, particularly an arrangement of multiple evenly or unevenly spaced contact elements, on its surface for emission of electrical signals into and/or reception of electrical signals from surrounding tissue.

Different designs of paddle electrodes are known, for example, from US 6,895,283, US 2008/0046050 Al, US 2014/0172057 Al and US 9,561,363.

Generally, a medical electrode device of the kind concerned herein shall be non-hazardous to the patient in MRI environments, i.e., causing no adverse effects during exposure to magnetic and electromagnetic fields of an MRI machine, also called MRI conditional. A patient in which an implant system comprising a medical electrode device is implanted may have to undergo an MRI examination, such that it must be made sure that the patient is not posed with a hazardous risk due to the interaction of the implanted system with the MRI device.

Generally, electrical fields produced by an MRI device may couple into the electrode device, wherein the electrode device with the at least one electrical line extending within the lead body and the flattened electrode end arranged at the distal end of the lead body may exhibit antenna or a resonant behavior, causing a coupling of the RF excitation field of the MRI device into the electrode device and resulting in an increase of the electrical field strength in the vicinity of the electrode device. This makes it necessary to design the electrode device such that in particular in the region of the flattened electrode end, at which the electrical

21.151P-WO 17.05.2024 contact elements shall come into electric contact with surrounding tissue, an excessive heating is prevented.

DE 10 2020 100 121 Al discloses an implantable electrode comprising an outer tube having a distal end and a proximal end. At the proximal end the electrode is connectable to an active device. Within the outer tube at least one electrical line is arranged. In the region of the distal end in addition an electrical electrode pole is formed for electrically contacting with tissue in an implanted state of the electrode. In the region of the distal end, herein, an electrical tap line is formed in connection with the electrical line of the electrode such that the electrical length of the electrical line is modified.

US 2014/0135614 Al discloses an implantable electrical stimulation lead including a lead body having a distal end, a proximal end, and a longitudinal length. A plurality of electrodes is disposed along the distal end of the lead body. A plurality of terminals is disposed along the proximal end of the lead body. A plurality of conductors electrically couples the plurality of electrodes to the plurality of terminals. To reduce or redistribute current induced in the conductors during an MRI procedure, an internal conductive structure, such as a dummy coil or hollow metal tube, may be provided.

US 2005/0222647 Al discloses a pulse stimulation system configured for implantation into a patient’s body, comprising a pulse stimulator, a conductive stimulation lead having a proximal end electrically coupled to the pulse stimulator and having a distal end, and an electrode assembly coupled to the distal end of the stimulation lead. The electrode assembly comprises an electrode body having a therapy electrode thereon that is electrically coupled to the stimulation lead for delivering therapy to the patient. A floating electrode is configured to contact the patient’s body tissue and has a surface area substantially larger than that of the therapy electrode.

SUMMARY

It is an object of the instant invention to provide a medical electrode device and a method for fabricating a medical electrode device which allow for a reduced risk of an excessive

21.151P-WO 17.05.2024 heating in particular in the vicinity of the flattened electrode end due to RF excitation fields during an MRI examination, while allowing for an easy and cost-efficient production of the electrode device.

In one aspect, a medical electrode device for implantation into a patient comprises a lead body extending longitudinally along a longitudinal axis. At least one electrical line extends within the lead body. A flattened electrode end is arranged at a distal end of the lead body and comprises a carrier body and at least one primary electrical contact element connected to the at least one electrical line, wherein the at least one primary electrical contact element is arranged on a primary face of the carrier body and configured to contact tissue in proximity to the flattened electrode end in an implanted state of the medical electrode device. At least a portion of the carrier body is made from an electrically insulating first material in which particles of an additive second material different than the first material are dispersed. According to an embodiment, the size of said particles is chosen according to the additive second material. For instance, for using silicon dioxide as additive second material, particle size can be chosen less than or equal to 50 nm.

The medical electrode device for example may form a so-called paddle electrode which may be used for example for a neuro-stimulation device. The medical electrode device in particular may be designed for connection to an active device at its proximal end, the active device serving as a stimulation device for generating electrical stimulation signals which, via the at least one electrical line, are provided to the at least one electrical contact element on the flattened electrode end for causing an electrical stimulation in the region of the flattened electrode end.

Accordingly, the at least one electrical contact element is particularly configured to transmit therapeutic electrical pulses to the tissue of a patient and/or to sense physiological electric tissue form the tissue of a patient.

