WO2017027045A1

WO2017027045A1 - Cochlear implants having bone-anchored magnet apparatus and associated methods

Info

Publication number: WO2017027045A1
Application number: PCT/US2015/045154
Authority: WO
Inventors: William L. Johnson; Jugal Yatinkumar KAPADIA
Original assignee: Advanced Bionics Ag
Priority date: 2015-08-13
Filing date: 2015-08-13
Publication date: 2017-02-16

Abstract

A cochlear implant including a cochlear lead, a housing defining a magnet recess, with an open end and a bottom wall defining an aperture that extends through the bottom wall, and an antenna region that surrounds the magnet recess, an antenna within the housing antenna region, a stimulation processor within the housing operably connected to the antenna and to the cochlear lead, and a bone-anchored magnet apparatus including a magnet located within the magnet recess and an anchor, associated with the magnet, that extends through the bottom wall aperture.

Description

COCHLEAR IMPLANTS HAVING BONE-ANCHORED MAGNET APPARATUS AND ASSOCIATED METHODS

BACKGROUND

1 . Field

The present disclosure relates generally to the implantable portion of implantable cochlear stimulation (or "ICS") systems.

2. Description of the Related Art

ICS systems are used to help the profoundly deaf perceive a sensation of sound by directly exciting the intact auditory nerve with controlled impulses of electrical current. Ambient sound pressure waves are picked up by an externally worn microphone and converted to electrical signals. The electrical signals, in turn, are processed by a sound processor, converted to a pulse sequence having varying pulse widths and/or amplitudes, and transmitted to an implanted receiver circuit of the ICS system. The implanted receiver circuit is connected to an implantable electrode array that has been inserted into the cochlea of the inner ear, and electrical stimulation current is applied to varying electrode combinations to create a perception of sound. The electrode array may, alternatively, be directly inserted into the cochlear nerve without residing in the cochlea. A representative ICS system is disclosed in U.S. Patent No. 5,824,022, which is entitled "Cochlear Stimulation System Employing Behind- The-Ear Sound processor With Remote Control" and incorporated herein by reference in its entirety. Examples of commercially available ICS sound processors include, but are not limited to, the Advanced Bionics™ Harmony™ BTE sound processor, the Advanced Bionics™ Naida™ BTE sound processor and the Advanced Bionics™ Neptune™ body worn sound processor.

As alluded to above, some ICS systems include an implantable cochlear stimulator (or "cochlear implant"), a sound processor unit (e.g., a body worn processor or behind-the-ear processor), and a microphone that is part of, or is in communication with, the sound processor unit. The cochlear implant communicates with the sound processor unit and, some ICS systems include a headpiece that is in communication with both the sound processor unit and the cochlear implant. The headpiece communicates with the cochlear implant by way of a transmitter (e.g., an antenna) on the headpiece and a receiver (e.g., an antenna) on the implant. Optimum communication is achieved when the transmitter and the receiver are aligned with one another. To that end, the headpiece and the cochlear implant may include respective positioning magnets that are attracted to one another, and that maintain the position of the headpiece transmitter over the implant receiver. The implant magnet may, for example, be located within a pocket in the cochlear implant housing.

The present inventor has determined that conventional cochlear implants are susceptible to improvement. For example, the magnets in many conventional cochlear implants are disk-shaped and have north and south magnetic dipoles that are aligned in the axial direction of the disk. Such magnets are not compatible with magnetic resonance imaging ("MRI") systems. In particular, the cochlear implant 10 illustrated in FIG. 1 includes, among other things, a housing 12 and a disk-shaped solid block magnet 14. The implant magnet produces a magnetic field M in a direction that is perpendicular to the patient's skin and parallel to the axis A, and this magnetic field direction is not aligned with, and may be perpendicular to (as shown), the direction of the MRI magnetic field B. The misalignment of the interacting magnetic fields M and B is problematic for a number of reasons. The dominant MRI magnetic field B (typically 1 .5 Tesla or more) may generate a significant amount of torque T on the implant magnet 14. The torque T may dislodge the implant magnet 14 from the pocket within the housing 12, reverse the magnet 14 and/or dislocate the cochlear implant 10, all of which may also induce tissue damage. One proposed solution involves surgically removing the implant magnet 14 prior to the MRI procedure and then surgically replacing the implant magnet thereafter. The present inventors have determined that a solution which does not involve surgery would be desirable. SUMMARY

