Subjective experience, involuntary movement, and posterior alien hand syndrome.

The alien hand syndrome, as originally defined, was used to describe cases involving anterior corpus callosal lesions producing involuntary movement and a concomitant inability to distinguish the affected hand from an examiner's hand when these were placed in the patient's unaffected hand. In recent years, acceptable usage of the term has broadened considerably, and has been defined as involuntary movement occurring in the context of feelings of estrangement from or personification of the affected limb or its movements. Three varieties of alien hand syndrome have been reported, involving lesions of the corpus callosum alone, the corpus callosum plus dominant medial frontal cortex, and posterior cortical/subcortical areas. A patient with posterior alien hand syndrome of vascular aetiology is reported and the findings are discussed in the light of a conceptualization of posterior alien hand syndrome as a disorder which may be less associated with specific focal neuropathology than are its callosal and callosal-frontal counterparts.