According to an embodiment, the flattened electrode end comprises a multiplicity of electrical contact elements and a multiplicity of electrical line, wherein one electrical contact elements of the multiplicity of electrical contact elements is connected to one electrical line

21.151P-WO 17.05.2024 of the multiplicity of electrical lines, respectively. In one embodiment, the flattened electrode end comprises 8 to 16 electrical contact elements and 8 to 16 electrical lines, wherein one electrical contact elements is connected to one electrical line, respectively. Particularly, the number of electric contact elements of the multiplicity of electrical contact elements is consistent with number of electrical lines of the multiplicity of electrical lines.

The flattened electrode end, in an implanted state, rests within tissue of a patient, for example in the region of the spinal cord, for example in the epidural space near the spinal cord of the spinal column of the patient, in order to allow a nerve stimulation at the spinal cord by injecting electrical stimulation currents via the arrangement of electrical contact elements on the flattened electrode end.

The at least one electrical line or the multiplicity of electrical lines extending within the lead body together with the at least one electrical contact element or the multiplicity of electrical contact elements arranged on the flattened electrode end forms an electrical structure, which may be resonant at RF frequencies used within an MRI examination. For example, during an MRI examination using an MRI device at a magnetic field strength of 1.5 Tesla, an RF excitation field is produced at the so-called Lamor frequency of 63,87 MHz. At an MRI magnetic field strength of 3 Tesla, the RF excitation field is at a frequency of 127.74 MHz. If the electrical structure formed by the at least one electrical line extending along the lead body and the electrical contact elements arranged on the flattened electrode end is at or close to a resonance at the RF excitation frequency, the excitation field may couple into the electrical structure and may cause a substantial field increase in the region of the electrode device. Because the at least one or the multiple primary electrical contact elements are designed to contact, in an implanted state, with tissue in the vicinity of the flattened electrode end, the field increase on the electrode device may cause a heating of tissue in particular at the locations of the at least one or multiple primary electrical contact elements, which however shall be prevented.

The carrier body of the flattened electrode end commonly is made of an electrically insulating material, such that the alt least one primary electrical contact element or the multiplicity of electrical contact elements of the electrode end are electrically insulated from

21.151P-WO 17.05.2024 one another at the excitation frequencies used for providing for a therapeutic stimulation by means of the electrode device, for example at frequencies below 10 MHz, in particular below 1 MHz. The different electrical contact elements for example are particularly connected to different electrical lines running along and within the lead body, such that distinguished signals may be fed into the contact elements for injection into the patient for achieving a therapeutic action.

In order to prevent an excessive heating in particular at the locations of the at least one or multiple primary electrical contact elements, it herein is proposed to use a material composition for fabricating the carrier body which comprises an electrically insulating first material in which particles of an additive second material different than the first material are dispersed. The first material provides e.g., for a base material of the carrier body and is an electrically insulating material, for example a plastics material, such as a polymer material, for example a polyurethane material or a silicone material. In the first material particles of an additive second material are embedded, the particles of the second material serving to modify the material characteristics of the first material in order to alter the dielectric property of the carrier body.

In particular, by means of the additive second material dispersed in the insulating first material it may be achieved that RF energy as received during an MRI examination in an MRI device, for example at a frequency of 63,87 MHz (corresponding to a 1.5 Tesla MRI device) or 127.74 MHz (corresponding to a 3 Tesla MRI device), is dissipated over a broader volume, such that an excessive heating at the locations of the electrical contact elements on the primary face of the carrier body is prevented. In particular, by modifying the material characteristics of the material of the carrier body it may be achieved that RF energy coupled into the electrode device during an MRI examination is dissipated over the entire volume of the carrier body resting within tissue and its surrounding outer faces. As energy dissipation hence is not limited to the interfaces of the at least one or multiple primary therapeutic electrical contact elements, a heating effect in the surrounding of the electrode device is reduced, such that a localized excessive heating at particular locations is prevented.

21.151P-WO 17.05.2024 In one embodiment, the additive second material is characterized by a higher electrical conductivity than the first material. By adding particles of the additive second material to the first material, hence, the conductive characteristics of the carrier body are modified. The amount of particles added to the material composition herein generally is such that the insulating characteristics of the carrier body in the range of the stimulation frequencies are not significantly altered, but the carrier body maintains its insulative characteristics for insulating the therapeutic contact elements at the primary face of the flattened electrode end, wherein at increased MRI frequencies, e.g. 63,87 MHz (corresponding to a 1.5 Tesla MRI device) or 127.74 MHz (corresponding to a 3 Tesla MRI device), the conductivity of the carrier body is increased by the added conductive particles. This causes a dissipation of RF energy at an increased MRI frequency over the volume of the carrier body, as RF energy at the increased MRI frequency is conductively spread over the volume of the carrier body.

