Anatomical correlates of alien hand syndromes.

Objective: The objective of this study was to correlate various alien hand syndromes (AHS) with sites of lesion in 16 patients with anterior cerebral artery (ACA) territory infarction.

Background: All previous reports of AHS were case studies. Their clinico-anatomic correlations were still controversial. While the callosal lesion appears necessary for various types of AHS, which portion of the corpus callosum is associated with which syndrome is still not yet completely resolved.

Method: Sixteen patients with ACA territory infarction were selected from a stroke registry containing 7355 individuals. They were divided into three lesion groups according to location identified by computed tomography or magnetic resonance imaging: mesial frontal, callosal and combined mesial frontal and callosal. Neurobehavioral examination focused on the presence or absence of grasp reflex, various alien hand signs, intermanual conflict, and callosal disconnection syndrome. By gross visual analysis of the obtained data, a trend for clinicoanatomic correlation emerged.

Results: Patients with restricted mesial frontal lesions (three subjects), restricted anterior callosal lesions (four subjects) or "restricted" mesial frontal and anterior callosal lesions (two subjects) did not have symptoms of AHS. The remaining seven patients with extensive callosal injury involving the midbody and isthmus all had symptoms of AHS. Four of the patients with relatively isolated callosal involvement showed intermanual conflict (IMC) associated with a callosal AHS, while the remaining three patients with additional lesions involving the mesial frontal cortex showed impulsive reaching and grasping behaviors of the contralesional hand (a component of frontal AHS) and IMC (a component of callosal AHS).

Conclusions: A comparison of the lesions and symptoms of seven patients in two different groups shows that mesial frontal and anterior callosal (genu and rostral body) lesions are associated with a contralateral frontal AHS. Isolated involvement of the callosal midbody and isthmus is associated with a callosal AHS. When the mesial frontal cortex and corpus callosum (genu and whole body) are extensively involved, a mixed frontal and callosal AHS may occur in the same patient.