Recovery from vestibular ototoxicity

Objective: Determine whether subjects with documented vestibular ototoxicit y recover vestibular function and, if so, investigate the recovery dynamics . Study design: Prospective and retrospective reviews and repeated measures. Setting: Clinical research and technology center. Subjects: Twenty-eight subjects who received vestibulotoxic medications wer e followed for at least 12 months after initial treatment. Controls: Our subject sample was compared with a published database of norm al individuals. Interventions: All 28 subjects received systemically administered medicatio ns known to be ototoxic. The subjects' treating physicians controlled medic ation, dosage, and administration schedules. Main Outcome Measures: Tests of horizontal canal vestibuloocular function w ere performed, Subjects' auditory and vestibular symptoms were recorded. Results: Eleven subjects (39%) showed changes in horizontal canal vestibulo -ocular gain constant (GC) and/or time constant (TC) consistent with vestib ular ototoxicity. When tested I year after ototoxic drug administration, ei ght of the nine subjects who experienced ototoxic decrease in GC showed a r ecovery of GC to normal limits. Only one of the eight subjects who experien ced ototoxic decrease in TC showed recovery of TC to within normal limits. Ototoxicity onset and recovery were independent of baseline vestibular func tion, and ototoxicity onset did not correlate with cumulative dose of ototo xic medication. There was no relationship between subjective symptoms and o totoxicity onset. Conclusions: Recovery of GC after vestibular ototoxicity is more commonly o bserved than recovery of TC. Because ototoxic changes developed and continu ed in an unpredictable time and manner in relation to ototoxic drug adminis tration, we propose that once ototoxic changes in vestibulo-ocular reflex a re detected, ototoxic medications should be discontinued as soon as possibl e.