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1Dr. Pradeep Shenoy, MD, FRCS, FACS, DLO, 2Stéphanie Bellemare-Gagnon, MPA, Aud (C)
1ENT & Neck Surgeon, Campbellton Regional Hospital, Campbellton, New Brunswick, Canada.
2Entendre Plus Hearing, Hearing and Balance Clinics.

Abstract
Sudden hearing loss—usually unilateral and rarely bilateral—can be associated with tinnitus and vertigo. In most cases it is idiopathic, although various explanations such as infective, vascular, and immune causes have been postulated. We have reviewed the literature and what follows is a survey of current research and suggested treatments for sudden hearing loss.
Key Words: sudden sensorineural hearing loss (SSNHL), tinnitus, pure tone audiogram (PTA), acoustic brainstem response audiometry (ABRA), viral neuritis, vascular insufficiency, oral steroids, intratympanic steroids, antiviral treatment, hyperbaric oxygen therapy (HBOT), MRI brain, acoustic neuroma.

Introduction
Sudden hearing loss is the loss of at least 30dB for three consecutive frequencies over the course of less than three days.1,2,4 The incidence of sudden hearing loss ranges from 5 to 20 per 100 000 individuals per year.1,2,3,4

According to the literature, unilateral sudden hearing loss represents between 95%1 and 98%3 of cases, and bilateral sudden hearing loss less than 5% of cases. Most cases are idiopathic and about 65% of them improve in the two weeks following initial loss.1

When a cause can be identified, it is most often viral.5 The remaining cases are linked to trauma, or otologic, vascular, hematologic, or neoplastic disease (see Table 1).

Table 1: Sudden Hearing Loss: Causes (%)

Causes

% of Cases3,4

Viral 12.8 to 13%
Otologic disease

4.7 to 5%

Trauma 4 to 4.2%
Vascular or hematologic 2.8 to 3%
Neoplastic 2 to 2.3%