Four alien hands for two hands after a callosal lesion.

Callosal lesions, associated or not to internal frontal lesions, may produc e different types of complex gestual behaviors. Four signs can be identifie d, each of which has been generally reported separately: the "alien hand" s ign, the "diagonistic apraxia", the "wayward hand" and the "callosal apraxi a". Some authors justify considering these signs as different entities, whi le others propose regrouping them either in an unique syndrome - the "alien hand" - or as two syndromes - the "frontal alien hand" and the "callosal a lien hand". We present the observation of a patient who presented with the four mentioned syndromes in association. In this context, we review the cli nical features of each of the four signs and the arguments supporting their individualization.