Hearing Loss

Hearing loss results from an interruption in the transmission of sound or subsequent nerve impulses in one or more areas of the ear. Recognition and treatment of hearing loss are imperative; unrecognized or untreated hearing loss may result in severe psychosocial ramifications in both adults and children. In the elderly population, hearing loss may lead to social withdrawal and depression. In the pediatric population, hearing loss may cause speech or cognitive delays. Hearing loss also has significant safety implications when it interferes with awareness of warning sounds (e.g., car horns, sirens, fire alarms). The four types of hearing loss follow:

1. Conductive hearing loss (CHL) occurs when there is a failure of normal propagation of acoustic energy through the conducting portions of the ear, which include the external auditory canal and the middle ear.

2. Sensorineural hearing loss (SNHL) occurs from dysfunction of the inner ear, which may be caused by a failure of the generation of nerve signals in the cochlea by the cochlear hair cells or propagation of electrical signals along the cochlear division of the eighth cranial nerve.

3. Mixed hearing loss (MHL) occurs when hearing loss results from both CHL and SNHL.

4. Central hearing loss can result from ischemic or traumatic brain injuries.

Hearing loss may be subclassified according to whether it is acquired or congenital. Hearing loss is further classified based on its severity (mild, moderate, severe, profound), sid-edness (right, left, bilateral), stability (stable, progressive, fluctuating), and cause.

Evaluation includes noting the onset and duration of the hearing loss, any inciting events, the subjective severity of the hearing loss, and any psychosocial impact. Associated ear symptoms, medical history, and a history of ototoxic medication exposure are also important. Although history and examination provide clues to the etiology of the hearing loss, comprehensive audiometric evaluation is essential to making a diagnosis. Box 19-6 lists the most common types of CHL and SNHL.

Hearing Aids Inside Out

Hearing Aids Inside Out

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