1 | INTRODUCTION
Sudden sensorineural hearing loss (SSNHL) is defined as a sensorineural hearing loss greater than or equal to 30 dB HL over at least three consecutive frequencies, occurring within 3 days.1Although the exact etiology is not well clarified, viral infection, vascular compromise, autoimmune processes, and labyrinthine membrane ruptures have been proposed as possible etiologies.1,2Given the ambiguity of the etiology of SSNHL, a number of different regiments have been used as therapy, including vasodilators, anticoagulants, corticosteroids, vitamins, plasma expanders, antiviral agents, diuretics, and hyperbaric oxygen.3-5 None of the treatment options have superiority on the others in randomized clinical trials,6 but systemic high dose steroid is currently the most widely accepted treatment for SSNHL.3-5
The natural history of SSNHL is still obscure. SSNHL may recover spontaneously in up to 65% of the patients.7,8However, nearly 40% of steroid-treated cases did not recover at all, or the hearing worsened over the treatment period.9 Thus, identification of prognostic factors is needed to predict the spontaneous recovery and risk for permanent or progressive hearing loss requiring maximal treatment. Many prognostic factors have been reported for SSNHL. Advanced age, presence of vertigo at onset, more severe initial hearing loss, descending type of audiogram, cardiovascular risk factors such as diabetes were shown to be negatively correlated with recovery.10 In recent years, several authors have reported on the clinical application of electrophysiologic hearing tests such as otoacoustic emissions (OAEs) or auditory brainstem response (ABR) in patients with SSNHL.11-14 However, there has been no report on the predictive value of auditory steady-state response (ASSR) in the hearing prognosis of SSNHL. The purpose of the present study was to investigate whether ASSR can be a prognostic indicator of hearing outcome in patients with SSNHL.