Read more about this disease, some with Classification – Types – Signs and symptoms – Genetics – Pathophysiology – Diagnosis – Screening – Prevention – Treatment and management – Cures and much more, some including pictures and video when available.
Alien hand syndrome (anarchic hand or Dr. Strangelove syndrome) is an unusual neurological disorder in which one of the sufferer’s hands seems to take on a mind of its own. AHS 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 other brain surgery, strokes, or infections.
An alien hand sufferer can feel normal sensation in the hand, but believes that the hand, while still being a part of their body, behaves in a manner that is totally distinct from the sufferer’s normal behavior. They lose the ‘sense of agency’ associated with the purposeful movement of the limb while retaining a sense of ‘ownership’ of the limb. They feel that they have no control over the movements of the ‘alien’ hand, but that, instead, the hand has the capability of acting autonomously–i.e. independent of their voluntary control. The hand effectively has ‘a will of its own.’ Alien hands can perform complex acts such as undoing buttons, removing clothing, and manipulating tools. Alien behavior can be distinguished from reflexive behavior in that the former is flexibly purposive while the latter is obligatory. Sometimes the sufferer will not be aware of what the alien hand is doing until it is brought to his or her attention, or until the hand does something that draws their attention to its behavior
A related syndrome described by the French neurologist François Lhermitte involves the release through disinhibition of a tendency to compulsively utilize objects that present themselves in the surrounding environment around the patient. The behavior of the patient is, in a sense, obligatorily linked to the “affordances” (using terminology introduced by the American ecological psychologist, J.J. Gibson) presented by objects that are located within the immediate peri-personal environment. 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 their behavior in a general social context, a condition also identified by Lhermitte, and referred to as “Environmental Dependency Syndrome”.
Sufferers of alien hand will often personify the rogue limb, for example believing it to be “possessed” by some intelligent or alien spirit or an entity that they may name or identify. There is a clear distinction between the behaviors of the two hands in which the affected hand is viewed as “wayward” and sometimes “disobedient” and generally out of the realm of their own voluntary control, while the unaffected hand is under normal volitional control. At times, particularly in patients who have sustained damage to the corpus callosum that connects the two cerebral hemispheres (see also split-brain), the hands appear to be acting in opposition to each other. For example, one patient was observed putting a cigarette into her mouth with her intact, ‘controlled’ hand (her right, dominant hand), following which her alien, non-dominant, left hand came up to grasp the cigarette, pull the cigarette out of her mouth, and toss it away before it could be lit by the controlled, dominant, right hand. The patient then surmised that “I guess ‘he’ doesn’t want me to smoke that cigarette”. This type of problem has been termed “intermanual conflict” or “diagonistic apraxia”.
This condition has been thought to provide a fascinating window into the nature of human consciousness as it relates to voluntary action, processes underlying decision making and conscious volition, as well as the general nature of human agency and intentionality. Besides its relevancy to the understanding of the neurobiologic basis of human action, these observations would appear to have significant relevance for the general philosophy of action. In that the recognition of this condition depends upon linking an observation of a particular behavior–the appearance of a purposeful limb behavior–to either a direct report or inference regarding the experience of the actor in the course of producing the movement, and then correlating this relation to brain pathophysiology, alien hand syndrome and its study may be viewed as within the purview of neurophenomenology.
There are several distinct subtypes of Alien Hand that appear to be associated with specific types of triggering brain injury. Damage to the corpus callosum can give rise to “purposeful” actions in the sufferer’s non-dominant hand (a right-handed sufferer’s left hand will turn alien, and the right hand will turn alien in the left-handed) as well as a problem termed “intermanual conflict” in which the two hands appear to be directed at opposing purposes, whereas unilateral injury to the brain’s frontal lobe can trigger reaching, grasping and other purposeful movements in the contralateral hand. With frontal lobe injury, 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 the “frontal” 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.
A distinct “posterior” form of alien hand syndrome is associated with damage to the parietal lobe and/or occipital 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. Alien movements in the posterior form of the syndrome also tend to be less coordinated and show a coarse ataxic motion that is generally not observed in the frontal form of the condition. The alien limb in the posterior form of the syndrome may be seen to ‘levitate’ upward and away from contact surfaces. Alien hand movement in the posterior form may show a typical posture, sometimes referred to as a ‘parietal hand’ or ‘instinctive avoidance reaction’ (a term introduced by neurologist Derek Denny-Brown), in which the digits move into a fully 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 (e.g., chorea, or myoclonus). In both the frontal and the posterior forms of the alien hand syndrome, the patient’s reactions to the limb’s apparent capability to perform goal-directed actions independent of conscious volition is similar.
Patients thus will often indicate that the apparently purposeful movements of the alien hand are “wayward” or “disobedient”, in that they are not being generated through the exertion of their own voluntary will or directed toward goals that have been consciously produced, but, instead, the alien hand appears to behave independent of conscious will, effectively “on its own”. The alien hand may even engage in socially inappropriate behavior in a public venue causing significant embarrassment and distress. Patients may react with dismay and concern at the ability of the hand to perform purposeful actions that are independent of their own sense of control over the movement, a phenomenon termed “auto-criticism”.
[tubepress mode=’tag’, tagValue=’Alien hand syndrome’]