Hearing Loss
Hearing impairment may result from disease, injury, or developmental problems that affect the ear itself or any nervous pathways concerned with the sense of hearing. Sensorineural hearing loss results from damage to the eighth cranial nerve or to central auditory pathways. Heredity, toxins, exposure to loud noises, and the aging process are possible causes for this type of hearing loss. It may range from inability to hear certain frequencies of sound to a complete loss of hearing (deafness). People with extreme hearing loss that originates in the inner ear may benefit from a cochlear implant. This prosthesis stimulates the cochlear nerve directly, bypassing the receptor cells of the inner ear, and may allow the recipient to hear medium to loud sounds.
Conductive hearing loss results from blockage in sound transmission to the inner ear. Causes include obstruction, severe infection, or fixation of the middle ear ossicles. Often the conditions that cause conductive hearing loss can be treated successfully.
Otitis
Otitis is any inflammation of the ear. Otitis media refers to an infection that leads to the accumulation of fluid in the middle ear cavity. One cause is malfunction or obstruction of the eustachian tube, such as by allergy, enlarged adenoids, injury, or congenital abnormalities. Another cause is infection that spreads to the middle ear, most commonly from the upper respiratory tract. Continued infection may lead to accumulation of pus and perforation of the eardrum. Otitis media usually affects children under 5 years of age and may result in hearing loss. If untreated, the infection may spread to other regions of the ear and head. Treatment is with antibiotics. A tube also may be placed in the tympanic membrane to ventilate the middle ear cavity, a procedure called a myringotomy.
Otitis externa is inflammation of the external auditory canal. Infections in this region may be caused by a fungus or bacterium and are most common among those living in hot climates and among swimmers, leading to the alternate name, "swimmer's ear."
Otosclerosis
In otosclerosis, the bony structure of the inner ear deteriorates and then reforms into spongy bone tissue that may eventually harden. Most commonly, the stapes becomes fixed against the inner ear and is unable to vibrate, resulting in conductive hearing loss. The cause is unknown, but some cases are hereditary. The damaged bone can usually be removed surgically. In a stapedectomy, the stapes is removed and a prosthetic bone is inserted.
Ménière Disease
Ménière disease is a disorder that affects the inner ear. It seems to involve the production and circulation of the fluid that fills the inner ear, but the cause is unknown. The symptoms are vertigo (dizziness), hearing loss, pronounced tinnitus (ringing in the ears), and feeling of pressure in the ear. The course of the disease is uneven, and symptoms may become less severe with time. Ménière disease is treated with drugs to control nausea and dizziness, such as those used to treat motion sickness. In severe cases, the inner ear or part of the eighth cranial nerve may be destroyed surgically.
Acoustic Neuroma
An acoustic neuroma (also called a schwannoma or neurilemoma) is a tumor that arises from the neurilemma (sheath) of the eighth cranial nerve. As the tumor enlarges, it presses on surrounding nerves and interferes with blood supply. This leads to tinnitus, dizziness, and progressive hearing loss. Other symptoms develop as the tumor presses on the brainstem and other cranial nerves. Usually it is necessary to remove the tumor surgically.
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