A cochlear implant in accordance with one of the present inventions includes a cochlear lead, a housing defining a magnet recess, with an open end and a bottom wall defining an aperture that extends through the bottom wall, and an antenna region that surrounds the magnet recess, an antenna within the housing antenna region, a stimulation processor within the housing operably connected to the antenna and to the cochlear lead, and a bone- anchored magnet apparatus including a magnet located within the magnet recess and an anchor, associated with the magnet, that extends through the bottom wall aperture. The present inventions also include systems with such a cochlear implant in combination with a headpiece.

A method in accordance with one of the present inventions includes the step of securing a magnet to a skull by driving a bone screw through a portion of a cochlear implant housing, in which a sound processor and an antenna are located, and into the skull such that the bone screw anchors the magnet relative to the skull.

A method in accordance with one of the present inventions includes the step of securing a magnet to a skull by driving a screw through a portion of a cochlear implant housing, in which a sound processor and an antenna are located, and into a base that is secured to the skull such that the magnet is anchored relative to the skull.

There are a number of advantages associated with such apparatus and methods. For example, the torque applied to the implant magnet by a strong magnetic field, such as an MRI magnetic field, will not dislodge the implant magnet from the within the housing, reverse the magnet and/or dislocate the cochlear implant. As a result, surgical removal of the cochlear implant magnet prior to an MRI procedure, and then surgical replacement thereafter, is not required.

The above described and many other features of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of the exemplary embodiments will be made with reference to the accompanying drawings. FIG. 1 is a side view showing a conventional cochlear implant in an MRI magnetic field.

FIG. 2 is a plan view of a cochlear implant in accordance with one embodiment of a present invention.

FIG. 3 is a section view of a portion of the cochlear implant illustrated in FIG. 2 with the bone-anchored magnet apparatus removed.

FIG. 4 is a perspective view of the bone-anchored magnet apparatus illustrated in FIG. 2.

FIG. 5 is a section view take along line 5-5 in FIG. 4.

FIG. 6 is a section view of another exemplary bone-anchored magnet apparatus.

FIG. 7 is a section view of a portion of the cochlear implant illustrated in FIG. 2 with the bone-anchored magnet apparatus anchored to bone.

FIG. 8 is a plan view of a cochlear implant in accordance with one embodiment of a present invention.

FIG. 9 is a section view of the bone-anchored magnet apparatus illustrated in FIG. 8.

FIG. 10 is a section view of a portion of the cochlear implant illustrated in FIG. 8 with the bone-anchored magnet apparatus anchored to bone.

FIG. 1 1 is a section view of a cochlear implant in accordance with one embodiment of a present invention.

FIG. 12 is an exploded section view of the cochlear implant illustrated in FIG. 1 1 .

FIG. 13 is a block diagram of a cochlear implant system in accordance with one embodiment of a present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.

One example of a cochlear implant (or "implantable cochlear stimulator") in accordance with the present inventions is the cochlear implant 100 illustrated in FIG. 2. The cochlear implant 100 includes a flexible housing 102 formed from a silicone elastomer or other suitable material, a processor assembly 104, a cochlear lead 106, and an antenna 108 that may be used to receive data and power by way of an external antenna that is associated with, for example, a sound processor unit. The flexible housing 102 includes a processor portion 103 in which the processor assembly 104 is located and an antenna portion 105 in which the antenna 108 is located. The cochlear lead 106 may include a flexible body 1 10, an electrode array 1 12 at one end of the flexible body 102, and a plurality of wires (not shown) that extend through the flexible body from the electrodes 1 14 (e.g., platinum electrodes) in the array 1 12 to the other end of the flexible body. The exemplary antenna 108 is a coil antenna with one or more loops (or "turns"), and three loops are shown in the illustrated embodiment. The exemplary processor assembly 104, which is connected to the electrode array 1 12 and antenna 108, includes a printed circuit board 1 16 with a stimulation processor 1 18 that is located within a hermetically sealed case 120. The stimulation processor 1 18 converts stimulation data into stimulation signals that stimulate the electrodes 1 14 of the electrode array 1 12.