In this embodiment, the additive second material may for example essentially consist of comprise a conductive carbon material, such as a graphite material. In particular, the additive second material may comprise a conductive carbon compound, for example a tungsten carbon compound, e.g., tungsten carbide. Alternatively, the additive second material essentially consists or comprises a metal, e.g., tungsten or titanium. Preferably, the additive second material is electrically conductive and biocompatible. By adding the additive second material, the electrical conductivity characteristics of the carrier body is not increased such that the low frequency therapeutic signal is impacted. In particular, the volume and evenness of dispersion of the additive second material in the insulating first material are control parameters.

In one embodiment, the additive second material may be characterized by a higher permittivity than the first material. By adding the particles of the additive second material to the material composition, hence, the permittivity of the carrier body may be modified, and hence in particular the capacitive characteristics of the carrier body may be influenced. This makes use of the fact that the electrode device in an implanted state with its flattened electrode end rests within tissue, the tissue being generally conductive. The insulative carrier body herein exhibits a generally capacitive behavior, capacitive electrodes being formed at either side of the flattened electrode end by the surrounding tissue. By increasing the

21.151P-WO 17.05.2024 permittivity of the carrier body by adding particles of a material having an increased permittivity, hence, the capacitance of the structure may be increased.

In this embodiment, the additive second material may for example essentially consist or comprise a dielectric ceramic material, particularly barium titanate and/or titanium dioxide.

As the capacitive reactance is inversely proportional to the frequency, an increase of capacitance by adding particles of an additive material having an increased conductivity and/or permittivity may affect the dissipation of RF energy at an increased MRI frequency, but beneficially does not influence therapeutic excitation signals at a stimulation frequency substantially lower than the MRI frequency. At a low therapeutic stimulation frequency, the capacitive reactance across the carrier body generally is large, such that the emission of the stimulation signals via the contact elements is not substantially influenced. At the increased MRI frequency, in contrast, the capacitive reactance is significantly reduced, such that RF energy coupled into the flattened electrode end at the MRI excitation frequency may substantially be confined to the carrier body and substantially only fringe fields are emitted into the surrounding tissue. This may lead to a lower tissue SAR and hence a lower power deposition.

Heat in addition is removed from the flattened electrode end via the at least one electrical line, which is preferably made from a metallic wire having a high thermal conductivity, causing the flattened electrode end to quickly reach a thermal equilibrium at a relatively low temperature.

In one embodiment, the material composition comprises an amount of the additive second material in the range between 10 and 70 mass-%. The remainder of the material composition in particular may consist of the insulating first material, wherein it also is conceivable that further material components different than the first material and the second material are added to the composition.

In one embodiment, the flattened electrode end comprises at least one secondary contact element arranged on a secondary face of the carrier body facing away from the primary face.

21.151P-WO 17.05.2024 The carrier body forming a carrier for the flattened electrode end assumes a generally flat shape, the at least one primary or the multiple primary electrical contact elements for emitting electrical stimulation signals into tissue being arranged on a primary face of the carrier body. In addition, in one embodiment, one or multiple secondary contact elements are arranged on the opposite, secondary face, the secondary contact elements functioning as parasitic electrode elements which do not serve to emit stimulation signals during operation of the electrode device, but rather affect the capacitive structure of the flattened electrode end at an increased MRI frequency.

The at least one secondary contact element beneficially is not electrically connected to the at least one electrical line and hence is not fed with stimulation signals during operation of the electrode device. The at least one secondary contact element, in one embodiment, is not connected to any other conductive structure of the electrode device, in particular an electrical connection line in connection with an active device to which the electrode device is connected. According to an embodiment, the secondary contact element has a rectangular shape. According to other embodiments, the secondary contact element has a shape of a circle, cross, ring, mesh, coil, or the like.

By means of a secondary contact element at the opposite, secondary face of the carrier body, energy may be dissipated at the secondary face of the carrier body, while not adversely affecting the emission of stimulation signals via the at least one primary or multiple primary contact elements at the primary face of the carrier body. The secondary contact elements may be configured to come into contact with tissue or, in another embodiment, may be embedded within the material of the carrier body such that they do not come into electrical contact with surrounding tissue in an implanted state of the medical electrode device. For example, the at least one secondary contact element may be coated with an insulating material such that the at least one secondary contact element is capacitively coupled to the outside and hence is electrically insulated towards surrounding tissue.

In one embodiment, the carrier body comprises at least one spatial region made from the material composition. Other regions of the carrier body herein may be made from another material composition, such that the material composition comprising the insulating first

21.151P-WO 17.05.2024 material and particles of the additive second material is used to form only certain regions of the carrier body. By means of such regions, for example portions of the carrier body may be formed to exhibit an increased conductivity and/or permittivity, such that structures for improved dissipation of RF energy over the volume of the carrier body may be established.

