From the Guidelines
Alien hand syndrome is primarily caused by damage to specific brain regions, particularly the corpus callosum, supplementary motor area, or anterior cingulate cortex, often resulting from neurodegenerative diseases, stroke, brain tumors, or surgical procedures. The condition is characterized by involuntary, purposeful movements of one hand without conscious control or awareness, as if the hand has a "mind of its own" 1. This damage disrupts normal communication between brain regions responsible for intention and motor control, leading to the affected hand performing complex movements, such as grabbing objects, unbuttoning clothing, or fighting with the other hand. Key factors contributing to alien hand syndrome include:
- Neurodegenerative diseases like corticobasal degeneration (CBD), which is a tauopathy characterized by abnormal accumulation of tau proteins in the brain, leading to asymmetric limb clumsiness, limb rigidity, and dystonia, including the "alien limb phenomenon" 1
- Stroke or brain tumors that affect the corpus callosum or other motor control areas
- Surgical procedures, such as corpus callosotomy, that separate the brain hemispheres Treatment focuses on managing the underlying condition and using behavioral strategies to reduce unwanted movements, with no specific medication regimen for alien hand syndrome itself, although treating the underlying cause may help alleviate symptoms 1.
From the Research
Causes of Alien Hand Syndrome
The causes of alien hand syndrome (AHS) are varied and can be attributed to several factors, including:
- Damage to the corpus callosum, as reported in studies 2, 3
- Infarction or neurodegenerative disease affecting the brain, particularly in areas such as the parietal lobe, frontal lobe, or cingulate gyrus 4, 2, 5
- Stroke, which can cause damage to specific brain regions, leading to AHS 4, 6
- Tumors or other vascular disorders that affect critical brain regions 5
- Lesions in the parietal/occipital lobes, which can result in posterior alien hand syndrome 6
Brain Regions Affected
The brain regions affected in AHS can be categorized into different types, including:
- Frontal type: associated with damage to the frontal lobe 5
- Callosal type: associated with damage to the corpus callosum 2, 5, 3
- Posterior type: associated with damage to the parietal/occipital lobes 6
- Parietal type: associated with damage to the parietal lobe 4, 5
Underlying Pathology
AHS can be an initial presentation of serious underlying pathology, such as stroke, neurodegenerative disease, or corpus callosum damage 4, 2, 5. The syndrome can also be associated with a range of peculiar sensations, including feelings of limb estrangement, alien control, and involuntary mirroring or restraining of movements 5, 3.