2.4 | Outcome evaluations
The pure-tone average of four frequencies (0.5, 1, 2, and 4 kHz) was calculated to compare the hearing outcome between two ASSR groups (WASSR and SBASSR groups). The initial PTA was performed within a month of onset of sudden hearing loss and before receiving steroid treatment. Hearing recovery was evaluated based on the result of the latest PTA. The hearing improved group was defined as patients whose final hearing level was better than 25 dB HL or whose hearing gain was more than 15 dB HL. Hearing gain was defined as the pure-tone average of four frequencies between the result of initial and last pure-tone thresholds.