References Cited

U.S. PATENT DOCUMENTS

4,498,461 21 1985 Hakansson

4,612,915 A 9/ 1986 Hough et al .

7,664,277 B2 2/ 2010 Abolfathi et al.

8,150,075 B2 4/ 2012 Abolfathi et al.

8,246,532 B2 8/ 2012 Ball et al.

2003/0045283 Al 3/ 2003 Hagedoorn

7,257,372 B2 8/ 2007 Kaltenbach et al.

8,666,314 B2 3/ 2014 Lotter et al.

FIELD OF THE INVENTION

The present invention relates to implantable medical devices that improves hearing using bone conduction for patients with conductive and mixed hearing loss.

BACKGROUND OF THE INVENTION

Hearing process for a healthy person consists of 3 stages. In the first stage, sound travels in air, enters the auditory canal and vibrates the Tympanic Membrane. In the second stage, the ossicular chain bones transmit this vibration to the inner ear. Finally in the last stage, fluid of the cochlea vibrates due to the transmitted vibration and ultimately sensory hair cells send impulses along the auditory nerve to the brain.

Hearing problems can occur in any stage and age. The hearing problems are categorized according to the stage of the problem. Conductive hearing loss occurs when hearing loss is due to the problems with first two stages. Sensorineural hearing loss occurs when hearing loss is due to the problems with last stage. Furthermore, there can be mixed hearing loss where a combination of hearing stages has problems. There are various reasons and treatments for each type of hearing loss. The first treatment option is the conventional hearing aids which are widely available. Conventional hearing aids are acoustic type hearing aids worn in the auditory canal which are basically amplifiers that amplify the input sound received by a microphone and transmit the amplified sound to the Tympanic Membrane by a speaker. However, if the patient has conductive type hearing loss due to any reason, conventional hearing aids cannot be used.

Bone conduction method which is the basic principle of this present invention is especially effective for conductive type hearing loss. Bone Conduction Implants (BCIs) are implantable medical devices for the treatment of hearing losses in patients who cannot use or do not receive any improvement with conventional hearing aids. BCIs are basically vibration sources that use the bone conduction path to transmit sound directly to the inner ear bypassing the outer and middle ear. Since the first introduction of BCIs they have evolved in their external design and functionality. Even the surgical technique has undergone several modifications. Today, basically they are available as percutaneous and transcutaneous devices from several brands such as Cochlear, Medel, Sophono, Oticon etc. Furthermore, the BCIs are not limited to the skull mounted devices but can also be dental implants such as described in Us. Pat. No. 7,664,277 and 8,150,075.

SUMMARY OF THE INVENTION

The present invention is a transcutaneous design where the vibration generator is attached to the mastoid area of the temporal bone. This invention aims to reduce the external components for better cosmetic appearance and ease of use. The subcutaneous components include a wireless receiver (such as Bluetooth), a rechargeable battery, a Digital to Analog Converter (DAC), an AC-DC converter and some regulating electronics. The exterior components of the invention include a microphone and a sound processor with a wireless transmitter which is powered by a standard hearing aid battery. These components can be on any location of the patient as long as the microphone is free to receive ambient sound. In an alternative configuration the sound processor can be a smart phone and the microphone can be equipped with a wireless transmitter which will allow more freedom for attachment on the user. Furthermore, this invention allows the user to receive any digital audio information from the wireless interface such as music, text messages, e-mails etc. if coupled to a smart phone. The distinguishing property of the present invention is that there will be no external accessories on the head of the patient.

The vibration generator can be an electrodynamic shaker or a piezoelectric shaker where each one has completely different internal designs to generate the necessary vibration levels for bone conduction hearing.

The electrodynamic shaker can consist of a moveable coil or magnet where each configuration has different advantages and disadvantages. The electrodynamic shaker has inner and outer pole pieces, a coil and a chassis. The electrodynamic shaker also incorporates a piezoelectric energy harvesting design which charges the rechargeable battery during operation of the BCI which significantly extends the battery life. In order to minimize the current consumption, all of the electronic components are selected or designed as ultra low power. Furthermore, the shaker is optimized magnetically and mechanically to consume ultra low power while generating the necessary vibration levels.

The piezoelectric shaker has much smaller dimensions compared to the electrodynamic shaker but consumes more power in operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a lateral view of the hearing aid device showing the subcutaneous components that are implanted to the patient. Figure 2 is one of the proposed system structure showing components of the hearing aid device with external components.

Figure 3 is the cross sectional view of the electrodynamic shaker which is one of the alternatives for the vibration generator.

DETAILED DESCRIPTION OF THE INVENTION

The present invention consists of 6 components which can be given as

1 - Microphone

2- Sound Processor

3- Wireless transmitter and receiver

4- Electronic conditioning module (ECM)

5- Rechargeable battery

6- Vibration generator including energy harvesting system

The complete system consisting of these components is shown in Figure 3. The details of each of the component will be separately discussed in the following sections.