In one embodiment, the at least one spatial region is spatially distant, along a direction perpendicular to the primary face, from the primary face. Whereas the electrical contact elements for emitting electrical stimulation signals are arranged on the primary face, the spatial regions formed from the material composition comprising the insulating first material and the dispersed particles of the additive second material are distant to the primary face, in particular towards the secondary face opposite to the primary face. In this way, regions of increased conductivity and/or permittivity may in particular be formed in the vicinity of the secondary face opposite to the primary face.

In one embodiment, the carrier body comprises a base region made from the first material. At least one spatial region of the material composition is formed by adding particles of the additive second material to the first material in certain spatially confined portions of the carrier body.

In the region of the primary face, the carrier body may in particular be formed from the insulating first material only, such that the base region encompasses the primary face carrying the electrical contact elements for emitting electrical stimulation signals during a therapeutic action of the electrode device.

The primary face may in particular extend along a plane spanned by a first direction pointing along the longitudinal axis along which the lead body generally extends and a second direction transverse to the longitudinal axis. The carrier body herein has a length (measured along the first direction) in a range between 50 mm and 150 mm, a width (measured along the second direction) between 5 mm and 15 mm, and a thickness (measured along a third direction transverse to the first direction and the second direction) smaller than the width. The carrier body hence exhibits a generally flat shape. The carrier body may be flexibly

21.151P-WO 17.05.2024 deformable, such that it may be flexibly implantable for example in the region of the spinal column of a patient for providing neuro-stimulative therapy at the spinal cord.

The lead body extends from the flattened electrode end. The lead body may be flexibly deformable and may have a tubular shape, with an approximately circular cross section.

In another aspect, a method for fabricating a medical electrode device for implantation into a patient comprises: providing a lead body extending longitudinally along a longitudinal axis, at least one electrical line extending within the lead body; fabricating a flattened electrode end by forming at least a portion of a carrier body from a composition comprising an electrically insulating first material in which particles of an additive second material different than the first material are dispersed, and by arranging a multiplicity of electrical contact elements on a primary face of the carrier body for contacting tissue in proximity to the flattened electrode end in an implanted state of the medical electrode device; and arranging said flattened electrode end at a distal end of the lead body, wherein the arranging includes connecting the multiplicity of electrical contact elements to the at least one electrical line.

The advantages and advantageous embodiments described above for the medical electrode device equally apply also to the method.

DESCRIPTION OF THE DRAWINGS

The various features and advantages of the present invention may be more readily understood with reference to the following detailed description and the embodiments shown in the drawings. Herein,

Fig. 1 shows a view of an electrode device connected to a stimulation device in an implanted state in the area of the spine of a patient;

Fig. 2 shows a view of the electrode device in the epidural space in the region of the spinal column;

21.151P-WO 17.05.2024 Fig. 3 shows a view of a flattened electrode end of an embodiment of an electrode device;

Fig. 4 shows another view of a flattened electrode end of a medical electrode device;

Fig. 5 shows a schematic cross-sectional drawing of a flattened electrode end of a medical electrode device;

Fig. 6 shows a schematic cross-sectional drawing of the flattened electrode end, with particles of an additive second material dispersed in an insulating first material forming a carrier body of the second electrode end;

Fig. 7 shows a schematic cross-sectional drawing of another embodiment of a flattened electrode end;

Fig. 8A shows a schematic cross-sectional drawing of yet another embodiment of a flattened electrode end;

Fig. 8B shows the embodiment of Fig. 8 A, in a schematic top view;

Fig. 9 shows a schematic cross-sectional drawing illustrating the electrical behavior at the flattened electrode end;

Fig. 10 shows an embodiment of a flattened electrode end having additive second material implemented as rectangular elements;

Fig. 11 shows an embodiment of a flattened electrode end having additive second material implemented as flat rectangular layer;

Fig. 12 shows an embodiment of a flattened electrode end having additive second material implemented as round platelets;

21.151P-WO 17.05.2024 Fig. 13 shows an embodiment of a flattened electrode end having additive second material implemented as round flat rings;

Fig. 14 shows an embodiment of a flattened electrode end having additive second material implemented as flat stripes;

Fig. 15 shows lateral cross-sectional views of embodiments of a flattened electrode, depicting additive second material implemented as flat element located at different layers within the flattened electrode;

Fig. 16 shows an embodiment of a flattened electrode end having additive second material implemented as rectangular elements and additional conductive elements;

DETAILED DESCRIPTION

Subsequently, embodiments of the invention shall be described in detail with reference to the drawings. In the drawings, like reference numerals designate like structural elements.

It is to be noted that the embodiments are not limiting for the invention, but merely represent illustrative examples.

