Abstract
Auditory brain stem responses (ABR) were studied in 30 patients with vertigo.
A click of 0.1 msec. duration was delivered monaurally with an interval of 100 msec. The electroencephalograms during 10 msec. after each stimulus were sampled for averaging. Electrodes were attached to the vertex (active) and to the mastoid (reference) ipsilateral to the stimulated ear and a ground electrode was placed on the mastoid of the opposite ear.
The response pattern of each wave, latency of wave I and times of I-III and I-V intervals were compared with those of normal hearing persons. Findings were considered to be abnormal when ABR showed the following response, i) latency of wave I was long-er than 1.6 msec. ii) I-III interval was longer than 2.2 msec. iii) I-V interval was longer than 4.2 msec. The results were as follows:
1) ABRs recorded from the 14 patients with vertigo due to labyrinthine lesions showed normal response pattern and prolongation of I-III interval was found in 4 cases.
2) In the patients with tumor at the CPA, wave I was recognized, but the following components were obscured in the ABR of the affected side.
3) ABRs from the patients with the infarction in the brain stem showed only wave I and the following waves showed so noisy pattern that each wave could not be identified.
4) ABRs in the patients with multiple sclerosis showed prolongation in latency and reduction in amplitude of the components originating from the site central to the lesion.
5) ABRs in the patients with lesions in the cerebellum or medulla showed no abnormalities.
6) Improvement of the clinical features was not always parallel to that of ABR.
