Alien hand syndrome in stroke: a report of 2 cases and review of the literature.

Alien hand syndrome (AHS) is a rare condition that occurs in patients with brain injury. It has also been described in stroke subjects, after callosotomy, and in corticobasal degeneration. The common feature of AHS is the involuntary autonomous activity of the affected extremity that is perceived as being controlled by an external force. AHS as a nosologic entity has been challenged. A complex variety of abnormal involuntary motor behaviors may follow cerebral lesions in different cerebral locations such as the corpus callosum, the parietal, or frontal regions. Although different subtypes of AHS have been distinguished, this classification clearly does not cover the wide clinical variety of abnormal (involuntary) motor behaviors of the upper extremity. In this report, we provide a review of literature on abnormal involuntary motor behaviors of the upper extremity after a stroke, which may help to improve early recognition of AHS and facilitate adjustment of rehabilitation therapy. Furthermore, we briefly discuss the complex variety of abnormal, involuntary motor behaviors that may follow after cerebral lesions, their anatomic substrates, the underlying mechanisms, and the prognosis.