[Slow eye movements (slow saccades) in Wilson's disease].

Slow eye movements or slow saccades are relatively rare conditions in Wilson's disease where selective impairments of saccades are observed. The authors have a case of Wilson's disease showing a defect of saccades in all directions, with the complete preservation of smooth pursuit eye movements. T2-weighted images revealed abnormalities of signal intensity in bilateral pontine tegmentum, besides putaminal and thalamic lesions commonly seen in the previous reports. A rather selective disturbance of saccade eye movements due to the pontine tegmentum is consistent with the concept, as yet mainly based on experimental work on animals, of an anatomical segregation of the brainstem pathways for smooth pursuit eye movements, saccades, and vestibular and optokinetic patterns. Whereas the basal brainstem, especially basal pons, subserves smooth pursuit eye movements, saccades and reflex-like eye movements are mediated by the pontine tegmentum. The authors' case offers a support that dissociating eye movement disorders are due to the restricted lesions mentioned above.