Deafness

Deafness refers to the loss of a portion or all of the sense of hearing. This is the pathological definition and should not be confused with the term “Deaf” which is always capitalized and defines the culture of persons who cannot fully hear, do not view their deafness as a pathological or medical condition, and whose choice of communication is typically Sign Language. The term “deaf” (with a small “d”) refers to persons who have a hearing loss, and who do not consider themselves as culturally Deaf and frequently prefer spoken or manually coded language (i.e., Signed Exact English) and if they had no hearing loss they would be a part of the hearing world.

In general, there are three types of hearing loss: conductive, sensorineural, and mixed. Because of the development of the fetus and the young child, there are different subtypes or etiologies when considering pediatric and adult deafness. Conductive hearing loss is caused by any obstruction that limits external sound from traversing the external auditory canal, the tympanic membrane, the ossicles, and into the inner ear. Common acquired conductive obstacles of the external auditory canal encountered in clinical practice in adults include excessive buildup of cerumen (ear wax), external auditory canal infection with swelling and debris (otitis externa), fluid in the middle ear (both sterile and infected), and a loss of the ossicular mobility so that vibrations are not completely carried to the inner ear. Less commonly, tumors of the external auditory canal can cause conductive hearing loss. The most common cancerous tumor is squamous cell carcinoma, followed by basal cell carcinoma and melanoma. Tumors of bony origin include osteomata and exostoses and limit hearing by blocking sounds from reaching the tympanic membrane. Conductive hearing losses due to middle ear pathology include Eustachian tube dysfunction, development of a cholesteatoma; infection and fluid buildup with or without tympanic membrane perforation. Congenital malformations of the external auditory canal, tympanic membrane, and ossicles are also causes of conductive hearing loss.

In the pediatric population, congenital atresia (lack of development) of the external auricle, external canal, tympanic membranes, ossicles, and or the cochlea are causes of conductive hearing loss. Also, suppurative otitis media (infected) and otitis externa; dysfunctional tympanic membranes with or without perforation; and cholesteatoma all cause conductive hearing loss. A cholesteatoma is a growth of epithelium from the external canal migrating into the middle ear and [Page 475]causing a buildup of sloughed surface cells and chemicals which both block the hearing and destroy the inner ear. Malformations caused by trauma can cause any degree of conductive hearing loss depending on the obstructive sequelae.

Sensorineural hearing loss is caused by a deficient functioning of the inner ear cochlea and eighth cranial nerve (Vestibulocochlear nerve). Presbycussis (hearing loss of old age) is multifactorial and probably is caused by lifelong noise exposure, medications, and familial tendencies. In one series screening over 2,000 Medicare recipients, nearly 60 percent qualified as having sensorineural hearing loss. Another cause of sensorineural hearing loss is ototoxicity from multiple drugs, representative of which are the aminoglycosides (gentamicin, etc.); cancer chemotherapeutic agents (the worst being cisplatinum, then 5-FU and nitrogen mustard and bleomycin); aspirin; and antimalarial medications (chloroquine).

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