Bone-Anchored Hearing Aids

The BAHA is a semi-implantable percutaneous bone conduction hearing device coupled to the skull by an osseointegrated titanium implant. It has been used since 1977, and was cleared by the FDA in 1996 as a treatment for conductive and mixed hearing losses in the United States. In 2002, the FDA approved its use for the treatment of unilateral sensorineural hearing loss. Today, there are over 75,000 people with a BAHA implant

BAHA is used to help people with chronic ear infections, congenital external auditory canal atresia and single sided deafness who cannot benefit from conventional hearing aids. The system is surgically implanted and allows sound to be conducted through the bone rather than via the middle ear – a process known as direct bone conduction.

A BAHA consists of three parts: a titanium implant, an external abutment and a sound processor. The system works by enhancing natural bone transmission as a pathway for sound to travel to the inner ear, bypassing the external auditory canal and middle ear. The titanium implant is placed during a short surgical procedure and over time naturally integrates with the skull bone. For hearing, the sound processor transmits sound vibrations through the external abutment to the titanium implant. The vibrating implant sets up vibrations within the skull and inner ear that finally stimulate the nerve fibers of the inner ear, allowing hearing.

The BAHA is used to rehabilitate people with conductive and mixed loss hearing impairment. This includes people with chronic infection of the ear canal, people with an absent or a very narrow ear canal as a result of a congenital ear malformation, infection, or surgery, and people with a single sided hearing loss as a result of sudden hearing loss or surgery for a vestibular schwannoma (a tumor of the balance and hearing nerves).

Chronic ear infection treatment

A BAHA may be suitable for people with a conductive or mixed hearing impairment caused by a chronic infection of the middle or outer ear that results in a persistent and unpleasant discharge. The first goal, of course, is to manage the infection. In rare cases, chronic infections fail to respond to treatment, but are determined to be non-threatening. In other cases, infections respond to treatment, but recur with use of a conventional in-the-canal hearing aid or earmold. When a hearing aid or earmold is placed in a susceptible ear canal, a chronic or recurrent infection may be aggravated resulting in excessive humidity and lack of drainage. In these cases, the BAHA may be a good solution for hearing rehabilitation.

The BAHA sound processor transmits sound directly to the hearing nerve without involving the ear canal and there is no occlusion of the ear canal to aggravate infection. A BAHA sound processor offers sound quality at least as good as a conventional air conduction device, as it uses the person’s natural ability to hear via bone conduction. For those who need high levels of amplification, problems related to feedback and discomfort are usually resolved.

Congenital conductive hearing loss

Congenital conductive hearing loss caused by a malformation of the middle or external ear resulting in a missing or incomplete ear canal (external auditory canal atresia) are effectively managed with a BAHA. Traditionally, people with this type of hearing loss have been offered an old-fashioned bone conducting hearing aid which were held on the head using a steel spring headband or included in the frame of a pair of glasses.

Traditional bone conductors have several disadvantages:

• The sound quality is poor as the skin acts as a barrier for the sound to travel to the inner ear.
• They are uncomfortable – patients complain of pain and headaches due to the constant pressure of the headband.
• They are also cumbersome, obtrusive and insecure. 

The BAHA system can be a real solution for people with this type of conductive impairment. The BAHA sound processor is directly integrated to the skull bone. Because of this direct interface, the BAHA offers significantly better sound quality than that of a traditional bone conductor. The BAHA sound processor works without pressure on the skin avoiding the headaches and soreness associated with the conventional bone conductor and offers excellent wearing comfort and a better aesthetic result.

Single-sided deafness

One ear does not provide adequate hearing in many situations. Patients with severe hearing loss on one side, but normal hearing in the other ear have difficulty understanding speech in background noise (such as group conversations and restaurants) and determining which direction sound comes from. Unilateral deafness can result from viral infections, trauma, vestibular schwannomaand other ear tumors, and ear surgery.

Until recently, the best available approach for providing help in this situation has been the CROS (contralateral routing of signal) hearing aid. This technique utilized hearing aid microphones worn in both ears and routed sound from the deaf ear to the hearing ear. Unfortunately, most patients were unsatisfied with this system. Common complaints include the cosmetic appearance and discomfort of the headband, and the use of a hearing aid mold in the good ear. Most patients felt the benefit from the device is not worth the disadvantages.

The BAHA, now a FDA cleared solution for unilateral deafness, provides a completely unique benefit. The BAHA device is placed on the side of the deaf ear, transferring sound through bone conduction, and stimulating the cochlea of the normal hearing ear. The BAHA effectively transmits sounds from the bad side into the normal ear resulting in a sensation of hearing from a deaf ear. Stereo hearing results in improved understanding of speech, especially in background noise and aids in the localization of sound.

The BAHA offers significant advantages to the traditional CROS hearing aid. The device is placed behind the ear leaving the canal open. It may be worn under the hair and may not be perceptible to others. Because it is held in place and directly integrated with the skull bone, there is no need for a head band and pressure against the skin of the head. In recent clinical trials patients prefer the sound and speech clarity achieved with the BAHA verses the CROS or unaided condition.