Alien Hand, Alien Limb

Alien Hand, Alien Limb

An alien limb, most usually the arm but occasionally the leg, is one that manifests slow, involuntary, wandering (levitating), quasipurposive movements. An arm so affected may show apraxic difficulties in performing even the simplest tasks and may be described by the patient as uncooperative or "having a mind of its own" (hence alternative names such as anarchic hand sign and le main étranger). These phenomena are often associated with a prominent grasp reflex, forced groping, intermanual conflict, and magnetic movements (q.v.) of the hand.

Different types of alien hand have been described, reflecting the differing anatomical locations of underlying lesions:

• Anterior or motor types:
  • Callosal: characterized primarily by intermanual conflict;
    Frontal: shows features of environmental dependency, such as forced grasping and groping and utilization behavior.
• Sensory or posterior variant:
  • Resulting from a combination of cerebellar, optic, and sensory ataxia; rare.
  A paroxysmal alien hand has been described, probably related to seizures of frontomedial origin.
  Recognized pathological associations of alien limb include:

Corticobasal (ganglionic) degeneration
Corpus callosum tumors, hemorrhage
Medial frontal cortex infarction (territory of the anterior cerebral artery)
Trauma and hemorrhage affecting both corpus callosum and medial frontal area
Alzheimer’s disease (very rare)
Posterior cerebral artery occlusion (sensory variant)
Following commissurotomy (corpus callosotomy alone insufficient).

Functional imaging studies in corticobasal degeneration, along with the evidence from focal vascular lesions, suggest that damage to and/or hypometabolism of the medial frontal cortex (Brodmann area 32) and the supplementary motor area (Brodmann area 6) are associated with alien limb phenomena. More generally, it seems that these areas are involved in the execution of learned motor programs, and damage thereto may lead to the release of learned motor programs from voluntary control.

 

References
Ay H, Buonanno FS, Price BH, Le DA, Koroshetz WJ. Sensory alien hand syndrome: case report and review of the literature. Journal ofNeurology, Neurosurgery and Psychiatry 1998; 65: 366-369
Doody RS, Jankovic J. The alien hand and related signs. Journal ofNeurology, Neurosurgery and Psychiatry 1992; 55: 806-810
Feinberg TE, Schindler RJ, Flanagan NG, Haber LD. Two alien hand syndromes. Neurology 1992; 42: 19-24
Josephs KA, Rossor MN. The alien limb. Practical Neurology 2004; 4: 44-45
Sawle GV, Brooks DJ, Marsden CD, Frackowiak RSJ. Corticobasal degeneration: a unique pattern of regional cortical oxygen hypometabolism and striatal fluorodopa uptake demonstrated by positron emission tomography. Brain 1991; 114: 541-556

 

Cross References

Alien grasp reflex; Apraxia; Ataxia; "Compulsive grasping hand"; Forced groping; Grasp reflex; Intermanual conflict; Levitation; Magnetic movements; Utilization behavior