Sudden Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is a rapid decrease in hearing, defined clinically as a loss of 30 decibels or more across three consecutive frequencies occurring within 72 hours. It is a medical emergency. Most cases affect only one ear and come on quickly, sometimes overnight or upon waking. The exact cause is often unknown (idiopathic), though proposed mechanisms include viral infection of the inner ear, vascular disruption to the cochlea, or autoimmune processes.

Symptoms can include a sudden reduction in hearing, a sensation of fullness in the ear, tinnitus, and sometimes dizziness. Immediate medical assessment is critical because treatment with systemic or intratympanic corticosteroids is most effective when started within the first days of onset. In Canada, sudden hearing loss requires urgent referral to an ENT specialist.

Without prompt treatment, the hearing loss may become permanent. Recovery varies: some individuals regain most or all of their hearing, while others retain a permanent deficit.