Sudden sensorineural hearing loss (SSHL), or sudden deafness, is a rapid loss of hearing with onset over a period of < 72 hours. It is associated with ringing in the ears (tinnitus), dizziness, and a feeling of fullness or pressure in the ear. The estimated incidence of SSHL is between 5 and 20 per 100,000 persons per year but may be as high as 300 per 100,000 persons per year. The true incidence of SSHL is likely underestimated, since many who recover quickly never seek medical attention. There are multiple causes of SSHL which include viral infection, vascular impairment, autoimmune disease, and diseases of the inner ear. The suspected causes of SSHL are unknown in > 70% of cases and a direct causal link for SSHL has not yet been established.