Medial frontal cortex infarction and the alien hand sign.

Two right-handed patients with infarction involving the left medial frontal cortex are described. Both patients exhibited a form of transcortical motor aphasia and a psychomotor disturbance involving the right arm characterized by forced grasping, motor perseveration, and the presence of apparently purposeful movements that appeared to be dissociated from conscious volition. The latter feature is noted to be identical to the alien hand sign as described in the left arm of commissurotomized patients and patients with callosal neoplasm or infarction. It is suggested that the observed dissociation of conscious intention from purposeful movement may be related to dysfunction of the medial frontal cortex contralateral to the impaired extremity as much as to hemispheric disconnection.