2.2 | Study design and patients
We retrospectively reviewed the medical records of patients who admitted to [Blinded for review] University Hospital for SSNHL between August 2013 and December 2018. Inclusion criteria for the study included 1) unilateral SSNHL with a minimum 30 dB HL in three continuous octaves that had occurred within a course of 3 days; 2) patients who performed ASSR test withing 2 days after initial audiogram; 3) patients who received systemic high dose steroid therapy within one month after onset; 4) patients who had initial and follow-up audiogram. Exclusion criteria included 1) a history of previous SSNHL; 2) any recognized cause of SSNHL such as Meniere’s disease, active viral infection, vestibular schwannoma, or congenital anomalies; 3) a history of chronic otitis media or otologic surgery.
Age, sex, side of affected ear, the presence of dizziness, ear fullness, and dizziness, and comorbid diabetes mellitus (DM) were also collected. All enrolled patients received systemic steroid therapy and/or intratympanic dexamethasone (ITD) injection within one month after onset. Systemic steroid therapy was considered the first-line treatment and comprised a single morning dose of oral steroid each day for 2 weeks (48 mg of methylprednisolone for 4 days, followed by a taper of 8 mg every 2 days). ITD injection was administered as a salvage therapy for patients who did not exhibit recovery after an initial one week of systemic steroid treatment. ITD injections were performed 3–5 times with dexamethasone (4 mg/ml) within 2 weeks of diagnosis. No additional treatment, including antiviral agents, prostaglandin, vitamins, or hyperbaric oxygen therapy were used as second line treatments.
Patients were divided into two groups according to the difference of hearing thresholds between pure-tone audiometry (PTA) and ASSR ([ASSR threshold – pure-tone threshold] at 0.5, 1, 2, and 4 kHz). Because the ASSR mostly could not measure the hearing thresholds in profound hearing loss,15 subjects who had more than 90 dB HL hearing thresholds were excluded in grouping. If the patients had a ≥ 15 dB HL ASSR predicted thresholds compared to pure-tone threshold ([ASSR predicted threshold – pure-tone threshold] ≥ 15 dB HL) at least one frequency, it defined as a worse ASSR (WASSR) group. If the patients had a < 15dB of ASSR predicted thresholds compared to pure-tone threshold thresholds ([ASSR predicted threshold – pure-tone threshold] < 15 dB HL) at all frequencies, it defined as a similar or better ASSR (SBASSR) group.