[Four "alien" hands for two hands after a lesion in corpus callosum].

Callosal lesions, associated or not to internal frontal lesions, may produce different types of complex gestural behaviors. Four signs can be identified, each of which has been generally reported separately: the "alien hand" sign, the "diagnostic apraxia", the "wayward hand" and the "callosal apraxia". Some authors justify considering these signs as different entities, while others propose regrouping them either in an unique syndrome--the "alien hand"--or as two syndromes--the "frontal alien hand" and the "callosal alien hand". We present the observation of a patient who presented with the four mentioned syndromes in association. In this context, we review the clinical features of each of the four signs and the arguments supporting their individualization.