Hearing impairment refers to all degrees of loss, from mild to profound. Deafness refers to more severe-to-profound loss. Hearing impairment can result from tumors, trauma, infection and other disorders.
Profound Deafness in Both Ears
Hearing loss in children can happen at birth in both ears, and adults can acquire deafness in both ears. When the patient cannot benefit from aggressive hearing aid amplification in both ears, cochlear implant surgery can be offered.
Courtesy of Cochlear Americas
A cochlear implant has an external part, shown here, and an internal part, implanted surgically. Headphone connection enables the rehabilitationist to hear what the patient hears.
We have performed more than 100 cochlear implant surgery procedures yearly, half of them in children. Most cases of hearing loss in children are not severe and allow the child to develop good vocabulary and grow up smoothly in the hearing world after surgery. Many adults who acquire deafness also can use the telephone well and converse in a normal fashion. Implanted hearing device technology is the fastest growing surgical field in otology-neurotology, and the new Center for Implantable Hearing Devices at Hillcrest Hospital offers state-of-the-art surgery and rehabilitation, using Cochlear Nucleus, Med-El and Advanced Bionics implants.
In addition, more patients are going for bilateral cochlear implants which significantly helps hearing in real world conditions. Hearing preservation cochlear implant surgery is also being developed.
Profound Deafness in One Ear
The bone-anchored device consists of an implanted titanium screw (A) and a removable speech processor (B).
A.) Implanted Titanium Screw
B.) Removable Speech Processor
Courtesy of Entific/Cochlear Americas
When one ear is deaf but the other is normal, especially after surgery for vestibular schwannoma (see below), hearing rehabilitation can be achieved through traditional CROS hearing aid or state-of-the-art bone-anchored hearing device (BAHA). Both systems pick up sound on the deaf side and transfer it to the normal side, the CROS aid usually by a wire or radio connection and BAHA by sound vibration traveling directly through the skull.
Patients who have converted from CROS to BAHA often say they prefer BAHA because the quality of sound is better and they do not need to wear an ear-level device on both sides. BAHA requires outpatient surgical placement of a titanium screw into the skull. After three months the screw incorporates well into the bone and an external sound processor can be attached and removed as desired. Wound breakdown, bleeding and infection are possible but very uncommon complications of surgery.
The stapes bone is fixed in position by surrounding bone so it cannot vibrate to conduct sound. The eardrum is raised, stapes removed, a small hole drilled, and prosthesis placed. Different prostheses require different techniques.
The stapes, a small stirrup-shaped bone in the middle ear, can become fixed to surrounding bone in one or both ears by a benign, progressive, often familial condition called otosclerosis. When hearing loss from otosclerosis interferes with quality of life, the patient can wear a hearing aid or have outpatient surgery through the ear canal to replace the stapes with a small prosthesis of platinum, titanium, Teflon or other material.
Although stapes surgery has been well described for more than 40 years, cases are less frequent now and technical demands of surgery require expert care from individuals who frequently perform microscopic ear surgery. A successful result, often with normal hearing, can be achieved in 90% of patients, with less than 1% chance of deafness in the operated ear. While dizziness, change of taste and numbness on the same side of the tongue can occur after surgery, these symptoms usually resolve spontaneously.
The malleus, incus and stapes can be fixed or destroyed by other disease such as infection. Such problems are usually repaired when infection is cured (see below). Occasionally the middle ear is explored in outpatient surgery to correct problems with these ossicles, either through the ear canal or through an incision behind the ear. Success varies with extent of disease. Overall 80% of patients have significant hearing improvement. Risk of deafness in the operated ear is less than 1%, and temporary change of taste and sensation on the same side of the tongue can occur but is temporary. Bilateral hearing loss from chronic infection also can be rehabilitated by a bone-anchored hearing device (BAHA).