Goroll_Primary Care Medicine, 8e

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SECTION XIV Ear, Nose, and Throat Problems

Hereditary Sensorineural Hearing Loss Hereditary sensorineural hearing loss is generally bilaterally symmetric. Many syndromes have been identified in which hereditary hearing loss is associated with anomalies in other organ systems, but nonsyndromic hereditary hearing loss is also recognized. Among persons with isolated (“nonsyndromic”) hearing loss, there is a high frequency of mutations in the gene GJB2 , which codes for the synthesis of connexin . Mutations in this gene are found not only among congenitally nonsyndromic deaf children, who are usually homozygous for the mutation, but also in the carrier state among adults with late-onset isolated hearing loss. The frequency can be as high as 3% across many different populations. It is suspected that the carrier state may predispose to hearing loss later in life and account for some, if not many, cases of age-related hearing loss that are commonly encountered. More work is needed to confirm these intrigu ing and potentially important findings. Although screening for mutations of this gene is not difficult, the degree of hearing loss and its time of onset cannot yet be predicted. A small number of patients may exhibit a unilateral, genetically programmed sen sorineural hearing loss later in life. Family history is important. Injury Injury to the inner ear or cochlear nerve may produce an asym metric sensorineural hearing loss. Skull fracture, meningitis, and mumps are major etiologic factors. Trauma may also cause conductive hearing loss, for example, hemotympanum, tym panic membrane perforation, or ossicular dislocation. Other Etiologies Congenital Syphilis. Congenital syphilis may produce adult onset sensorineural hearing loss. One or both ears may be affected; the course can be variable, with remissions and exacer bations. Vertigo is sometimes present as well, producing a symp tom complex mimicking Ménière disease. Multiple Sclerosis. Multiple sclerosis should be considered when a young woman shows discrimination scores reduced out of proportion to the pure-tone thresholds (similar to the pattern seen with acoustic neuromas). The site of the lesion is retroco chlear (often in the brainstem), and there may be an associated history of optic neuritis and/or vertigo. Perilymph Leaks or Fistulas. Perilymph leaks or fistulas may cause hearing loss, with or without vertigo, in individuals who have had inner ear surgery (e.g., stapedectomy), have sustained head trauma, or have congenital inner ear anomalies. The round and/or oval windows may be involved, and it is theorized that there is intracochlear membrane rupture as well. Surgical repair may be required. Expeditious referral to an otolaryngologist should be considered. Superior Semicircular Canal Dehiscence Syndrome. Superior semicircular canal dehiscence syndrome is a less common but increasingly recognized cause of hearing loss. Due to a thin ning or complete absence of the temporal bone that overlies the superior semicircular canal, patients may experience hearing loss that appears conductive in nature, commonly accompanied by vertigo, and paradoxically, hyperacusis. Surgical repair may be required. DIFFERENTIAL DIAGNOSIS (3) The causes of hearing loss can be grouped according to whether the problem is conductive or sensorineural (Table 212-1). The categorization is of practical use because the conductive defects lend themselves to correction in many instances. The causes of sudden sensorineural hearing loss are particularly important to consider (Table 212-2).

Table 212-1 C ommon and Important Causes of Impaired Hearing Conductive Sensorineural Impacted cerumen Presbycusis Foreign body

Noise-induced deafness

Occlusive edema of auditory canal

Drugs (aminoglycosides, loop diuretics, quinidine, aspirin)

Perforation of tympanic membrane Ménière disease Chronic otitis media Acoustic neuroma Serous otitis media

Hypothyroidism (mild loss) Idiopathic sudden deafness

External otitis Otosclerosis

Congenital syphilis

Exostoses

Diabetes

Developmental defects

Perilymph leak Multiple sclerosis Folate deficiency

Glomus tumors Superior semicircular canal dehiscence syndrome

WORKUP (3,11–16) History

Evaluation of the patient with hearing loss should focus on detection of the site of lesion. This search is aided by identify ing whether the impairment is conductive or sensorineural. History is of substantial importance. It is worth trying to find out the sounds or situations in which the patient has most trou ble hearing. Difficulty understanding spoken words suggests sensorineural hearing loss. Inquiry into drug use is essential, focusing on aminoglycosides, quinine derivatives, salicylates,

Table 212-2 I mportant Causes of Acute Sensorineural Hearing Loss

Predominantly Unilateral Retrocochlear disorders (1% of cases) Vestibular schwannoma Demyelinating disease Stroke Cochlear disease (15%–30% of cases) Ménière disease Trauma Autoimmune disease Syphilis Lyme disease Perilymphatic fistula Idiopathic (70%–85% of cases) Bilateral (rare) Psychiatric (“functional”) disorder Paraneoplastic syndrome Encephalitis Spinal tap Intracranial surgery

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Adapted from Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg 2012;146: S1–S35. Copyright © 2011, Official Journal of the American Academy of Otolaryngology—Head and Neck Surgery Foundation.