Temporal Resolution and Speech Recognition Ability of Patients with Retrocochlear Auditory Dysfunction

Abstract

ObjectiveTo study the effect of temporal resolution measured by gap detection tasks on the speech recognition ability of patients with retrocochlear auditory dysfunction.Material and MethodsThe gap detection thresholds (GDTs) for dichotic stimuli were measured for 23 patients with retrocochlear auditory dysfunction confirmed by abnormal auditory brainstem responses the relationship between GDTs and maximum speech recognition scores (max. SRSs) in quiet was examined. In gap detection testing, narrow-band noises of the five center frequencies of 0.25, 0.5, 1.0, 2.0, 4.0 kHz were used as leading and trailing markers. Each of these two marker sounds was presented to the opposite ear at 20 dBSL with various gap durations between them.ResultsAbnormal GDTs were observed at one or more test frequencies in 17 of 23 patients. In 12 patients, abnormal GDTs were found at four or five test frequencies. These 12 patients included 4 patients with poor max. SRS less than 30%. However, no tendency was found for max. SRSs to be poorer as abnormal GDTs were observed for more test frequencies.ConclusionTemporal resolution measured by gap detection for dichotic stimuli was frequently reduced in patients with retrocochlear auditory dysfunction, and this reduction appeared to spread over a wide frequency range when speech recognition had markedly deteriorated. However, it also appeared that reduced temporal resolution for dichotic stimuli might not necessarily imply poor speech recognition in quiet.