The effects of aminoglycoside-induced changes on the vestibular system were evaluated in three subjects who suffered significant damage over the course of treatment. Measurements of vestibulo-ocular reflex (VOR) function were made using sinusoidal and pseudorandom rotational stimuli between 0 to 5 days after initiation of drug therapy, during drug therapy, and up to 579 days following drug administration. All subjects tested at baseline evaluations had normal VOR function. During aminoglycoside therapy there was a precipitous drop in both the VOR time and gain constants. The decline in VOR function was larger at lower stimulus frequencies compared to high frequencies, resulting in a relative preservation of function in the high frequencies. Over a period of about a year, VOR high frequency gains recovered to within normal limits. However, the VOR time constants showed only a modest recovery and remained well below the normal range.
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