1 - Microphone: The microphone that will be used in this invention will be placed on an appropriate position of the patient. Therefore, there are no specific requirements for this component. The only major requirement is that the power consumption has to be low for long term usage.

2- Sound Processor: The sound processor includes a powerful digital signal processor (DSP) in order to process the data received from the microphone for noise suppression and boosting the signal. Various commercially available DSP chips are present where all of them can be used without any constraint.

3- Wireless transmitter and receiver: The wireless transmitter in this invention is used to transmit the conditioned sound signal to the receiver implanted to the patient. The transmitter and receiver must be ultra low power and show very little delay. The wireless transmission can use a Bluetooth network where similar wireless designs were introduced in Us. Pat. No. 2003/0045283, Us. Pat. No. 7,257,372 and Us. Pat. No. 8,666,314.

4- Electronic conditioning module (ECM): The ECM is implanted to the patient where digital to analog conversion takes place. Besides digital to analog conversion, many signal conditioning modules are present in the component.

5- Rechargeable battery: The rechargeable battery used in this invention must have high capacity and long cycle life in a very small size which is hermetically encapsulated with biocompatible material. The battery does not have to be placed in the temporal region where it can be placed at a subcutaneous position close to the temporal region such as the cervical or the precardiac region. The cables from the battery are routed from tunnels underneath the skin. The cables will be placed in biocompatible silicone elastomer body. The recharging of the battery is performed with wireless charging technology which uses a receiver coil that is implanted transcutaneously to the patient.

6- Vibration generator including energy harvesting system: The vibration generator is the main component of this invention. This component in this present invention is an electrodynamic shaker; it could also be a piezoelectric shaker. Electrodynamic shakers (ES) are basically voice coils consisting of a permanent magnet and coil. The moving element can be the coil or the magnet depending on the design requirements. The moving element is usually suspended by an elastic membrane. In this present invention the magnet is suspended whereas the coil is fixed to the outer shell. This also simplifies the design of the ES because we don't have any moving cables of the coil. The design of the ES starts with the force requirement and is formed by constructing the magnetic circuit. In order to have an ultra low power ES, the magnetic circuit optimization is crucial. The magnetic circuit includes two center pole pieces, one above and one below the magnet, and the outer shell which is also a ferromagnetic material.

Furthermore, the design of the elastic membrane is the main structural amplifier that has to be studied carefully considering the frequency bandwidth of amplification. The shaker is encapsulated with biocompatible materials such as titanium. The mastoid bone thickness varies greatly from patient to patient. This is the major handicap for the implantation of the ES. In order to overcome this problem, a special attachment design is made. Furthermore, this attachment design is also used as a structural amplifier which further increases the vibration gain.

The design also incorporates a piezoelectric energy harvesting multilayer disc that continuously supplies the battery during the operation of the ES. The mass of the moving elements (magnet and center pole pieces) that are also the compression mass of the energy harvester are optimized for maximum energy generation. An AC-DC regulator is used at the output of the energy harvester for the conditioning of the output signal.

Principal Advantages Over Prior Devices

In this section the principal advantages of the present invention over prior devices will be discussed by giving brief introductions about them.

Bone Anchored Hearing Aid (BAHA):

The early system designed by Hakansson described in Us. Pat. No. 4,498,461 operates by the same principle. A surgical screw is attached to the mastoid of the patient. The ES is attached to this screw where the ES stays on the exterior portion of the patient. All components of the BCI can be removed at any time leaving just the screw on the patient. This design is a percutaneous design which is still widely used. Aside from the cosmetic disadvantages, it is difficult to prevent infection as the screw is protruding from the skin. Recent transcutaneous versions (BAHA Attract) of this device use magnetic transmission to excite the mastoid where a magnet is placed on the mastoid and an ES is placed on the skin. A very similar working principle was introduced by Xomed Inc. given in Us. Pat. No. 4,612,915. However, this design has also some basic disadvantages compared to the present invention. The ES of the present invention has direct contact to the mastoid which gives much higher gains. Furthermore, present invention does not continuously squeeze the skin between the ES and magnet as the BAHA Attract does.

Vibrant Sound Bridge:

The recent system designed by Ball described in Us. Pat. No. 8,246,532 works in a similar fashion. This time the ES is implanted into the mastoid along with regulating electronics and a receiver coil. The receiver coil receives both power and signal from the external unit which contains the sound processor and microphone. The size of the ES makes the implantation procedure more invasive compared to the BAHA devices. Furthemiore, the external unit is a cosmetic disadvantage of the device.

The present invention overcomes mentioned problems by the special attachment design which reduces the penetration of the ES to the mastoid bone. Furthermore, the present invention does not have any external unit which greatly improves the cosmetic appearance. The present invention uses wireless data transfer (e.g. Bluetooth) which gives great flexibility for the placement of the microphone and sound processor which is not limited by the head of the patient. Finally, the energy harvesting system in the ES improves the battery life tremendously.