Cochlear implant device

Abstract

The present disclosure relates to a cochlear implant device comprising: a plurality of optical waveguides having different lengths; and an optical transmitter that makes light incident on an optical waveguide according to a sound frequency. The light emission positions of the plurality of optical waveguides correspond to the sensitivity of the sound frequency in a cochlea.

Description

cochlear implant device

[0001] The present disclosure relates to a cochlear implant device worn on the human body, and more particularly to a cochlear implant device that uses light.

[0002] It is said that if children with congenital hearing loss are diagnosed early and given appropriate support, it will have a positive impact on their overall development. For this reason, newborn hearing screening tests are becoming more common, and it is expected that the number of newborns with early detection of hearing loss will increase in the future. In addition, as the population ages, it is expected that the number of people who develop age-related hearing loss will also increase. For these reasons, it is extremely important to restore hearing lost due to hearing loss.

[0003] Hearing aids and cochlear implants are used to restore hearing. Hearing aids cannot be used if even some of the hair cells are not functioning. On the other hand, cochlear implants can be used even if the hair cells are severely damaged. For this reason, electrically stimulating cochlear cells are now widely used, as they transmit sound.

[0004] Cochlear implants are said to be one of the most successful artificial organs, with approximately 10,000 to 30,000 people in Japan currently fitted with them. Electrical stimulation-type cochlear implants still have difficulty extracting a speaker's words from noise, such as in a crowded street, compared to people with normal hearing. To solve these problems, optical cochlear implant devices that use light to stimulate cochlear cells are being investigated (see, for example, Non-Patent Document 1). Infrared light has low toxicity to biological cells and penetrates deep into cochlear cells, making it a promising option.

[0005] However, when considering safety for the human body and ease of maintenance, a passive type (a type in which the light source is attached to the outside of the body and the light is delivered to the inside of the body via a fiber) is considered preferable (see, for example, Non-Patent Document 2). On the other hand, it has been demonstrated that stimulating cochlear cells with multiple lights can result in clearer hearing. What has been demonstrated here is an active type, i.e., a technology in which a light source is embedded inside the body to irradiate multiple lights (see, for example, Non-Patent Document 3).

[0006] Dieter, Alexander, Daniel Keppeler, and Tobias Moser. “Towards the optical cochlear implant: optogenetic approaches for hearing restoration.” EMBO molecular medicine 12.4 (2020): e11618. Gundelach, Lili A. , et al. “Towards the clinical translation of optogenetic skeletal muscle stimulation.” Pfluegers Archiv-European Journal of Physiology 472.5 (2020): 527-545. Keppeler, Daniel, et al. “Multichannel optogenetic stimulation of the auditory pathway using microfabricated LED cochlear implants in ” Science Translational Medicine 12.553 (2020): eabb8086.

[0007] Non-Patent Document 2 indicates that a passive type internally mounted unit is desirable, but in order to stimulate cochlear cells with multiple light beams, it was necessary to use an active type internally mounted unit as in Non-Patent Document 3. Therefore, an object of the present disclosure is to provide a cochlear implant device that is a passive type but can stimulate cochlear cells in multiple locations.

[0008] In order to achieve the above object, the cochlear implant device according to the present disclosure includes a plurality of optical waveguides of different lengths and an optical transmitter that directs light into the optical waveguides according to sound frequencies, and the light emission positions of the plurality of optical waveguides correspond to the sensitivity of the sound frequencies within the cochlea.

[0009] The cochlear implant device of the present disclosure may include an external attachment unit that includes the optical transmitter and is attached outside the human body, and an internal attachment unit that includes the plurality of optical waveguides and is attached inside the human body.

[0010] The externally worn unit may include a microphone that converts sound into an electrical signal, and a sound processor that outputs sound intensity for each sound frequency by analyzing the frequency components of the electrical signal from the microphone. The optical transmitter outputs light having a light intensity corresponding to the sound intensity to an optical waveguide corresponding to the sound frequency from the sound processor among the plurality of optical waveguides.

[0011] The internally mounted unit includes an output unit that extracts light at a different position for each of the plurality of optical waveguides. For example, the plurality of optical waveguides may be configured to be cut at an angle. Alternatively, an oblique diffraction grating may be provided in any of the plurality of optical waveguides. Alternatively, a Y-shaped waveguide may be provided in any of the plurality of optical waveguides. Alternatively, any of the plurality of optical waveguides may be configured to be cut at an angle. Alternatively, a reflection filter may be provided in any of the plurality of optical waveguides.

[0012] The above disclosures can be combined as much as possible.