A medical electrode device 1, as shown in an embodiment in Figs. 1 and 2, is formed as a so-called paddle electrode and comprises a lead body 10 and a flattened electrode end 11 connected to the lead body 10 at a distal end 101 of the lead body 10, a plurality of contact elements being attached to the flattened electrode end 11 for injecting an electrical current e.g., in the region of the spinal column W of a patient P.

The electrode device 1 at a proximal end 100 of the lead body 10 is connected to a connector block 20 of a stimulation device 2, via which stimulation currents can be delivered to the

21.151P-WO 17.05.2024 electrode device 1 and output via the electrode arrangement arranged on the electrode end 11 to stimulate the spinal cord R in the region of the spinal column W.

As can be seen from the sectional view of Fig. 2, in the shown embodiment the electrode device 1 is implanted in the epidural space E in the region of the spinal column W of the patient P in such a way that the flattened electrode end 11 is located in the region of the spinal cord R and can thus introduce stimulation currents in a directed manner in order to effect nerve stimulation in the region of the spinal cord R.

While the lead body 10 for example comprises a circular (isodiametric) cross-section, the electrode device 1 is flattened in the area of the flattened electrode end 11 which, as can be seen in Figs. 3 and 4, carries a plurality of contact elements 12 evenly or unevenly spaced on the flattened electrode end 11 in such a way that stimulation energy can be fed in a directed manner for example into the spinal cord R of a patient P. The lead boy 10 generally extends longitudinally along a longitudinal axis L and herein is flexibly deformable to ease implantation in a patient P.

As visible from Fig. 3, each contact element 12 is connected to an electrical line 13, wherein each contact element 12 for example is connected to the stimulation device 2 via an associated, individual electrical line 13 and thus may be supplied with stimulation energy via the stimulation device 2 to emit electrical signals, or a group of electrical contact elements 12 is connected to a common electrical line 13 such that different groups of electrical contact elements 12 use different electrical lines 13. The electrical lines 13 are jointly routed as a single cable strand or, as illustrated in Fig. 4, as multiple cable strands in the lead body 10 in an encapsulated manner to the stimulation device 2.

As shown in Fig. 4, the contact elements 12 are arranged on a primary face 142 of a carrier body 14 and are exposed, in an implanted state, to tissue with electrical contact faces 120 facing outwards and can therefore come into electrical contact with surrounding tissue when the electrode device 1 is implanted in a patient. The flattened electrode end 11 at a proximal end 141 of the carrier body 14 is connected to the lead body 10.

21.151P-WO 17.05.2024 In an electrode device 1 as shown in Figs. 1 to 4, an arrangement of contact elements 12 is arranged on a carrier body 14 of a flattened electrode end 11, the flattened electrode end 11 having a paddle-like shape for placement in the epidural space E in the vicinity of the spinal column W. The contact elements 12 herein are placed on and embedded in the carrier body 14, such that the contact elements 12 each face outwards and are exposed to tissue with their contact face 120.

For fabricating the electrode device 1, the electrical lines 13 are connected to the contact elements 12, wherein for example an individual electrical line 13 is connected to each contact element 12, as illustrated in Fig. 3. The contact elements 12, e.g., with the electrical lines 13 connected thereto, are placed on the carrier body 14 to form an arrangement of contact elements 12 for providing for a stimulation and/or sensing in an implanted state of the electrode device 1.

Referring now to Fig. 5, the one or the multiple electrical lines 13 extending along the lead body 10 together with the associated primary electrical contact elements 12 arranged on the carrier element 14 of the flattened electrode end 11 form an electrical structure having a substantial physical length. If the patient P carrying the medical electrode device 1 undergoes an MRI examination, an RF excitation field as produced by an MRI device may couple into the electrical structure as formed by the electrical lines 13 and the primary electrical contact elements 12, wherein the electrical structure may exhibit a resonant behavior potentially causing a substantial field increase in the vicinity of the electrode device 1. As the primary electric contact elements 12 in the implanted position of the electrode device 1 are in contact with tissue in the surrounding of the flattened electrode end 11, this bears the risk of excessive heating in particular at the locations of the electrical contact elements 12.

Referring now to Fig. 6, in one embodiment the carrier body 14 is made from a material composition comprising an insulating first material, for example a polymer material such as polyurethane or silicone, in which particles 15 of an additive second material are dispersed. The second material is different from the first material. By adding the particles 15, the electrical characteristics of the carrier body 14 are modified, in particular for affecting an improved dissipation of RF energy at increased frequencies, in particular at frequencies

21.151P-WO 17.05.2024 typical for an RF excitation within an MRI device, while not substantially influencing the electrical behavior of the electrode device 1 for providing a stimulation therapy.

