JPS6327016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an artificial hearing device, and more specifically, the process of converting a sound signal into an electrical signal in the cochlea is artificially compensated for by electrical stimulation to provide hearing aids for deaf people. It concerns an artificial hearing device that allows people to hear.

Artificial hearing devices apply electrical stimulation corresponding to sound signals to the auditory nerve, allowing people with severe inner ear hearing loss to hear sound.Whether the electrode that outputs the electrical stimulation is implanted in the cochlea or the auditory nerve, It is essential that the nerves to be stimulated remain.

Conventionally, as this type of device, the
I got what is shown in the figure. In the device shown in Fig. 1, a connector 1 is installed on the skin surface near the auricle E, and an external stimulator consisting of a microphone 2 and an amplifier 3 is directly connected to an electrode 4 implanted in the cochlea C via a conductive wire 5. It applies electrical stimulation to the With such a configuration, there was a problem in tissue compatibility between the skin and the material of the connector 1.

In the example shown in FIG. 2, a receiver 6 is implanted subcutaneously and connected to an electrode 4 through a conductor 5, and the receiver 6 is driven by an extracorporeal stimulation device consisting of a microphone 2, an amplifier 3, and a transmitter 7. It is configured to send signals using In this case, the receiver 6 is either implanted with a sensitive coil or implanted with a radio wave receiver, but the former has extremely poor sensitivity unless the coils inside and outside the skin are aligned with each other in the correct position. The major drawback is that the voltage generated in the coil and the signal waveform are unknown, so it is hardly put into practical use. the latter as a carrier wave
AM waves or FM waves are used, and although there is no need for strict alignment like the former, interference from other radio waves may occur.

The systems shown in Figures 1 and 2 above are both a combination of an external stimulator and an implanted part within the body, so they are often inconvenient in daily life.In contrast, the system shown in Figure 3 was proposed. That is, all the devices including the microphone 2, amplifier 3, and power battery 3a are implanted in the living body. Such a completely implantable structure is considered to be an ideal method because it does not require carrying an external device, is not cumbersome to wear, and has an excellent appearance.

However, an important problem with this system is the implantable microphone. That is, the electret microphone, which has traditionally been widely used in hearing aids, has excellent sensitivity and frequency characteristics, but has the following difficulties when used by implanting it in a living body.

(b) It is necessary to cover the entire device, including the diaphragm, with a biocompatible material without impairing the acoustic properties.

(b) It is difficult to further downsize while maintaining performance.

(c) Changes in performance and durability after implantation remain unresolved.

In contrast, a method using a piezoelectric film has been considered, but this method has the disadvantage that it is difficult to fix and is susceptible to change over time.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an artificial hearing device that functions stably and has desired characteristics by solving various problems in the conventional completely implantable structure using a microphone. The purpose is to

Another object of the present invention is to pick up the vibration of the malleus, which is connected to the eardrum, and convert it into an electrical signal by changing the structure of a conventional implanted microphone including a diaphragm. An object of the present invention is to provide an artificial hearing device configured to add an auditory nerve to an auditory nerve.

A further object of the present invention is to provide an artificial hearing device equipped with a malleus vibration pickup using a mechano-electric transducer made of piezoelectric ceramic.

Therefore, this invention is based on the premise that the eardrum and malleus are preserved in a normal or nearly normal state.

An embodiment of the present invention shown in the drawings will be described below.

In FIGS. 4 and 5, the support member 13 of the pick-up 11 is attached to the middle ear bone so that the needle-like member 12 provided at one end of the pick-up 11 made of piezoelectric ceramic comes into contact with the malleus H that connects to the eardrum T. It is properly fixed to the wall. Power supply battery 14, signal processing device 15
Both are implanted in a living body, and the output of the pickup 11 is connected to the signal processing device 15 via a lead wire 16.
The output of the signal processing device 15 is applied via a lead wire 17 to an electrode 18 implanted in the cochlea C and electrically connected to the auditory nerve.

