SUPPRESSION OF THE OLIVOCOCHLEAR REFLEX: A NEUROTOXIC ADVERSE EFFECT OF VINCRISTINE

Abstract

OBJECTIVE: The purpose of this study was to examine the effects of a known neurotoxic regimen, such as the acute lymphocytic leukemia (ALL) Berlin-Frankfurt-Münster 95 (ALL-BFM-95) protocol, on the function of the medial olivocochlear bundle, which was assessed by recording suppression of the amplitudes of distortion-product otoacoustic emissions (DPOAEs) when white noise was applied simultaneously to the contralateral ear. METHODS: Our population consisted of 3 groups of children with ALL. A baseline examination was performed before the beginning of therapy. DPOAE-suppression measurements were repeated after 4 weekly doses of vincristine in the first group (n = 12), after 8 weekly doses in the second group (n = 12), and 3 years after completion of the protocol in the third group (n = 23). In the third group, a subgroup of 12 children who were exposed to low-dose gentamicin (<13 days) and another 11 children who were exposed to high gentamicin doses (>23 days) were evaluated. RESULTS: At baseline examination, all groups presented significant suppression at all frequencies. Efferent mediated DPOAE suppression was still present after 4 sessions of vincristine. However, after 8 vincristine sessions, instead of suppression, an increase of amplitudes was noted at 5 (of 12) frequencies. In the subgroups examined 3 years after ALL-BFM-95, the olivocochlear reflex had recovered. CONCLUSIONS: Enhancement or no significant suppression of OAEs by contralateral noise indicates a probable vincristine-induced insult to the efferent cochlear innervation. This adverse effect seems to take place early in the course of chemotherapy and is slowly reversed a few years after chemotherapy. The clinical implications of these findings may need additional investigation.