The particles 15 of the additive second material in particular may serve to modify the electrical conductivity and/or permittivity of the carrier body 14. For this, the second material may be a material which exhibits an increased conductivity and/or an increased permittivity in comparison to the first material.

For example, the particles 15 of the additive second material may be electrically conductive particles, for example made from a conductive carbon material, such as a graphite material or a conductive carbon compound material such as a tungsten carbon compound, e.g., tungsten carbide. Alternatively, the particles essentially consist of or comprise a metal, e.g., titanium.

In another example, the particles 15 of the additive second material may be particles of a material exhibiting an increased permittivity, for example made from dielectric ceramic material, e.g., barium titanate and/or titanium dioxide.

Also, a mixture of conductive particles and particles having an increased permittivity may be used.

The material composition for fabricating the carrier body 14 may for example comprise an amount of the particles of the additive second material in a range between 10 and 70 mass- %, for example in case of using barium titanate BaTiO3.The remainder of the material composition may be the first material, wherein also additional, other material components may be added to the composition.

By fabricating the carrier body 14 from a material composition comprising an insulating first material and particles 15 of an additive second material having an increased conductivity and/or an increased permittivity, in particular the capacitive reactance of the carrier body 14 may be modified. The capacitive reactance generally is inversely proportional to the frequency, such that with increasing frequency the capacitive reactance becomes smaller,

21.151P-WO 17.05.2024 causing a low capacitive coupling to surrounding tissue at increased frequencies, e.g., in the range of an applicable MRI frequency. As the frequency of a therapeutic stimulation signal is substantially lower than an MRI RF excitation frequency, the capacitive reactance at the therapeutic stimulation frequency is large, such that the emission of therapeutic stimulation signals is substantially not affected by the modification of the material of the carrier body 14. Hence, by adding particles 15 of an additive, second material having a higher electrical conductivity and/or a higher permittivity than the first material, the dissipation of RF energy at an increased frequency corresponding to an MRI excitation frequency may be improved in that RF energy is dissipated over the entire volume of the carrier body 14, such that a localized, excessive heating in particular at the locations of the electrical contact elements 12 at the primary face 142 of the carrier body 14 is prevented.

By e.g. increasing the permittivity of the carrier body 14 by adding particles 15 of a material exhibiting a high permittivity, the electric field density in the region of the carrier body 14 is increased when RF energy couples into the electrode device 1 during an MRI examination, wherein the RF energy is confined within the carrier body 14 and is not predominantly dissipated via the primary face 142, but via all faces of the carrier body 14, such that RF energy dissipation is directed away from the primary face 142 and hence from e.g. the spinal cord at which a therapeutic stimulation shall be achieved by means of the therapeutic contact elements 12.

Referring now to Fig. 7, in addition to using a material composition comprising an insulating first material in which particles 15 of an additive second material are dispersed, secondary contact elements 16 may be arranged on a secondary face 143 of the carrier body 14 opposite to the primary face 142. The secondary contact elements 16 serve as parasitic electrode poles, which are not connected to the arrangement of electrical lines 13 serving to contact the primary electrical contact elements 12 for feeding therapeutic stimulation signals to the contact elements 12. Rather, the parasitic secondary contact elements 16 are not connected to any electrical feeding structure and hence are electrically separate from the contact elements 12, the lines 13 and an active device connected to the lead body 10 at the proximal end of the lead body 10.

21.151P-WO 17.05.2024 The secondary contact elements 16 may be exposed towards the outside and may come into contact with surrounding tissue in an implanted state of the electrode device 1. In another embodiment, the secondary contact elements 16 may be covered towards the outside by an insulating material, for example by a coating material, or may be embedded within the material of the carrier body 14, such that the secondary contact elements 16 are not exposed towards the outside and do not come into electrical contact with surrounding tissue.

By means of the primary electrical contact elements 16, the dissipation of RF energy at the secondary face 143 of the flattened electrode end 11 may further be improved, such that energy dissipation is directed away from the primary face 142 of the carrier body 14.

The material composition comprising the insulating first material and the particles 15 of the additive second material may be used to fabricate the carrier body 14 as a whole. In another embodiment, only portions of the carrier body 14 may be formed by the material composition of the first material and the particles 15 of the second material.

Referring now to Figs. 8A and 8B, in one embodiment the spatial regions 144, 145 are formed by a material composition comprising the insulating first material and the particles 15 of the additive second material. A base region 140 of the carrier body 14 herein may be fabricated for example from the insulating first material, the spatially confined regions 144, 145 being distinguished from the base region 140 in that particles 15 of the additive second material are added to the first material within the regions 144, 145.