As shown in FIG. 6, the pick-up 11 is a bent-shaped conversion element constructed by joining two ceramic piezoelectric elements 19a and 19b polarized in opposite directions in the thickness direction to form a so-called bimorph. The needle member 12 is a rigid body made of a biocompatible material such as sapphire or apatite. This needle-like member 1
2 plays an important role in contacting the surface of the malleus H and transmitting vibrations of the malleus H to the ceramic piezoelectric element, and considering that the surface of the malleus H is a curved surface, it is shaped like a needle. This allows it to faithfully follow the vibrations of the malleus H. A support member 13 provided at the other end of the pick-up 11 and securing the pick-up 11 to the middle ear bone wall is made of a biocompatible rigid body such as stainless steel. In addition, the lead wire 16, as well as other implanted lead wires, is made of polytetrafluoroethylene (PTFE).
Those covered with a biocompatible resin such as Furthermore, this porcelain piezoelectric element is provided with a covering 20 of silicone rubber or PTFE to prevent electrical leakage and deterioration of insulation.

Next, we will discuss the action and effect.

In the artificial hearing device configured as described above, the eardrum plays the role of the diaphragm of a conventional microphone, so there is no need to implant a new diaphragm, and the device can be made considerably smaller. Using a pickup 11 with a length of 7 mm, width of 1 mm, and thickness of 0.4 mm, we experimentally measured its frequency characteristics and sensitivity using a human temporal bone. characteristics were obtained. This can be easily measured by applying sound stimulation from the ear canal side and measuring the input sound pressure in front of the eardrum using a probe microphone, and then calculating the ratio of the output signal of the pickup 11 to this sound pressure. According to this measurement, a resonance point is seen around 2KHz, but the characteristics are relatively flat in other frequency regions. The resonance point of Pickup 11 itself is 4KHz
Since it is nearby, the resonance point has moved to a lower frequency due to contact with the malleus. Note that the sensitivity in this case was 0.9 mVX/94 dB at 1 KHz, and a sufficiently practical S/N ratio was obtained with this level of sensitivity. The pick-up 11 has the above-mentioned dimensions and can be attached to the head of the malleus with plenty of room. The problem is whether the implanted pick-up 11 will function stably over a long period of time. That is, the problems include the durability of the piezoelectric ceramic element itself, the influence of granulation growth after implantation, and the compatibility of the malleus H and the needle-like member 12. Pick-up 11 using piezoelectric ceramics
Regarding the strength and durability, it was confirmed that it functions stably for at least two years. The problem of granulation growth can be solved by covering the pick-up 11 with silicone. Regarding the compatibility between the malleus H and the needle-like member 12, by selecting a biocompatible material such as apatite for the needle-like member 12, fusion with the malleus can be expected. This problem can be solved by selecting 12 materials.

As described above, the implantation of the pickup 11 eliminates the obstacles that occur when implanting conventional electret microphones or piezoelectric film transducers, and makes it possible to establish a completely implanted structure.

[Brief explanation of the drawing]

1, 2, and 3 are schematic diagrams of a conventional device, FIG. 4 is a schematic diagram of an embodiment of the present invention, FIG. 5 is a partially enlarged view, and FIG. 6 is a schematic diagram of a conventional device. Similarly, FIG. 7 is a partially cutaway perspective view of the conversion element and a frequency characteristic diagram. 11... Pickup, 12... Needle member, 1
3...Support member, 14...Power battery, 15...Signal processing device, 16, 17...Lead wire, 18...
Electrode, 19a, 19b...Porcelain piezoelectric element, 20...
…Covered.

Claims (1)

[Scope of Claims] 1. An implantable pick-up that is made of a piezoelectric ceramic bimorph and has a needle-like member at one end that is to be brought into contact with the malleus, an implantable signal processing device that receives the output of the pick-up, and the signal An artificial hearing device comprising an implantable electrode to which the output of a processing device is applied and connected to an auditory nerve. 2. The artificial hearing device according to claim 1, wherein one end of the pick-up is provided with a needle-like member, and the other end of the pick-up is provided with a support member for fixing the pick-up in a living body. 3. The artificial hearing device according to claim 1, wherein the needle-like member is made of saphire. 4. The artificial hearing device according to claim 1, wherein the material of the needle member is apatite. 5. The artificial hearing device according to claim 1, wherein the pickup is covered with silicone rubber. 6. The artificial hearing device according to claim 1, wherein the pickup is covered with polytetrafluoroethylene. 7. The artificial hearing device according to claim 2, wherein the material of the support member is stainless steel.