Visuomotor ataxia.

Visuomotor ataxia is a disorder of movement performed under visual control. It can occur in the absence of disturbance of ocular fixation and in the absence of spatial agnosia. This disorder may extend over the whole visual field or it may be localized to one visual half-field, right or left. It may involve both hands or one hand only, so that visuomotor ataxia may be divided into: (1) Unilateral visuomotor ataxia, localized to a single field. In this case it may affect both hands or a single hand. It is direct when the hand is ataxic in the ipsilateral visual field and it is crossed when the hand is ataxic in the contralateral visual field; (2) Bilateral visuomotor ataxia, involving the whole visual field. Each hand may be ataxic only in the contralateral visual field, that is, bilateral crossed visuomotor ataxia; or in the ipsilateral field when it is called bilateral direct visuomotor ataxia. The observed clinical variations which are described here imply the existence of both direct and crossed visuomotor connections, the latter probably crossing the corpus callosum in the splenium.