[Difficulty in manual prehension under visual control (author's transl)].

Visuomotor ataxia causes difficulty in the prehension of objects under visual control which can occur without paralysis of ocular fixation and spatial agnosia. This can involve the total visual field or the right or left half-fields, and can affect both hands or one only. 1) Unilateral visuomotor ataxia is localized to the two right or left homonymous half-fields and can affect both hands or one only. It is direct when the ataxic hand is on the same side as the affected visual half-field, and crossed when the ataxic hand is contralateral to the affected visual half-field. 2) Bilateral visuomotor ataxia involves the total visual field. Each hand may be ataxic only for the contralateral visual field with a crossed bilateral visuomotor ataxia, or in the homolateral field with a direct bilateral visuomotor ataxia. The anatomical and clinical observations reported imply the existence of visuomotor connections, both direct and crossed, the latter crossing the median line through the corpus callosum.