The exemplary cochlear implant also includes a bone-anchored magnet apparatus (or "BAM apparatus") 122 that is located within a recess 124 (FIG. 3) in the flexible housing 102, surrounded by the housing antenna portion 105, and encircled by the antenna 108. The magnetic aspect of the BAM apparatus 122 insures that an external antenna (discussed below) will be properly positioned relative to the antenna 108, while the bone anchor aspect prevents the BAM apparatus from moving when exposed to a strong a magnetic field such as an MRI magnetic field. To that end, and referring to FIGS. 4 and 5, the exemplary BAM apparatus 122 includes a magnet 126 and an anchor in the form of a bone screw 128. The bone screw 128 has a shank 130 with threads 132 as well as a head 134 with an internal volume 136 in which the magnet 126 is located. The dimensions of the internal volume 136 correspond to those of the outer surface of the magnet 126. The head 134 also has a slot 138 (or other instrumentality) that is configured to receive a screwdriver or other tool. It should also be noted that, once manufacture is complete, the exemplary BAM apparatus 122 is a unitary object that may not be separated into its component parts without destruction of the object.

To accommodate the BAM apparatus 122, the recess 124 (FIG. 3) in the flexible body 102 includes an open end 140 and a bottom wall 142 with an aperture 144 through which the threaded shank 130 passes as the bone screw 128 is screwed into bone. The size and shape of the head 134 is essentially the same as that of the recess 124, which allows the head to be positioned within the recess in the manner described below with reference to FIG. 7.

Although not limited to any particular configurations, the exemplary bone screw head 134 includes a base 146 and a cover 148 that may be secured to base after the magnet 126 has been placed into the base. The cover 148 may be secured to the base 146 in such a manner that a hermetic seal is formed between the cover and the base. Suitable techniques for securing the cover 148 to the base 146 include, for example, seam welding with a laser welder. The threaded shank 130 may be separately manufactured and connected to the screw head 134, or the shank 130 and base 146 may be formed from a single blank.

With respect to materials, the bone screw 128 may be formed from, for example, biocompatible metals and/or plastics. Such materials may, in some instances, be non-magnetic or paramagnetic. Suitable materials include, but are not limited to, titanium or titanium alloysand polytetrafluoroethylene ("PTFE"). In particular, exemplary metals include commercially pure titanium (e.g., Grade 2) and the titanium alloy Ti-6AI-4V (Grade 5). In other implementations, the entire bone screw may be formed from magnetic material and coated with a biocompatible metal through use of a deposition process. With respect to size and shape, the screw head 134 may have an overall size and shape similar to that of conventional cochlear implant magnets. The exemplary screw head 134 is disk-shaped and, in some implementations, the diameter may range from 9 mm to 16 mm and the thickness may range from 1 .5 mm to 3.0 mm. The diameter of the screw head 134 is 12.9 mm, and the thickness is 2.4 mm, in the illustrated embodiment.

In some instances, magnetic field induced rotation of the magnet 126 within the screw head internal volume 136 about its central axis may be prevented, while in other instances such rotation may be permitted. In those instances where rotation is permitted, the inner surface of the screw head 134 may include a lubricious layer (not shown). The lubricious layer may be in the form of a specific finish of the inner surface that reduces friction, as compared to an unfinished surface, or may be a coating of a lubricious material such as polytetrafluoroethylene (PTFE), parylene, or fluorinated ethylene propylene (FEP).

