An Evaluation of Electrodiagnostic Measures of Hearing

Abstract

The effectiveness of three non-invasive electrophysiological techniques in the assessment of the subjective hearing thresholds was evaluated in normal and hearing impaired populations. 1. The Vertex Potential was used to establish objective auditory thresholds in normal adults and in adults and children with known hearing defects. Comparison of subjective and objective hearing thresholds revealed the vertex potential to be most reliable as a measure of auditory acuity in the group of normal adults; the groups of adult and child hearing defects showed both greater discrepancies and variability between subjective and objective assessment. 2. The Post-Auricular Myogenic Potential was investigated in two groups of normal adults. It was found to provide a less reliable assessment of auditory acuity than either the vertex potential or the brainstem potentials mainly on account of its variability and dependancy on resting muscle tone. 3. Brainstem Evoked Potentials were recorded in a large group of normal adults. The N4 component (Jewett's V wave) was found to provide a close and reliable estimation On subjective hearing level. The observed Stability in the characteristics of the brainstem potentials would support their use in neurological assessment, but initial findings indicate a need for the development of more comprehensive age and sex related normal data. Further investigations of the vertex potential using linguistic and non-linguistic stimuli failed to produce any clear evidence of the reflection of stimulus meaning in the characteristics of the vertex potential. The results, instead, would support the on-response nature of the vertex potential whose characteristics are primarily determined by the physical properties of the stimulus.