Sound lateralization and speech discrimination in patients with sensorineural hearing loss

Sound lateralization and speech discrimination abilities are both closely r elated to central auditory system function. In this study, we investigated the relationship between sound lateralization and speech discrimination in patients with sensorineural hearing loss (SNHL) of unknown aetiology or pre sbycusis. Interaural intensity difference (IID) and interaural time differe nce (ITD) discriminations were measured using a self-recording apparatus fo r dichotic sound presentation, and the means of bilateral maximum scores in speech discrimination tests were calculated. Subjects with normal sound la teralization had good speech discrimination scores above 70%, while those w ith abnormal sound lateralization had poor scopes below 70%. Some patients, however. had good speech discrimination but abnormal sound lateralization. These findings were obtained in both IID and ITD discrimination tests. Fur thermore, some subjects could not discriminate ITD, although all could disc riminate IID. These findings suggest that sound lateralization ability may be affected more than speech discrimination in SNHL of unknown aetiology or in presbycusis.