Sudden sensorineural hearing loss (SSNHL) is defined by the American Academy of Otolaryngology guidelines as a hearing loss of ≥30 dB occurring across at least three contiguous frequencies within a 72-hour period. The condition affects 5-20 per 100,000 individuals annually, with peak incidence in the fifth and sixth decades. Patients typically present with awareness of hearing impairment upon awakening, frequently accompanied by aural fullness, tinnitus, and occasionally vertigo. Bilateral simultaneous SSNHL is exceedingly rare (1-2%) and warrants particularly thorough evaluation for systemic disease.
The etiology is identifiable in only 10-15% of cases, with the remainder classified as idiopathic. Identified causes include viral infections (mumps, measles, herpes simplex/zoster, cytomegalovirus), vascular events (thromboembolic, hemorrhagic, vasospasm), autoimmune disease (autoimmune inner ear disease, Cogan syndrome, vasculitis), neoplastic (vestibular schwannoma, leukemia), trauma (perilymph fistula, temporal bone fracture), ototoxicity, and metabolic disorders. The pathophysiology in idiopathic cases remains poorly understood, with leading theories including viral infection, cochlear vascular compromise, intracochlear membrane rupture, and immune-mediated injury, providing rationale for the empirical use of corticosteroids and antiviral agents.
Initial evaluation must include a thorough otologic history, physical examination, comprehensive audiometric testing (pure tone, speech audiometry, tympanometry), and tuning fork tests (Weber and Rinne) to confirm sensorineural rather than conductive loss. Urgent treatment with corticosteroids should not be delayed pending complete evaluation. MRI of the internal auditory canals with contrast is essential to exclude vestibular schwannoma (3-7% of SSNHL patients) and other retrocochlear pathology, ideally performed within 4 weeks. Standard treatment includes high-dose oral corticosteroids (prednisone 60 mg/day for 14 days with taper) initiated as early as possible, with intratympanic dexamethasone as primary or salvage therapy, particularly in patients with diabetes, peptic ulcer, or other contraindications to systemic steroids. Recovery rates approximate 50-65% with treatment, with prognosis influenced by age, severity at presentation, time to treatment, and audiogram pattern.