The exemplary BAM apparatus 122a illustrated in FIG. 6 is substantially similar to BAM apparatus 122 (FIG. 5) and similar elements are represented by similar reference numerals. Here, however, a shim 150 is inserted into the screw head 134 to focus the magnetic field created by the magnet 126. When the associated cochlear implant is implanted, the shim 150 (sometimes referred to as a "flux guide") will increase the flux density and focus the magnetic field toward the patient's skin and an externally worn headpiece. Although the present shims are not so limited, the exemplary shim 150 is cup-shaped and may be about 0.25 mm thick and formed from iron or from a nickel-iron alloy, referred to as mu-metal, that is composed of approximately 77% nickel, 16% iron, 5% copper and 2% chromium or molybdenum. In other implementations, a flat disk positioned at the bottom of the screw head 134 may be employed.

Turning to FIG. 7, the cochlear implant 100 may be secured (or

"anchored") to the skull by inserting the BAM apparatus 122 (or other BAM apparatus with a bone screw that is disclosed herein) into the recess 124 with the end of the shank 130 in the aperture 144. The bone screw 128 may then be rotated (or "driven") until the threaded portion of the shank 130 is anchored to the bone B and the screw head 134 is fully seated within the recess 124, and on bottom wall 142 (FIG. 7). The magnet 126 is at this point positioned within the housing 102 and anchored to the patient in such a manner that the torque generated by an MRI magnetic field will not dislodge the magnet from the housing 102, reverse the magnet within the housing, and/or dislocate the cochlear implant 100.

Another exemplary cochlear implant is illustrated in FIGS. 8 and 9. Cochlear implant 100b is substantially similar to cochlear implant 100 and similar elements are represented by similar reference numerals. Here, however, the bone screw and magnet are separate structures that are usable together. To that end, the BAM apparatus 122b includes an anchor, in the form of a bone screw 152, and an annular magnet 154 with a biocompatible coating 156. The exemplary bone screw 152 has a shank 158 with threads 160 as well as a head 162 with a cross-shaped recess 164, while the annular magnet 154 has an aperture 166 through which the shank passes. The bone screw 152 and coating 156 may be formed from a biocompatible metal and/or a plastic such as those discussed above. The respective dimensions of the recess 124, bone screw 152 and annular magnet 154 may be such that when the annular magnet is positioned within the recess, the shank 158 will pass through the aperture 166, and the head 162 will extend over the top surface (in the illustrated orientation) of the magnet.

Turning to FIG. 10, the cochlear implant 100b may be secured (or "anchored") to the skull by inserting annular magnet 154 of the BAM apparatus 122b into the recess 124, and passing the shank 158 through the magnet aperture 166 until the end of the shank is in the aperture 144. The bone screw 152 may then be rotated until the threaded portion of the shank 158 is anchored to the bone B and the magnet 154 is fully seated within the recess 124 and against the bottom wall 142. The magnet 154 is at this point positioned within the housing 102 and anchored to the patient in such a manner that the torque generated by an MRI magnetic field will not dislodge the magnet from the housing 102, reverse the magnet within the housing, and/or dislocate the cochlear implant 100b.

Another exemplary cochlear implant is generally represented by reference numeral 100c in FIGS. 1 1 and 12. Cochlear implant 100c is substantially similar to cochlear implant 100 and similar elements are represented by similar reference numerals. Here, however, the BAM apparatus 122c is a two-piece, separable structure that includes an anchor 168 and a magnet 126. The anchor 168 has a first portion that is configured to be secured to the bone B and a second portion, in which the magnet 126 is located, that is configured to be secured to the first portion. In the illustrated embodiment, the first portion includes a base 170 and an aperture 171 (with threads 172) extending completely through the base (as shown) or partially through the base. The first portion may be positioned within a recess 174 that is formed in the bone B. A biocompatible adhesive 176 may be used to permanently secure the base 170 to the bone B. Formation of fibrous tissue around the base 170 will enhance the rigidity and stability of the connection to the bone. The second portion is a screw 128c that includes a shank 130c with threads 132c (which are complimentary to the threads 172) and a head 134 that is connected to the shank. The head 134, which defines an internal volume 136, includes a base 146 and a cover 148 that may be secured to one other in the manner described above. The screw 128c and anchor 168 may be formed from the materials described above in the context of the bone screw 128, and/or may be configured to prevent or permit rotation of the magnet 126, and/or may or may not include a shim such as that disclosed in the context of FIG. 6.

