Vestibular Responsiveness in Normal- And in Impaired-Hearing Children.

Abstract

Vestibular responsiveness of 90 normal- and of 31 impaired-hearing children from 4 through 16 years of age was investigated using a modified Barany-chair test to provide horizontal angular acceleratory stimuli to the semi-circular canals and a parallel swing to provide alternating horizontal linear acceleratory stimuli to the otolithic end organs. Children's eye movements behind a sleep mask in response to vestibulo-ocular reflexes initiated by the angular and linear accelerations were recorded via electronystagmography and telemetry. Mean frequency, amplitude, and slow phase velocity of primary postrotatory nystagmus and presence or absence and latency of secondary per- and postrotatory nystagmus were obtained for each child. Compensatory eye movements in response to alternating linear accelerations produced by swinging were recorded. When possible, children reported their aftersensations of movement and visceral reactions to both tests. All children had some per- and postrotatory primary nystagmus in response to cessation of rotation; most children had per- and postrotatory secondary nystagmus as well. Differences in quality and quantity of both primary and secondary nystagmus existed among children. Compensatory eye movements occurred for a minimum of four oscillations of the swing in all children who maintained a sufficient level of mental alertness while swinging. During rotatory testing 10 hearing-impaired children had consistently diminished nystagmic responses and denied any aftersensations or visceral reactions, all suggestive of bilateral semi-circular canal pathology, but had criterion-level compensatory eye movements suggestive of normal otolithic function. The remaining 21 hearing-impaired children tested had eye movements and reports of aftersensation and visceral reaction in response to both tests comparable to those of control children their age. Results of this study suggest that one can evaluate both semi-circular canal and otolithic responsiveness in normal- and impaired-hearing children as young as 4 years of age with minimal anxiety and discomfort to the subject using a modified Barany procedure and a parallel swing with electronystagmography and telemetry. Two methods of classifying nystagmus in response to rotatory testing as normal or below normal are offered. Early screening for peripheral vestibular deficits in hearing-impaired children is advisable.