Table 1. Diagnostic criteria for idiopathic sudden sensorineural hearing loss (ISSNHL)^*.

Main symptoms
1	Sudden onset of hearing loss
2	Sensorineural hearing loss, usually severe
3	Unknown cause
Accessory symptoms
1	May be accompanied by tinnitus
2	May be accompanied by vertigo, nausea, and/or vomiting without recurrent episodes
3	No cranial nerve symptoms (other than from cranial nerve XIII)

*ISSNHL was defined according to criteria described by the Sudden Deafness Research Committee of the Japanese Ministry of Health and Welfare [23]. Patients were diagnosed with definite ISSNHL if they presented with all the listed symptoms, or with probable ISSNHL if they presented mainly with only symptoms 1 and 2.