Alien Hand Syndrome
Alien hand syndrome is an interesting phenomenon that is rarely observed in clinical practice. This clinical condition is characterized by the failure of one limb to comply with the will of the human mind.
The two opposite sides of the body are usually at conflict with each other where one side fails to carry out the desired function and performs involuntary movements as if it had “its own will”.
These unintended movements could involve the hand abruptly choking the person’s own throat or even grasping various other items in his/her vicinity. In addition, there is a marked sensation of alienation in the affected limb and most of the patients seldom consider it as a part of their own body.
The alien hand syndrome
“A 77-year-old woman presented with the complaint of observing her left hand moving without her knowledge while watching television. Her left hand stroked her face and hair as if somebody was controlling it. These movements lasted only half an hour but on recovery, she had left hemiparesis. Alien hand syndrome as the presentation of cardioembolic stroke is extremely rare but can be terrifying to patients.”
The pathophysiology of alien hand syndrome is explained by cerebral lesions involving the corpus callosum which is the connecting bridge between the two cerebral hemispheres. Moreover, any lesion altering the neuroanatomy of medial frontal lobe and parietal cortex may also underlie the development of this anomaly.
It has been proposed that any damage inflicted upon these cerebral regions may result in their release from the motor neuronal circuit, thereby leading to uncontrolled contralateral limb movements. Moreover, parietal lobe lesions can also promote a feeling of contralateral hemi-neglect. A total of four different categories of the syndrome are recognized, as under:
- Intermanual conflict. It occurs when actions of both hands oppose each other.
- Alien hand sign. In this form, a person feels as if a limb or a hand does not belong to them.
- Anarchic hand. It takes place when the involved limb performs purposeful actions against one’s own will.
- Supernumerary hand. The person feels as if they have an extra hand or an extra limb.
- Some cases even develop autocriticism where a person would slap the alien limb with their normal hand. Moreover, some cases even try to personify their alien hand by giving them random names.
Only a handful of medications are used in the therapeutic management of alien hand syndrome. These include anti-depressants and botulinum toxin.
However, no medication has been particularly approved or recommended for this purpose. Most of the practitioners emphasize upon rehabilitation and behavioural modulation therapy.
Abnormal hand movements can be restricted by means of engaging it in different activities such as holding a cane, or sometimes even by giving the alien hand direct command of action. Mirror box therapy is another technique which has been found effective for the alien hand syndrome secondary to corpus callosal stroke.
Evidence remains to be miniscule regarding the exact aetiology of alien hand syndrome since there are relatively limited cases of the disease while some can even remain undiagnosed. With a scanty literature, it is essential to expand the scope of research into this rare clinical entity.