[0013] According to the present disclosure, it is possible to provide a passive cochlear implant device that can stimulate cochlear cells in different locations with multiple lights.

[0014] 1 is an embodiment of a cochlear implant device according to the present disclosure; FIG. 2 is an example of the configuration of an externally worn unit; FIG. 3 is an example of the configuration of an optical transmitter 30; FIG. 4 is an example of the configuration of a plurality of optical waveguides 60; FIG. 5 is an example of the configuration of a plurality of optical waveguides 60; FIG. 6 is an example of the configuration of a plurality of optical waveguides 60; FIG. 7 is an example of the configuration of a plurality of optical waveguides 60;

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0016] The configuration of a cochlear implant device according to this embodiment is shown in Fig. 1. In Fig. 1, A represents the ear, B represents the skull, C represents the inner ear, and D represents the cochlea. The cochlear implant device comprises an externally mounted unit 100 that is mounted outside the human body, and an internally mounted unit 200 that is mounted inside the human body. Fig. 1 shows an example in which the internally mounted unit 200 is mounted near ear A, and the internally mounted unit 200 is mounted outside the skull.

[0017] The internally mounted unit 200 includes a plurality of optical waveguides 60 of different lengths. The light emission positions in the plurality of optical waveguides 60 correspond to the sensitivity of the sound frequencies in the cochlea D. The externally mounted unit 100 includes an optical transmitter 30 that inputs light into the optical waveguides 60 corresponding to the sound frequencies. This allows the present disclosure to irradiate cochlear cells with light corresponding to the sound frequencies. Note that some of the plurality of optical waveguides 60 may be the same length.

[0018] It is desirable that the internally mounted unit 200 does not include any conductors. The optical waveguide 60 and its connecting members may all be made of synthetic resin such as plastic or glass. This is because the absence of conductors does not interfere with the use of MRI (Magnetic Resonance Imaging).

[0019] The configuration of the externally worn unit 100 is shown in Figure 2. In Figure 2, the externally worn unit 100 includes a microphone 10, a sound processor 20, and an optical transmitter 30. The microphone 10 converts collected sound into an electrical signal. The sound processor 20 analyzes the frequency components of the electrical signal from the microphone 10 to output the sound intensity for each sound frequency. The optical transmitter 30 directs light of an intensity corresponding to the sound intensity into an optical waveguide 60 corresponding to the sound frequency.

[0020] The configuration of the optical transmitter 30 is shown in Figure 3. The optical transmitter 30 acquires frequency information from the sound processor 20. The frequency information includes sound intensity information for each sound frequency. The signal processing unit 31 processes the frequency information from the sound processor 20 and instructs the optical emitting unit 32 corresponding to the sound frequency to emit light. The optical emitting unit 32 emits light in accordance with the instruction from the signal processing unit 31.

[0021] This disclosure illustrates an example including n optical transmitters 32. Each of the optical transmitters 32-1 to 32-n outputs light corresponding to the sound intensity to one of a plurality of optical waveguides 60 corresponding to the sound frequency. In FIG. 1, the optical waveguide 60 propagates signal light, extracts the signal light at an output corresponding to the optical waveguide 60, and irradiates the signal light onto cochlear cells. The signal light is output from the optical transmitter 32 corresponding to the sound frequency collected by the microphone 10 and has a light intensity corresponding to the sound intensity of that frequency. Therefore, this embodiment can irradiate cochlear cells corresponding to the sound frequency with light of a light intensity corresponding to the sound intensity. The light intensity of the optical transmitter 32 may be controlled by controlling the current value applied to the light source or by a variable attenuator.

[0022] Here, it is preferable that the light transmitter 32 intensity-modulates the signal light before outputting it. This is because cochlear cells are more sensitive to intensity-modulated light than to light with a constant intensity. It is desirable that the intensity modulation frequency of the light transmitter 32 be variable so that the intensity modulation frequency at which sensitivity is high can be adjusted. It is also desirable that the light transmitter 32 be able to vary the conversion coefficient from sound intensity to light intensity according to the sensitivity of the cochlear cells. The light transmitter 32 may use a light source with a fixed wavelength or a light source with a tunable wavelength. The intensity modulation of the signal light may be performed by a voltage applied to the light source or by an optical switch.

[0023] The distribution of sound frequency sensitivity within the cochlea D will now be explained. High frequency sensitivity is high near the entrance of the cochlea D, while low frequency sensitivity is high in the center. Although there are individual differences, for example, the highest sensitivity is 20 kHz near the entrance of the cochlea D, while 200 Hz is highest in the center. If the emission section is compatible with such sound frequencies, cochlear cells can be stimulated efficiently.

