Alien hand syndrome, (AHS) is a rare neurological disorder that causes hand movement without the person being aware of what is happening or having control over the action. The afflicted person may sometimes reach for objects and manipulate them without wanting to do so, even to the point of having to use the healthy hand to restrain the alien hand.^[1]

Alien hand syndrome is best documented in cases where a person has had the two hemispheres of their brain surgically separated, a procedure sometimes used to relieve the symptoms of extreme cases of epilepsy. It also occurs in some cases after brain surgery, stroke, infection, tumor, aneurysm and specific degenerative brain conditions such as Alzheimer’s disease and Creutzfeldt–Jakob disease.^[2] Other areas of the brain that are associated with alien hand syndrome are the frontal, occipital and parietal lobes.^[3][4]

The first known case described in the medical literature appeared in a detailed case report published in German in 1908 by the preeminent German neuro-psychiatrist, Kurt Goldstein.^[5] In this paper, Goldstein described a right-handed woman who had suffered a stroke affecting her left side from which she had partially recovered by the time she was seen. However, her left arm seemed as though it belonged to another person and performed actions that appeared to occur independent of her will.

The patient complained of a feeling of “strangeness” in relationship to the goal-directed movements of the left hand and insisted that “someone else” was moving the left hand, and that she was not moving it herself. Goldstein reported that, as a result of this report, “she was regarded at first as a paranoiac.” When the left hand grasped an object, she could not voluntarily release it. The somatic sensibility of the left side was reported to be impaired, especially with aspects of sensation having to do with the orienting of the limb. Some spontaneous movements were noted to occur involving the left hand, such as wiping the face or rubbing the eyes; but these were relatively infrequent. Only with significant effort was she able to perform simple movements with the left arm in response to spoken command, but these movements were performed slowly and often incompletely even if these same movements had been involuntarily performed with relative ease before while in the abnormal ‘alien’ control mode.

Based on these remarkable observations, Goldstein developed a “doctrine of motor apraxia” in which he discussed the process involved in the generation of voluntary action and interpreted these findings in the context of a proposed central structure organized around the perception and internal representation of the space-time continuum encompassing memory, will, and other higher cognitive processes. Goldstein maintained that a unified conceptual organization and general gestalt of space-time in which all aspects of relevant sensory perception of both the physical body (i.e. via interoception) and external space (i.e. via exteroception) were integrated was necessary both for object perception as well as for successful goal-directed dynamic bodily action in relationship to extrapersonal space and the objects located therein. In his classic papers reviewing the wide variety of disconnection syndromes associated with focal brain pathology, Norman Geschwind commented that Kurt Goldstein “was perhaps the first to stress the non-unity of the personality in patients with callosal section, and its possible psychiatric effects.”^[6]

Anarchic hand syndrome and alien hand syndrome are two similar but separate disorders. In both there are unintended but purposeful and autonomous movements of the upper limb and intermanual conflict. Anarchic hand is usually diagnosed as opposed to alien hand syndrome because it tends to be more associated with motor impairments as the patients acknowledge the hand as theirs but are frustrated by its unintended actions.^[7] In alien hand syndrome the individual tends to display more sensory deficits as they dissociate themselves from the hand and its actions, frequently remarking on the hand’s behaviour as if it does not belong to them.^[8]

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