Horizontal and vertical saccadic eye movement abnormalities in Huntington's chorea.

With a newly developed infrared reflection technique, voluntary saccadic eye movements (VOLS), visually evoked saccades (VES) and unsuppressed visually evoked reflex saccades (USVERS) were measured in 11 patients with Huntington's chorea. Abnormalities, including latency increase, peak velocity decrease and undershoot dysmetria with multiple step saccades were found in all types of saccadic eye movements. Peak velocity decrease and undershoot dysmetria can be explained by dysfunction of the brainstem reticular formation in Huntington's chorea. USVERS and square wave jerks occurred abnormally frequently and showed direction-dependent differences. Both were more frequent in horizontal than in vertical direction. Frequency of USVERS and square-wave jerks tended to be correlated. These findings point to disinhibited superior colliculi as a possible common supranuclear origin of USVERS and square-wave jerks in Huntington's chorea.