[0024] An example configuration of multiple optical waveguides 60 is shown in FIG. 4. The multiple optical waveguides 60 can be made of any means capable of individually propagating each signal light, such as a multi-core optical fiber, an optical fiber bundle, an optical fiber tape, or a silica-based planar lightwave circuit. Multiple signal lights (34-1 to 34-n) are input from the light input section of the optical waveguide 60 and output from the output section 61. Sensitivity to sound frequencies varies depending on the location within the cochlea D. Furthermore, the light transmitter 32 and the optical waveguides 60 connected thereto correspond to sound frequencies. Therefore, the lengths of the optical waveguides 60 are different, and the positions of the output sections 61 are different.

[0025] The emission position of the signal light from the emission portion 61 corresponds to the sensitivity of the sound frequency in the cochlea D. For example, the correspondence mapping between sound frequencies and the light emission portion 32 can be exemplified as follows: signal light 34-1 has a sound frequency of 200 Hz, signal light 34-2 has a sound frequency of 400 Hz, and signal light 34-n has a sound frequency of 20 kHz. The emission portion 61 of signal light 34-n is disposed near the entrance of the cochlea D. The emission portion 61 of signal light 34-1 is disposed near the center of the cochlea D. In this way, the signal lights emitted from the multiple emission portions 61 each stimulate cochlear cells located at positions in the cochlea D corresponding to the emission portions 61. Note that optical waveguides 60 of equal length may be provided, in which case the emission portions 61 may be disposed at the same positions in the cochlea D.

[0026] Because the position of the output unit 61 is determined for each optical waveguide 60, signal light can be accurately stimulated to cochlear cells corresponding to the sound frequency. Here, in the present disclosure, the wavelength of the signal light irradiated to the cochlear cells can be arbitrarily set. Therefore, the present disclosure makes it possible to comprehensively stimulate various wavelengths to address the sensitivity distribution of cochlear cells, which varies greatly from person to person. For example, a test may be conducted in advance to determine what sounds a cochlear implant device user can hear when signal light of a certain wavelength is emitted from a certain optical waveguide 60, and sound frequencies and wavelengths may be assigned to the light emitting unit 32 based on the test results.

[0027] The wavelength of the signal light can be changed by changing the type of light source in the light emitting unit 32 or by changing the temperature of the light source in the light emitting unit 32. However, since some output units 61 have wavelength dependency like diffraction gratings, the wavelength of the signal light is selected from a wavelength range suitable for the output unit 61.

[0028] The emission section 61 may have any one of the following configurations or a combination thereof: (i) A configuration in which the plurality of optical waveguides 60 are cut at an angle. (ii) A configuration in which an oblique diffraction grating is provided in any of the plurality of optical waveguides 60. (iii) A configuration in which a reflection filter is provided in any of the plurality of optical waveguides 60. (iv) A configuration in which one of the plurality of optical waveguides 60 is cut at an angle. (v) A configuration in which a Y-shaped waveguide is provided in any of the plurality of optical waveguides 60. (vi) A configuration in which one of the plurality of optical waveguides 60 is bent.

[0029] An example configuration of multiple optical waveguides 60 is shown in Figure 5. The emission section 61 can be realized, for example, by cutting the multiple optical waveguides 60 at an angle. By cutting the optical waveguides 60 at an angle, each optical waveguide 60 can emit signal light at a different location. Because the optical waveguides 60 are cut at an angle, the signal light emitted from the optical waveguides 60 is refracted due to the difference in refractive index between the optical waveguides 60 and air.

[0030] The configuration in which the multiple optical waveguides 60 are cut at an angle can be produced by polishing or etching the multiple optical waveguides 60. Depending on the angle at which the optical waveguides 60 are cut at an angle, it is possible to adjust the location of the signal light that can be extracted from each optical waveguide 60. Therefore, the angle at which the multiple optical waveguides 60 are cut at an angle may differ depending on the optical waveguide 60.

[0031] 6 shows an example of the configuration of multiple optical waveguides 60. The output section 61 may be fabricated by providing a diffraction grating 62 at a location of the multiple optical waveguides 60 from which the signal light is to be extracted. By providing the reflective diffraction grating 62 at an angle, the signal light is reflected obliquely, making it possible to extract the signal light from the optical waveguide 60.

[0032] The diffraction grating 62 can be fabricated by periodically irradiating it with a femtosecond laser. By using a photosensitive optical fiber for the optical waveguide 60, the diffraction grating 62 can also be fabricated by photolithography using ultraviolet light.

