Title

The auditory steady state response in individuals with neurological insult of the central auditory nervous system

Date of Completion

January 2005

Keywords

Health Sciences, Audiology

Degree

Ph.D.

Abstract

The auditory steady state response (ASSR) has recently gained attention with respect to estimates of degree of hearing sensitivity and configuration of hearing loss, specifically in the pediatric population. However, to date, there have been no reports in the literature concerning the impact of neurological insult of the central auditory nervous system (CANS) on ASSR thresholds. This is of particular concern because many infants and children with neurological impairment are referred for electrophysiological hearing or auditory assessment. The purpose of the present investigation was to compare behavioral thresholds to ASSR estimated thresholds in subjects with confirmed CANS lesions. Neurological involvement was confirmed to be within the CANS through Magnetic Resonance Imaging. Comparisons were made between the experimental group and a normal control group matched for age and hearing sensitivity. All subjects underwent traditional audiometric assessment and ASSR measures. ASSR thresholds were obtained for the carrier frequencies of 500 and 2000 Hz with a 46 Hz modulation rate. Within and between group comparisons were made. The control group demonstrated strong correlation between their behavioral and estimated ASSR thresholds. This contrasted the neurological group which demonstrated poor correlations between same thresholds. Additionally, individuals with neurological impairment of the CANS exhibited elevated thresholds that were on average 24 dB greater at 2000 Hz than their behavioral thresholds. These results suggest that individuals with neurological insult may appear as hearing impaired or having greater hearing loss than is actually present. ^