Bone-anchored hearing aid, also known as a bone-anchored hearing device, is a type of hearing aid that is based on the conduction of sound to the inner ear through the bones of the skull. It is specifically designed for people who are suffering from hearing losses, single-sided deafness and those with mixed hearing losses that cannot wear ‘in-the-ear’ or ‘behind-the-ear’ hearing aids. These bone-anchored hearing aids are placed using minimally invasive surgery and have mild or minor complications.
Bone-anchored hearing aids use abutments that have been surgically implanted to transmit sound using bone conduction to the inner ear directly, bypassing the middle ear and external auditory canal. This makes them different from regular hearing aids. They are effective especially in cases where middle ear and ear canal problems may prevent sound vibrations and signals from getting into the inner ear through the normal acoustic pathways. They are useful for people who have chronic ear infections, chronic allergies, structural problems in the outer or middle ear and single-sided deafness.
It is recommended when there is continuous discharge from the ears. Normal hearing aids may worsen the condition by blocking the ear canal. Also in cases where there are structural deformities such as narrowing of the ear canal and absent or malformed external ear, a bone-anchored hearing aid is the solution because it transmits sound vibrations directly to the inner ear.
A bone-anchored hearing device consists of three major parts which are the titanium implant, a sound processor and an abutment (external connecting element). The titanium implant is surgically implanted into the skull with the small abutment which is exposed or placed outside the skin. The sound processor is placed on the abutment and its role is to transmit sound waves to the titanium prosthesis which in turn vibrates the skull and inner ear, thereby stimulating the nerve fibers of the inner ear and consequently, facilitating hearing.
The surgery is an outpatient procedure and is performed under local anesthesia in less than two hours. The removal of the implant can also be easily done, unlike most ear surgical procedures. It can increase hearing even in a noisy environment, localize sounds and improve understanding of speech and spoken language. It also causes the production of natural sounds with less distortion and feedback, unlike other conventional hearing aids.
Bone-anchored hearing aids are the most appropriate for people with unilateral hearing loss or single-sided sensorineural deafness by sending the sound from the bone of the skull of the deaf side to the inner ear of the hearing side thereby causing a total sound awareness.
Procedure: The bone at the back of the ear is exposed through a sharp incision and a hole is drilled. The hole is widened and the implant is inserted under generous cooling to minimize surgical trauma to the bone. A reduction of subcutaneous soft tissue may be done to decrease mobility between implant and skin in order to avoid inflammation of the penetrated site. The doctor will then adjust and fit the hearing processor to the patient’s hearing level three to six weeks after the surgical operation. This is done using a computer. Daily cleaning of the penetration site is required to avoid the risk of inflammation around the abutment. The surgery is usually not performed in children less than four years of age due to the thinness and softness of their skull/