[0033] The diffraction grating 62 can be placed at any position on the optical waveguide 60, and the direction in which the signal light is extracted can also be adjusted. Therefore, the output unit 61 can be placed at a position suitable for the user of the cochlear implant device, and the signal light can be emitted in a direction suitable for the user of the cochlear implant device. In addition, the diffraction grating 62 can widen the range of wavelengths of the usable signal light.

[0034] An example configuration of multiple optical waveguides 60 is shown in Fig. 7. The output section 61 may be fabricated by installing a reflective filter 63 at a location of the multiple optical waveguides 60 from which the signal light is to be extracted. The reflective filter 63 can reflect the signal light, and by installing it at an angle, it is possible to extract the signal light from the optical waveguide 60. The reflective filter 63 can be fabricated using a dielectric multilayer film filter or the like.

[0035] When the output of the light emitting unit 32 is strong, a low reflectance of the reflection filter 63 does not pose a problem, so the optical waveguide 60 can also be manufactured by cutting it obliquely. For example, a multi-core optical fiber, a bundled optical fiber, or a tape optical fiber can be used, and each optical fiber can be cut obliquely at a desired length. By adopting such a configuration, it is possible to manufacture multiple optical waveguides 60 and emission units 61 at low cost.

[0036] An example configuration of multiple optical waveguides 60 is shown in Figure 8. The output section 61 can be fabricated by installing a Y-shaped waveguide 64 that branches the signal light at a location among the multiple optical waveguides 60 from which the signal light is to be extracted. By using the Y-shaped waveguide 64, it is possible to extract the signal light with high precision at the desired position in the optical waveguide 60. The Y-shaped waveguide 64 can be fabricated by drawing with a femtosecond laser or using a silica-based planar lightwave circuit.

[0037] The Y-shaped waveguide 64 can be placed at any position in the optical waveguide 60, and the direction in which the signal light is extracted can also be adjusted. Therefore, the emission unit 61 can be placed at a position suitable for the user of the cochlear implant device, and the signal light can be emitted in a direction suitable for the user of the cochlear implant device.

[0038] Since light leaks when the optical waveguide is bent sharply, a bent optical waveguide 65 may be used as shown in Figure 9. In this case, too, it is possible to fabricate the waveguide using a femtosecond laser or a silica-based planar lightwave circuit. Furthermore, since even a small amount of signal light leakage can stimulate cochlear cells, the bent optical waveguide 65 may be constructed by bending an optical fiber at the position of the output portion 61.

[0039] 10: Microphone 20: Sound processor 30: Optical transmitter 31: Signal processing unit 32: Optical transmission unit 60: Optical waveguide 61: Emission unit 62: Diffraction grating 63: Reflection filter 64: Y-shaped waveguide 100: Externally mounted unit 200: Internally mounted unit

Claims

1. A cochlear implant device comprising: a plurality of optical waveguides of different lengths; and an optical transmitter that directs light into the optical waveguides according to sound frequencies, wherein the light emission positions of the plurality of optical waveguides correspond to the sensitivity of the sound frequencies within the cochlea.

2. A cochlear implant device as described in claim 1, comprising: an external attachment unit that includes the optical transmitter and is attached outside the human body; and an internal attachment unit that includes the multiple optical waveguides and is attached inside the human body, wherein the internal attachment unit includes an emission unit that extracts light at different locations for each of the multiple optical waveguides.

3. The cochlear implant device of claim 2, wherein the externally worn unit comprises: a microphone that converts sound into an electrical signal; and a sound processor that outputs sound intensity for each sound frequency by analyzing the frequency components of the electrical signal from the microphone; and the optical transmitter outputs light having a light intensity corresponding to the sound intensity to an optical waveguide among the plurality of optical waveguides that corresponds to the sound frequency from the sound processor.

4. The cochlear implant device according to claim 2, wherein the output section includes a configuration in which the plurality of optical waveguides are cut obliquely.

5. The cochlear implant device according to claim 2, wherein the output section includes an oblique diffraction grating provided in one of the plurality of optical waveguides.

6. The cochlear implant device according to claim 2, wherein the output section includes a Y-shaped waveguide provided in one of the plurality of optical waveguides.

7. The cochlear implant device according to claim 2, wherein the output section includes a configuration in which any one of the plurality of optical waveguides is cut obliquely.

8. The cochlear implant device according to claim 2, wherein the output section includes a reflection filter provided in one of the plurality of optical waveguides.

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