SACCADES IN GILLES-DE-LA-TOURETTES-SYNDROME

Gilles de la Tourette's syndrome (GTS) is presumed to be an inherited disorder with an unclear pathophysiology. An involvement of the basal ganglia is suspected. Besides vocal ties, one of the main symptoms is the presence of motor ties. As eye movements are a specialized part of the motor system, we investigated whether they differed in some typic al way in GTS patients. To study the control of saccades in GTS, diffe rent paradigms were used to elicit saccades, which were either externa lly triggered and visually guided or internally triggered and without visual target. GTS patients (n = 10) showed a significant increase of the latency of antisaccades, a highly impaired performance of sequence s of memory-guided saccades, and an isolated reduction of the peak vel ocity in the antisaccades. Overall the results were similar to those f ound with similar paradigms in patients with Huntington's disease (HD) . In analogy to the known pathology of HD, these findings can be attri buted to ascending loops from the basal ganglia that inappropriately a ctivate the frontal cortex, especially some of the eye movement-relate d areas there. This impairment seems to be a rather specific effect, s ince some oculomotor features that are preserved by structures of the frontal cortex, such as the effect of a fixation target on saccadic la tency (''gap effect''), were normal.