Chapter 6: Hearing Loss & Dizziness

HEARING LOSS

General Considerations

Approximately 28 million Americans experience some degree of hearing loss. Hearing loss is divided into two types: conductive and sensorineural. Conditions that include both types are classified as mixed hearing loss. Pathologies limited to the external auditory canal or the middle ear result in conductive hearing loss. Lesions involving the cochlea or the retrocochlear structures (cranial nerve [CN] VIII, or the central auditory pathways) produce sensorineural hearing loss.

Clinical Findings

A. Symptoms and Signs

Hearing loss can be congenital or acquired. Patients with congenital hearing loss may have other associated congenital malformations. Delay in speech acquisition is common and is often the presenting complaint in children with undiagnosed cases of hearing loss. Also, a family history of hearing loss may be present.

Acquired hearing loss may be sudden or insidious in onset. Ear pain, if present, usually reflects an acute infection involving the external or the middle ear. Otorrhea is common in patients with chronic middle ear infections. Painless, progressive hearing loss, without a history of previous ear infection or surgery, may be secondary to otosclerosis or pathologies involving the inner ear. Associated aural fullness, tinnitus, or vertigo is common in patients with inner ear pathologies. Sudden onset hearing loss should be evaluated immediately to rule out the presence of sensorineural hearing loss.

Patients with hearing loss should undergo a complete examination of the head and neck. Impacted cerumen, if present, should be removed to allow for better visualization of the tympanic membrane. Erythema and edema of the external auditory canal are signs of acute otitis externa. The status of the tympanic membrane reflects the status of the middle ear. An erythematous, bulging tympanic membrane is indicative of an acute infection in the middle ear. Otorrhea in association with an abnormal appearance of the tympanic membrane suggests a possible perforation. Patients with dull tympanic membranes should be assessed for the presence of fluid in the middle ear. Retraction of the tympanic membrane with no signs of acute infection could be a sign of eustachian tube dysfunction. The ear examination is usually normal in patients with sensorineural hearing loss.

Tuning-fork testing, using a 256-Hz or 512-Hz tuning fork, can sometimes differentiate conductive from sensorineural hearing loss. Sound presented to the patient by air conduction is perceived as louder than bone conduction (positive Rinne test) in patients with normal hearing or sensorineural hearing loss. Patients with conductive hearing loss, on the other hand, perceive bone conduction as louder than air conduction (negative Rinne test). When the tuning fork is placed at the center of the forehead (Weber test), the sound lateralizes to the better ...