In the embodiment of Figs. 8A and 8B, the spatial regions 144, 145 are arranged in the vicinity of the secondary face 143 and hence are distant from the primary face 142 at which the therapeutic contact elements 12 are placed. As visible from the schematic cross-sectional view of Fig. 8A in view of the top view of the secondary face 143 of Fig. 8B, the spatial regions 144, 145 may have a substantially cubic shape and may be formed in the region of the secondary face 143 to substantially function as counter electrodes counter to the contact elements 12 for dissipating energy at the secondary face 143.

21.151P-WO 17.05.2024 Referring now to Fig. 9, by the means described herein the electrical behavior of the carrier body 14 at increased frequencies, in particular at an applicable MRI frequency, may be modified such that an increased capacitance C and conductance G is provided across the thickness of the flattened electrode end 11. By modifying the electrical characteristics of the carrier body 14, potentially in conjunction with providing additional, parasitic electrode poles 16 at the secondary face 143 opposite the primary face 142, an RF energy dissipation may be distributed over the entire volume of the carrier body 14 of the flattened end 11, in particular preventing a concentration of RF energy in the region of the primary face 142, in particular at the locations of the primary electrical contact elements 12.

As an excessive heating at the flattened electrode end 11 is prevented, a risk for a patient during an MRI examination, such as a full body MRI scan, is reduced.

For fabricating an electrode device 1 as described herein, a lead body 10 is provided. A flattened electrode end 11 is fabricated by forming a carrier body 14 from a material composition comprising an insulating first material in which particles 15 of an additive second material are dispersed. Primary electrical contact elements 12 are placed on the carrier body 14, wherein prior to or after placing the primary electrical contact elements 12 on the carrier body 14, the primary electrical contact elements 12 are connected to associated electrical lines 13 received within the lead body 10. The carrier body 14, with primary contact elements 12 arranged thereon or prior to arranging the contact elements 12 on the carrier body 14, is fixed to the lead body 10.

Referring to Fig. 10, an embodiment of the flattened electrode end 301 is depicted as cross- sectional view. Within the flattened electrode end 301, additive second material implemented as flat rectangular plates 302. Electrical contact elements 303 are located on one of the two large surfaces of the flattened electrode end. The flattened electrode end is depicted in full view 304.

In Fig. 11, an embodiment of the flattened electrode end 311 is depicted as cross-sectional view. Within the flattened electrode end 311, additive second material implemented as flat

21.151P-WO 17.05.2024 rectangular layer 312 which extends along almost the entire surface of the flattened electrode end. The flattened electrode end is depicted in full view 314.

Fig. 12 an embodiment of the flattened electrode end 321 is depicted as cross-sectional view. Within the flattened electrode end 321, additive second material implemented as round platelets 322. Electrical contact elements 323 are located on one of the two large surfaces of the flattened electrode end. The flattened electrode end is depicted in full view 324.

In Fig. 13, an embodiment of the flattened electrode end 331 is depicted as cross-sectional view. Within the flattened electrode end 331, additive second material implemented as round flat rings 332. Electrical contact elements 333 are located on one of the two large surfaces of the flattened electrode end. The flattened electrode end is depicted in full view 334.

In Fig. 14, an embodiment of the flattened electrode end 341 is depicted as first cross- sectional view. Within the flattened electrode end 341, the additive second material is implemented as flat rectangular stripe 342 and which extends across the width of the flattened electrode end 341. Electrical contact elements 343 are located on one of the two large surfaces of the flattened electrode end. Second cross-sectional view 344 is a lateral view on flattened electrode end 341, showing two neighboring flat rectangular stripes 345. The flattened electrode end is depicted in full view 346.

Fig. 15 shows cross-sectional views of embodiments of a flattened electrode, depicting additive second material implemented as flat element located at different layers within the flattened electrode. In cross-sectional view a), additive second material 352 is located in the middle layer within flattened electrode end 351. In cross-sectional view b), additive second material 354 is located in the lower layer within flattened electrode end 353, close to the electrical contact elements. In cross-sectional view c), additive second material 356 is implemented as upper half of flattened electrode end 355. In the last embodiment, additive second material 356 would contact surrounding tissue in the implanted state.

Fig. 16 shows an embodiment of a flattened electrode end having additive second material implemented as rectangular elements and additional conductive elements.

21.151P-WO 17.05.2024 In Fig. 16, an embodiment of the flattened electrode end 361 is depicted as first cross- sectional view. Within the flattened electrode end 361, the additive second material is implemented as flat rectangular plates 363. Electrical contact elements 343 are located on one of the two large surfaces of the flattened electrode end. Secondary contact elements 362 are located on the second of the two large surfaces of the flattened electrode end, above the flat rectangular plates 363. Preferably, a secondary contact element 362 has a similar or the same rectangular shape as of flat rectangular plate 363. The flattened electrode end is depicted in full view 365.

