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The alien hand sign. Localization, lateralization and recovery
1Department of Physiology Temple University School of Medicine Pennsylvania.
American Journal of Physical Medicine & Rehabilitation
|October 1, 1990
Summary
Alien hand sign involves involuntary limb movements due to frontal lobe damage. This study links alien hand sign to specific medial frontal cortex lesions and proposes a dual premotor systems hypothesis for motor recovery after stroke.
Area of Science:
- Neuroscience
- Neurology
- Cognitive Science
Background:
- The alien hand sign is characterized by a patient's feeling of estrangement from their own hand, which exhibits involuntary, seemingly purposive movements.
- This phenomenon is often associated with frontal lobe damage and can include grasp reflexes and magnetic apraxia.
Observation:
- Four new cases of alien hand sign are presented, affecting either the right or left hand in right-handed subjects.
- Clinical findings consistently linked these alien hand behaviors to extensive unilateral damage in the medial frontal cortex contralateral to the affected hand.
Findings:
- Alien hand movements gradually resolve over 6-12 months post-stroke.
- The study supports the dual premotor systems hypothesis, suggesting alien hand behavior arises from unconstrained lateral premotor system activity in the damaged hemisphere.
Implications:
- Understanding alien hand sign mechanisms offers insights into motor control and recovery after brain injury.
- The findings highlight the role of medial and lateral premotor systems in volitional movement and the potential for compensatory mechanisms in stroke recovery.