Catch up saccades in vestibular hypofunction: a contribution of the cerebellum?

Abstract

Introduction: Long-term deficits of the vestibulo-ocular reflex (VOR) elicited by head rotation can be partially compensated by Catch-up Saccades (CuS). These saccades are initially visually guided but their latency can greatly decrease resulting in Short Latency CuS. It is still unclear what triggers these CuS and what are the underlying neural circuits. In this study, we aimed at evaluating the impact of cerebellar pathology on CuS by comparing their latency between two groups of patients with bilateral vestibular hypofunction, with or without additional cerebellar dysfunction. Method: We recruited 12 patients with both bilateral vestibular hypofunction and cerebellar dysfunction (BVH-CD group) and 12 patients with isolated bilateral vestibular hypofunction (BVH group). Both groups were matched for age and residual VOR gain. Subjects underwent video head impulse test recording of the horizontal semi-circular canals responses as well as recording of visually guided saccades in the Step, Gap and Overlap paradigms. Latency and gain of the different saccades were calculated. Results: Mean age for BVH-CD and BVH was respectively 67.8 and 67.2 years and mean residual VOR gain was respectively 0.24 and 0.26. Mean latency of the first catch-up saccade was significantly longer for the BVH-CD group than for the BVH group (204ms vs 145ms, p<0.05). There was no significant difference in the latency of visually guided saccades between the two groups, for none of the three paradigms. Conclusion: Our results suggest that the cerebellum plays a role in the generation of compensatory SL-CuS observed in BVH patients.