It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.

21.151P-WO 17.05.2024 LIST OF REFERENCE NUMERALS

I Implantable electrode device

10 Lead body

100 Proximal end

101 Distal end

I I Electrode end

12 Contact element

120 Contact face

13 Electrical line

14 Carrier body

140 Base

141 Proximal end

142, 143 Face

144, 145 Modified regions

15 Particles (additive material)

2 Stimulation device

20 Connector block

C Capacitance

E Epidural space

G Conductance (resistance)

L Longitudinal axis

P Patient

R Spinal cord

W Spinal column

21.151P-WO 17.05.2024

Claims

1. A medical electrode device (1) for implantation into a patient (P), comprising: a lead body (10) extending longitudinally along a longitudinal axis (L); at least one electrical line (13) extending within the lead body (10); and a flattened electrode end (11) arranged at a distal end of the lead body (10) and comprising a carrier body (14) and at least one primary electrical contact element (12) connected to the at least one electrical line (13), wherein the at least one electrical contact elements (12) is arranged on a primary face (142) of the carrier body (14) and configured to contact tissue in proximity to the flattened electrode end (11) in an implanted state of the medical electrode device (1), wherein at least a portion of the carrier body (14) is made from a material composition comprising an electrically insulating first material in which particles (15) of an additive second material different than the first material are dispersed.

2. The medical electrode device (1) according to claim 1, wherein the first material is a polyurethane or silicone material.

3. The medical electrode device (1) according to claim 1 or 2, wherein the additive second material is characterized by an a higher electrical conductivity than the first material.

4. The medical electrode device (1) according to claim 3, wherein the additive second material essentially consists of or comprises a conductive carbon material, in particular a conductive carbon compound, more particular a tungsten carbon compound or a metal, particularly tungsten.

5. The medical electrode device (1) according to one of the preceding claims, wherein the additive second material is characterized by a higher permittivity than the first material.

21.151P-WO 17.05.2024

6. The medical electrode device (1) according to claim 5, wherein the additive second material comprises or essentially consist of a dielectric ceramic material, particularly barium titanate and/or titanium dioxide.

7. The medical electrode device (1) according to one of the preceding claims, wherein the material composition comprises an amount of said additive second material in a range between 10 and 70 mass-%.

8. The medical electrode device (1) according to one of the preceding claims, wherein the flattened electrode end (11) comprises at least one secondary contact element (16) arranged on a secondary face (143) of the carrier body (14) facing away from said primary face (142).

9. The medical electrode device (1) according to claim 8, wherein said at least one secondary contact element (16) is not electrically connected to said at least one electrical line (13).

10. The medical electrode device (1) according to one of the preceding claims, wherein said carrier body (14) comprises at least one spatial region (144, 145) made from said material composition.

11. The medical electrode device (1) according to claim 10, wherein said at least one spatial region (144, 145) is spatially distant, along a direction perpendicular to said primary face (142), from said primary face (142).

12. The medical electrode device (1) according to claim 10 or 11, wherein said carrier body (14) comprises a base region (140) made from said first material.

13. The medical electrode device (1) according to claim 12, wherein said base region (14) forms said primary face (142).

21.151P-WO 17.05.2024

14. The medical electrode device (1) according to one of the preceding claims, characterized in that said primary face (142) extends along a plane spanned by a first direction pointing along said longitudinal axis (L) and a second direction transverse to said longitudinal axis (L), wherein the carrier body (14) has a length, measured along the first direction, in a range between 50 mm and 150 mm, a width, measured along the second direction, between 5 mm and 15 mm and a thickness, measured along a third direction transverse to the first direction and the second direction, smaller than said width.

15. A method for fabricating a medical electrode device (1) for implantation into a patient (P), the method comprising: providing a lead body (10) extending longitudinally along a longitudinal axis (L), at least one electrical line (13) extending within the lead body (10); fabricating a flattened electrode end (11) by forming at least a portion of a carrier body (14) from a composition comprising an electrically insulating first material in which particles (15) of an additive second material different than the first material are dispersed, and by arranging a multiplicity of electrical contact elements (12) on a primary face (142) of the carrier body (14) for contacting tissue in proximity to the flattened electrode end (11) in an implanted state of the medical electrode device (1); and arranging said flattened electrode end (11) at a distal end of the lead body (10), wherein the arranging includes connecting the multiplicity of electrical contact elements (12) to the at least one electrical line (13).

21.151P-WO 17.05.2024