Bone Anchored Hearing Aid

The bone anchored hearing devices work by directly stimulating the inner ear through the bone. These devices have been in use since 1977 in Europe and was been FDA approved since 1996 for conductive and mixed hearing loss. The FDA approved its use for one-sided deafness in 2002. Baha is used to improve hearing in patients with chronic ear infections, congenital external auditory canal atresia (when the ear canal does not develop) or one-sided deafness who cannot benefit from regular hearing aids.

The Baha consists of three parts:

• The titanium implanted portion (small screw in the bone), which is similar to a dental implant
• An external abutment or magnet that connects with the screw) and
• The sound processor (hearing device) that clips onto the abutment or is held on with an external magnet through the skin.

The system works by taking the sound from the outside and transmitting it to the inner ear through the bone. This bypasses the ear canal and the middle ear. The titanium implant is placed during a minor surgical procedure and over time integrates with the bone behind the ear. The hearing device transmits sound vibrations through the titanium implant to the skull and the inner ear – where the hearing takes place.

The Baha is used to for people with conductive and mixed loss hearing loss with chronic infections of the ear canal or the middle ear (area behind the ear drum), people with a very narrow ear canal or an absent ear canal due to a congenital ear malformation, and people who are deaf in one ear.

People with chronic infections of the outer ear (ear canal) and the middle ear (area behind the ear drum) can benefit from Baha. Generally, people with these conditions have a chronic unpleasant drainage from their ears. The infection responds to conventional therapy with medications and surgery most of the time. However, sometimes it may recur and is deemed non-threatening. In these cases or when the infection recurs with the use of regular hearing aids that are placed in the ear canal, the Baha is a suitable choice for hearing improvement. Hearing aids that are placed in the ear canal may aggravate the infection by plugging the ear canal and contributing to increased humidity, which can allow bacteria to grow and cause infections. The advantage of the Baha sound processor is that it transmits the sound directly to the hearing organ without going through the ear canal and middle ear. Therefore, there is no occlusion of the ear canal that can aggravate infections. The Baha sound processor does not cause the occlusion effect, feedback and whistling seen with conventional hearing aids that are placed in the ear canal.

Congenital hearing losses caused by abnormalities or malformations of the ear canal or the middle ear can be treated with a Baha. Some of these patients do not have an ear canal or an ear canal that did not develop fully. A subset of these patients can be helped with reconstruction of the ear canal and the middle ear. The Baha sound processor is directly in contact with the bone of the skull through the titanium attachment allowing direct bone conduction (BC), the sound quality is significantly better than the bone conduction hearing aid, which was used in the past. There is no pressure on the skin with the use of the Baha which prevents the pain and headaches caused by the bone conduction hearing aid. Finally, the Baha can easily hide under the hair for a better cosmetic result.

Having two hearing ears has three main advantages.

• People with two hearing ears can understand speech better, especially in noisy situations, such as cocktail parties and restaurants, than those with one-sided hearing;
• People with two hearing ears can sit at a table and hear people on both sides without the need for turning the head;
• People with two hearing ears can tell the direction from which sound is coming.

The Baha device is an excellent, cosmetically appealing solution to this problem. Traditionally, patients would need to use two hearing aids, one on the deaf side to pick up the signal and another hearing aid in the hearing ear (to take the sound from the other ear and place it in the hearing ear). This type of hearing aid is called a CROS hearing aid. This means the patient needs to wear two large hearing aids which can be aesthetically displeasing.

When the Baha is placed on the deaf side, it picks up the sound and transmits it through the bone of the skull (bone conduction) to the inner ear on the hearing side. The normal ear hears sound through air conduction (sound traveling through the air in the ear canal and vibrating the ear drum). One-sided deafness patients with a Baha device can hear people sitting on their deaf side without the need to turn their head for listening. Recent studies have shown that patients prefer the sound and speech clarity achieved with the Baha when compared to the CROS and the unaided condition.

The procedure to place the Baha device is a short procedure that takes less than an hour. For adults, it can be done under local anesthesia, but for children, it is done under general anesthesia. It is done on an outpatient basis (patients go home the same day of the surgery).

It can take three to six months for the implant (younger patients need longer) to fully integrate into the bone in your skull. After it is fully integrated, it will then be paired with a sound processor that connects to the outside of the magnet or screw. The processor can be put on or taken off as you wish. It is not permanently attached to the implant. For magnet implants (Sophono or Baha Attract), the external (speech processor) is placed usually earlier than the 3 months after surgery.

There are three main options for bone anchored hearing aids.

• Cochlear™ Baha® Implant System – This device is held onto the head with a metal studabutment (Baha Connect), but there is also a version that uses a magnet (Baha Attract). It works well and is unobtrusive for patients with unilateral hearing loss.
• Sophono™ This device is held onto the head with a magnet, and another magnet is implanted into the skull. It performs best with speech frequencies and is designed so that the bone implant is not visible. It’s ideal for patients with less severe hearing loss at the inner ear level.
• Ponto System – This device is attached to a stud (abutment) located behind the ear. It has many programmable features and has a higher frequency response than the Sophono™.magnetic implants.

All patients are advised to undergo a thorough physical examination prior to the operation. Your doctor will want to know if you suffer from any condition that could impede your healing or ability to hear after the surgery is over. Medications that impede healing, e.g., steroid, immune suppressive drugs, etc. need to be stopped for a period before and after the surgery. The patient is asked to stop smoking as smoking increases the chance of losing the implant. We obtain an MRI in patients who will be getting a magnetic implant (Baha Attract or Sophono) to ensure no pathology is present in the temporal lobe on that side. The reason is that after the surgery, the magnet’s presence will prevent good imaging of that area of the brain.

The surgery is outpatient and the patient is seen about one week after surgery to check the wound. The patient will then return to see the audiologist a few months later to get the external device.

A new device by Med-El called BoneBridge recently (July 2018) obtained FDA approval in patients over the age of 12. This device has an active component under the skin which is driven by an outside speech processor and battery. The device has been in use since 2012 in Europe but was first placed in the U.S. in 2018. The external component of the device is similar to the Rondo cochlear implant speech processor.

Another recent device introduced in the U.S. is the AdHear device which is a bone conduction device that sticks to the back of the ear using stickers that are placed on the mastoid bone (bone behind the ear). The device then clips onto the special sticker.

One other bone conduction device that has come onto the U.S. market is the SoundArc device. This device uses the Baha speech processor and is attached to an arc-shaped device that is placed like backwards glasses on the head. The device is behind the ear and the arc goes between the two ears and the back of the head.