Conclusion: We studied the compound action potential (AP) recovery from adaptation (AP recovery) in idiopathic sensorineural hearing loss (iSSNHL). Abnormal AP recovery was demonstrated in 15 of 45 patients, consisting of increased recovery (iR) over the normal range in 11 ears and decreased recovery (dR) under the normal range in 4 ears. The mechanisms for occurrence and clinical significance of these phenomena are currently unknown.
Objectives: The purpose of this study was to investigate the pathologic features of AP recovery in iSSNHL.
Methods: Forty-five subjects with iSSNHL were enrolled and 18 normal-hearing subjects participated to assess the normal range of AP recovery. Equilevel paired clicks with inter-click interval from 5 to 100 ms were applied as acoustic stimuli.
Results: Eleven ears with iR and four ears with dR were found. The audiogram patterns of 11 iR and 4 dR ears exhibited 10 flat types, 3 high frequency loss types, and 2 low frequency loss types. Only 2 of 11 subjects with iR ears and 0 of 4 with dR ears complained of vertigo. No significant difference was observed in the comparison between AP threshold and hearing level of iR with those of normal recovery (nR) within the normal range.