What is the definition of sudden hearing loss?

Updated: Aug 28, 2019
  • Author: Neeraj N Mathur, MBBS, MS, DNB(ENT), MNAMS, FAMS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Definitions of sudden hearing loss have been based on severity, time course, audiometric criteria, and frequency spectrum of the loss. Abrupt as well as rapidly progressive losses have been included under a single definition of sudden hearing loss. Awakening with a hearing loss, hearing loss noted over a few days, selective low- or high-frequency loss, and distortions in speech perception have all been classified as sudden hearing losses. A commonly used criterion to qualify for this diagnosis is a sensorineural hearing loss of greater than 30 dB over 3 contiguous pure-tone frequencies occurring within 3 days' period. Fortunately, the vast majority of cases of sudden hearing loss are unilateral, and the prognosis for some recovery of hearing is good. Usually it presents as unilateral loss of hearing. An equal distribution of right- and left-sided cases should be expected; no greater risk for right-sided losses compared with left-sided losses seems to exist. Bilateral sudden hearing loss is rare, occurring in 1-2% of cases, and simultaneous bilateral involvement is very rare.

Sudden deafness or sudden sensorineural hearing loss (SNHL) has many possible etiologies.


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