Bone-Anchored Hearing Device
The bone-anchored hearing device (BAHA, for its original name, the bone-anchored hearing aid) is an implant system for children and adults who have conductive (middle ear) hearing loss and cannot be successfully fit with hearing aids. The implant is FDA-approved for use in individuals with single-sided deafness. A minor surgery is necessary to place portion of the system behind the ear. The implant is later coupled with an externally-worn speech processor. Also available is a new type of device, Sophono Alpha-1, that is implanted entirely under the skin and is not visible when the sound processor is removed.
How the BAHA Works
The BAHA works by direct stimulation of the cochlea (inner ear) through a small, surgical implant placed within the skull behind the ear. This implant is made of titanium, a material that permits the patient's own bone to integrate within the implant itself. After the implant has become fully integrated, the patient is able to wear a small, high-fidelity sound processor that can be snapped on and off. This processor transmits sounds to the internal implant which causes vibrations that directly stimulate the inner ear. As a result of this efficient stimulation, excellent hearing can be provided to people who do not have an ear canal and/or a normally functioning middle ear.
The majority of individuals who have conductive hearing loss can be fit with hearing aids or surgically treated with reconstruction of the middle ear structures that bring sound to the inner ear. Traditional hearing aids are referred to as air-conduction aids because they transmit sound through air and must be worn in the ear canal or attached to an ear mold placed within the canal.
The Best Candidates
There are individuals who are not ideal candidates for traditional surgery and cannot be successfully fit with air-conduction hearing aids. For example, many individuals born with aural atresia (lack of development of the ear canal) are not candidates for reconstructive surgery, nor can they wear air-conduction aids. Instead, they must wear a bone-conduction hearing aid that is placed behind the ear, adjacent to the mastoid bone. Bone-conduction hearing aids vibrate the skull in order to stimulate the inner ears. They provide distorted, poor quality sound and are uncomfortable to wear. The majority of patients with aural atresia are excellent candidates for the BAHA.
Individuals who have chronic infection of the ear, who cannot tolerate occlusion of the ear canal via hearing aid, are also potential candidates for the BAHA. Single-sided deafness is the latest indication for the BAHA. The implant is placed behind the deaf ear. Vibrations from the implant's response to sound stimulate the opposite, normal-hearing inner ear. The BAHA has been shown to be more effective for single-sided deafness than a cross hearing aid. Children with single-sided deafness having difficulty in school may benefit from this implant.