It should be noted that the screw and threaded aperture arrangement illustrated in FIGS. 1 1 and 12 is only one example of a mechanical fastener system that may be used to secure a magnet to a base. By way of example, but not limitation, the relative locations of the male and female threads may be reversed, and other mechanical interlocks, including those that do and do not involve rotation of one portion relative to another, may be employed in other embodiments.

With respect to placement and removal, the exemplary head 134 includes a slot 138 (or other instrumentality) that is configured to receive a screwdriver or other tool. The cochlear implant 100c may be secured (or "anchored") to the skull by inserting the screw 128c into the recess 124, with the shank 130c extending through the housing aperture 144 and into the threaded aperture 171 of the base 170. The screw 128c may then be rotated (or "driven") until the threaded portion of the shank 130c is connected to the base 170 and the screw head 134 is fully seated within the recess 124, and on bottom wall 142 (FIG. 1 1 ). Removal of the magnet 126, if necessary, may be accomplished by simply rotating the screw 128c out of engagement with the base 170.

There are a variety of advantages associated with cochlear implants described above. For example, the torques associated with the MRI magnetic field B (typically 1 .5 Tesla or more) will not dislodge the BAM apparatus from the associated cochlear implant. As a result, surgical removal of a cochlear implant magnet prior to an MRI procedure, and then surgical replacement thereafter, is not required. Nevertheless, the use of a screw allows the BAM apparatus, or the portion of the BAM apparatus including the magnet, to be removed if necessary.

Turning to FIG. 13, the exemplary cochlear implant system 50 includes the cochlear implant 100 (or one of the other cochlear implants described above), a sound processor, such as the illustrated body worn sound processor 200 or a behind-the-ear sound processor, and a headpiece 300.

The exemplary body worn sound processor 200 in the exemplary ICS system 50 includes a housing 202 in which and/or on which various components are supported. Such components may include, but are not limited to, sound processor circuitry 204, a headpiece port 206, an auxiliary device port 208 for an auxiliary device such as a mobile phone or a music player, a control panel 210, one or microphones 212, and a power supply receptacle 214 for a removable battery or other removable power supply 216 (e.g., rechargeable and disposable batteries or other electrochemical cells). The sound processor circuitry 204 converts electrical signals from the microphone 212 into stimulation data. The exemplary headpiece 300 includes a housing 302 and various components, e.g., a RF connector 304, a microphone 306, an antenna (or other transmitter) 308 and a positioning magnet apparatus 310, that are carried by the housing. The magnet apparatus 310 may consist of a single magnet or may consist of one or more magnets and a shim. The headpiece 300 may be connected to the sound processor headpiece port 206 by a cable 312. The positioning magnet apparatus 310 is attracted to the BAM apparatus 122 of the cochlear stimulator 100, thereby aligning the antenna 308 with the antenna 108. The stimulation data and, in many instances power, is supplied to the headpiece 300. The headpiece 300 transcutaneously transmits the stimulation data, and in many instances power, to the cochlear implant 100 by way of a wireless link between the antennas. The stimulation processor 1 18 converts the stimulation data into stimulation signals that stimulate the electrodes 1 14 of the electrode array 1 12. In at least some implementations, the cable 312 will be configured for forward telemetry and power signals at 49 MHz and back telemetry signals at 10.7 MHz. It should be noted that, in other implementations, communication between a sound processor and a headpiece and/or auxiliary device may be accomplished through wireless communication techniques. Additionally, given the presence of the microphone(s) 212 on the sound processor 200, the microphone 306 may be also be omitted in some instances. The functionality of the sound processor 200 and headpiece 300 may also be combined into a single head wearable sound processor. Examples of head wearable sound processors are illustrated and described in U.S. Patent Nos. 8,81 1 ,643 and 8,983,102, which are incorporated herein by reference in their entirety.

