Detecting the recruitment phenomenon in adults using 80-Hz auditory steady-state response

Abstract

Objectives: The ASSR is used widely as an objective measurement of hearing in clinical settings because of its high frequency specificity. The recruitment phenomenon is generally detected using subjective evaluations which require direct communication with the patient. If the recruitment phenomenon can be detected with ASSR, it would facilitate diagnosis in patients with developmental disorders and infants.

Subjects and methods: We examined 2 groups of subjects: 10 subjects with unilateral hearing impairment in whom the recruitment phenomenon was detected by the alternate binaural loudness balance test and 12 normal subjects. We compared the relationships between the ASSR response and the stimulus sound pressure level in the 2 groups using the 80-Hz ASSR.

Results: The amplitude of ASSR was significantly higher in the impaired ear in hearing-impaired subjects compared to a normal ear in normal subjects. The latency of ASSR was significantly shorter in the impaired ear in hearing-impaired subjects than in the normal ear in the normal subjects.

Conclusion: This study showed that the recruitment phenomenon caused the higher amplitude and the shorter latency observed in hearing-impaired subjects in the 80-Hz auditory steady-state response (ASSR) in comparison with normal subjects.

Keywords: Auditory steady-state response; Inner ear hearing loss; Recruitment phenomenon.