AHS was first identified in 1909 and there have only been

40 to 50 recorded cases since. It's believed that other

instances may have been misdiagnosed as part of an existing

mental health disorder. The rarity and non-threatening nature

of AHS has led to infrequent research and a lack of hard data,

resulting in a condition that's largely mysterious. Very recently,

however, new clues have been uncovered that help pinpoint

the part of the brain that is active during AHS episodes

•Damage to the corpus callosum can give rise to "purposeful" actions in the sufferer's non-dominant hand (an individual who is left-hemisphere-dominant will experience the left hand becoming alien, and the right hand will turn alien in the person with right-hemisphere dominance) as well as a problem termed "intermanual conflict" in which the two hands appear to be directed at opposing purposes.

•The patient typically shows little evidence of limb paresis.

•Unilateral injury to the brain's frontal lobe can trigger reaching, grasping and other purposeful movements in the contralateral hand.

•With anteromedial frontal lobe injuries, these movements are often exploratory reaching movements in which external objects are frequently grasped and utilized functionally, without the simultaneous perception on the part of the patient that they are "in control" of these movements.

•Once an object is maintained in the grasp of this "frontal variant" form of alien hand, the patient often has difficulty with voluntarily releasing the object from grasp and can sometimes be seen to be peeling the fingers of the hand back off the grasped object using the opposite controlled hand to enable the release of the grasped object.

•This condition, termed “utilization behavior”, is most often associated with extensive bilateral frontal lobe damage and might actually be thought of as "bilateral" alien hand syndrome in which the patient is compulsively directed by external environmental contingencies (e.g., the presence of a hairbrush on the table in front of them elicits the act of brushing the hair) and has no capacity to "hold back" and inhibit pre-potent motor programs that are obligatorily linked to the presence of specific external objects in the peri-personal space of the patient.

•When the frontal lobe damage is bilateral and generally more extensive, the patient completely loses the ability to act in a self-directed manner and becomes totally dependent upon the surrounding environmental indicators to guide his behavior in a general social context, a condition also identified by Lhermitte (1986), and referred to as ”Environmental Dependency Syndrome”.

• A distinct "posterior variant" form of alien hand syndrome is associated with damage to the posterolateral parietal lobe and/or occ`ipital lobe of the brain. • The movements in this situation tend to be more likely to withdraw the palmar surface of the hand away from environmental contact rather than reaching out to grasp onto objects to produce palmar tactile stimulation, as is most often seen in the frontal form of the condition. • The alien limb in the posterior variant of the syndrome may be seen to 'levitate' upward into the air and away from contact surfaces. • Alien hand movement in the posterior variant may show a typical posture, sometimes referred to as a 'parietal hand' or 'instinctive avoidance reaction' in which the digits move into a highly extended position and the palmar surface is pulled back away from approaching objects. • The 'alien' movements, however, remain purposeful and goal-directed, a point which clearly differentiates these movements from other forms of involuntary limb movement.

TREATMENT

Although there is no known formal (primary) treatment for alien hand syndrome at this time, the symptoms can be reduced and managed to some degree by keeping the alien hand occupied and involved in a task.

Patients with the "frontal" form of alien hand, who would reach out to grasp onto different objects as they were walking, were given a cane to hold in the alien hand while walking. With the cane firmly in the grasp of the alien hand, it would generally not release the grasp and drop the cane in order to reach out to grasp onto a different object.

In the presence of unilateral damage to a single cerebral hemisphere, there is generally a gradual reduction in the frequency of alien behaviors observed over time and a gradual restoration of voluntary control over the affected hand. Exactly how this may occur is not well understood, but a process of gradual recovery from alien hand syndrome when the damage involves a single hemisphere has been reported.

TREATMENT

Patient is trained to perform a specific task, such as moving the alien hand to contact a specific object or a highly salient environmental target, which is a movement that the patient can learn to generate voluntarily through focused training in order to effectively override the alien behavior.

Another method involves simultaneously "muffling" the action of the alien hand and limiting the sensory feedback coming back to the hand from environmental contact by placing it in a restrictive "cloak" such as a specialized soft foam hand orthosis or, alternatively, an everyday oven mitt.

Prepared by,Hafsa MohammedNruthyathiFemi Thankam JohnsSoumya KVMalavika MIsrath Elona