Although the inventions disclosed herein have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the inventions include any combination of the elements from the various species and embodiments disclosed in the specification that are not already described. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.

Claims

We claim: 1 . A cochlear implant, comprising:

a cochlear lead including a plurality of electrodes; a housing defining a magnet recess, with an open end and a bottom wall defining an aperture that extends through the bottom wall, and an antenna region that surrounds the magnet recess;

an antenna within the housing antenna region;

a stimulation processor within the housing operably connected to the antenna and to the cochlear lead; and

a bone-anchored magnet apparatus including a magnet located within the magnet recess and an anchor, associated with the magnet, that extends through the bottom wall aperture.

2. A cochlear implant as claimed in claim 1 , wherein

the housing comprises a flexible housing; and

the antenna and the stimulation processor are embedded within a flexible housing.

3. A cochlear implant as claimed in claim 1 , wherein

the anchor comprises a bone screw that includes a head and a threaded shank; and

the magnet is located within the head.

4. A cochlear implant as claimed in claim 3, wherein

the bone screw is formed from a biocompatible metal.

5. A cochlear implant as claimed in claim 1 , wherein

wherein the magnet comprise an annular magnet defining an aperture; and

the anchor comprises a bone screw with a threaded shank that extends through the magnet aperture.

6. A cochlear implant as claimed in claim 5, wherein

the annular magnet is coated with a biocompatible metal.

7. A cochlear implant as claimed in claim 5, wherein

the bone screw includes a head; and

the annular magnet is located between the head and the bottom wall of the magnet recess.

8. A cochlear implant as claimed in claim 1 , wherein

the anchor includes a screw with a head in which the magnet is located; and

the entire antenna is located outside the screw.

9. A cochlear implant as claimed in claim 1 , wherein

the antenna comprises a coil antenna that defines a central axis; and

at least a portion of the anchor is located on the central axis.

10. A cochlear implant as claimed in claim 1 , wherein

the anchor includes a first portion that is configured to be secured to bone and a second portion, in which the magnet is located, that is configured to be connected to the first portion.

1 1 . A cochlear implant as claimed in claim 10, wherein

the first portion includes a threaded shank; and

the second portion includes a threaded aperture.

12. A system, comprising

a cochlear implant as claimed in any one of claims 1 -1 1 ; and a headpiece including

an antenna, and

a headpiece magnet associated with the antenna that is attracted to the implant magnet.

13. A method, comprising:

securing a magnet to a skull by driving a bone screw through a portion of a cochlear implant housing, in which a sound processor and an antenna are located, and into the skull such that the bone screw anchors the magnet relative to the skull.

14. A method as claimed in claim 13, wherein

the magnet is located within the bone screw.

15. A method as claimed in claim 13, wherein

the magnet includes an aperture and the bone screw is located within the aperture.

16. A method as claimed in claim 13, wherein

the cochlear implant housing includes a magnet recess, with an open end and a bottom wall defining an aperture that extends through the bottom wall; and

the portion of the cochlear implant housing through which the bone screw is driven is the bottom wall aperture.

17. A method, comprising:

securing a magnet to a skull by driving a screw through a portion of a cochlear implant housing, in which a sound processor and an antenna are located, and into a base that is secured to the skull such that the magnet is anchored relative to the skull.

18. A method as claimed in claim 17, wherein

the magnet is located within the screw.

19. A method as claimed in claim 17, wherein

the cochlear implant housing includes a magnet recess, with an open end and a bottom wall defining an aperture that extends through the bottom wall; and the portion of the cochlear implant housing through which the screw is driven is the bottom wall aperture.