Neurological Disorders: Alien Hand Syndrome

Synonyms:
 Anarchic hand; Diagnostic dyspraxia;  Intermanual conflict; Magnetic apraxia; Unilateral apraxia; La main etrangere. 

Overview
     Alien hand syndrome  is a rare neurological disorder that causes hand movement without the person being aware of what is happening or having control over the action. The afflicted person may sometimes reach for objects and manipulate them without wanting to do so, even to the point of having to use the healthy hand to restrain the alien hand. A new study identified the areas of the brain involved in both voluntary and involuntary movement and found that neural activity was restricted to the primary motor cortex during the unconscious motor activity seen with AHS. The study will be published online in the official journal of the American Neurological Association.

      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 conceptualisation 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.


Clinical case:
     A 71-year-old right-handed woman developed acute left hemiparesis and visual hallucinations. She also complained that her left hand uncontrollably scratched her and pulled at her hair. Past medical history was notable for chronic hypertension and triple coronary artery bypass graft 6 years earlier. Two weeks before the illness, she had felt diffusely weak; another hospital had attributed this weakness to metoprolol toxicity. When her complaints did not subside after 2 days off medication, her husband brought her to the emergency room. Evaluation disclosed full orientation, left lower facial weakness, right gaze bias, left hemibody hypesthesia, and extensor posturing of the left limbs, with the left hand constantly clenched. Cranial CT scan indicated acute right parietal cortical infarct and extensive bilateral subcortical white matter ischemic changes.
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Sources:
http://jnnp.bmj.com/content/68/1/83.full
http://www.jsmf.org/meetings/2008/may/Mark%20VW%202008%20Alien%20hand%20syndrome.pdf
http://www.ncbi.nlm.nih.gov/pubmed/20220444
http://emedicine.medscape.com/article/1136037-overview