P2-71. Saccadic eye movements in Spinocerebellar Degeneration – study of saccades in eight directions

Abstract

Objectives The cerebellum is implicated in the control of saccadic eye movement but it is unknown how it differs for vertical and horizontal saccades, since vertical saccades have been rarely studied. To clarify the role of the cerebellum we studied saccades in hereditary spinocerebellar degeneration in two dimensional directions. Methods We compared saccade performance in 16 patients (SCA31 and SCA6) with that in 19 normal age-matched controls. We used the visual guided (VGS) and memory guided tasks (MGS) in which targets were presented in eight directions with 45 degrees separation, and recorded saccades with a video-based eye tracker. Results In SCA patients, latency of VGS was significantly delayed compared with normal subjects in vertical and oblique directions, which correlated with SARA scores. MGS latency was significantly delayed only in the oblique direction. Hypermetria was prominently detected in the vertical and oblique directions, but less in the horizontal directions. Conclusion Abnormal latency and dysmetria are easily detected for directions having vertical component. The cerebellum may be more involved in vertical than in horizontal saccade system, or vertical saccade system may be more susceptible to diseases than horizontal saccades. Further study of other diseases will be helpful to differentiate between these possibilities.