Alien hand syndrome is a rare neurological disorder where a patient's hand will move in a seemingly purposeful manner without the patient being consciously aware of it. In extreme cases, the patient may have little or no voluntary control over the hand, having to use the other hand to restrain it. In addition, the alien hand also has lessened sensation to touch or pain. It is most often associated with patients who have undergone a hemispherectomy.
The condition was first documented in 1908 in a woman who had a stroke and thereafter lost control over her left hand. In fiction, the most common depiction is in Stanley Kubrick's "Dr. Strangelove" where the title character, played by Peter Sellers, has a left hand that acts as if it were part of a Nazi officer.
Although the causes of the condition are well known, the etiology of the condition is poorly understood. The best current explanation is that the syndrome occurs when the premotor cortex is separated from the primary motor cortex causing the two to act independently instead of in concert as they do in a normal brain.
There is no real treatment for the condition, and it is often recommended that the alien hand be given a task, such as holding something, to keep it occupied.