Right-sided anarchic (alien) hand: a longitudinal study.

A patient with a bilateral frontal vascular lesion, encroaching upon the mesial cortex on the left and damage of the corpus callosum showed the 'alien hand' phenomenon on the right. The various hypotheses as to the nature of the lesion for the alien hand phenomenon to appear are discussed. It is proposed that an acute clinical condition, following a lesion of the corpus callosum only, should be differentiated from a chronic condition resulting from the additional fronto-mesial lesion.