Assessment of Amplification Benefit for a Subject with Cochlear Dead Regions

The purpose of the study was to determine the optimal hearing aid fitting procedure for a patient with well diagnosed high-frequency dead regions in both cochleas. The patient reported non-symmetrical hearing problems of sensorineural origin. The presence and frequency limits of dead regions was measured using the Threshold Equalizing Noise test (TEN). For binaural amplification four pairs of hearing aids were used. Three pairs of hearing instruments used were independent pairs with similar hearing aids in each pair. One pair of hearing aids was a pair of dependent devices with an ear-to-ear function. Two fitting methods were used: DSLi/o and NAL-NL1 and four different strategies of fitting were tested: the initial fitting based on the DSLi/o or NAL-NL1 method with necessary loudness corrections, the second fitting taking into account all available functions of hearing instruments, the third fitting (based on the second one) but with significantly reduced amplification well above one octave of frequency inside dead region and the final fitting with significantly reduced gain slightly below one octave inside dead regions. The results of hearing aids fitting were assessed using the Abbreviated Profile of Hearing Aid Benefit procedure (APHAB).