This article includes discussion of alien hand syndrome, alien limb phenomenon, anarchic hand, diagonistic dyspraxia, groping-grasping reaction, intermanual conflict, magnetic apraxia, Strangelovian hand, unilateral apraxia, and wayward hand. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Alien hand syndrome describes any of several neurologic disorders that share the appearance of seemingly purposeful movement by 1 hand (or less often, 1 leg) that is dissociated from the conscious intent of the patient, giving the impression that the limb is acting on its own. The author reviews the different manifestations and causes of this complex disorder, as well as variants of this phenomenon. The disorder has been recognized in diverse cerebral illnesses, including stroke, corticobasal syndrome, and multiple sclerosis, as well as following corpus callosotomy for refractory epilepsy. Although primarily an adult disorder, alien hand may also occur in children. Several mechanisms probably account for alien hand, including the reflexive elicitation of compulsive grasping of objects that are touched or viewed and the performance of self-oppositional activities by 1 cerebral hemisphere that has been largely disconnected from the other hemisphere’s verbalized intentions, thus preventing insight into the source of the movements (such as closing a drawer after it had been opened by the other hand). However, it remains unclear why 1 hemisphere opposes the activity of the other. The disorder is uncommon and generally recovers when it follows acute brain illness such as stroke, but it nonetheless can cause considerable embarrassment and, rarely, even self-injury. When alien hand occurs with neurodegenerative diseases, such as corticobasal syndrome or multiple sclerosis, the prognosis for recovery is poor. Therapies for this disorder have not been well developed. Several pharmacologic approaches have been published, but without replication. Verbal commands from another individual or generated by the patient himself or herself can control the phenomenon, but it is not clear whether this approach can confer lasting benefit. Some evidence indicates that compulsive grasping may be modulated by the degree of danger involved, reflecting some amount of “top-down” control. A novel approach has shown that mirror box therapy may curtail uncooperative behavior by the alien hand.
• Alien hand is a rarely diagnosed disorder following brain illness that involves complex, goal-directed movement of 1 hand for which the patient lacks conscious intention.
• The disorder can be mistaken for psychiatric illness and can greatly trouble patients.
• Consistently successful treatments have not been developed.
• The clinician’s recognition of the characteristic presentation of the disorder could help to reduce the patient’s anxiety.
Historical note and terminology
Alien hand syndrome is not consistently or precisely defined. It describes goal-directed activity by 1 hand that is not voluntarily mediated. The patient is unable to explain the source of such movement and may consider the limb to move as if it had a mind of its own. It has been proposed that alien hand should be strictly defined as involuntary movements of the limb, whether appearing purposeful or not, and should be associated with a sense of loss of ownership (62). The key term is the “sense” of lack of ownership, without the patient expressly denying limb ownership, which can occur in other disorders.
Essentially, 3 kinds of behavior are covered by this term (46). The first 2 were described in a seminal paper. The first consists of repetitive involuntary grasping. Beginning in 1900, Liepmann drew attention to the unilateral, disinhibited grasp reflex to tactile stimulation after cerebral injury (Liepmann 1905), although this phenomenon had been described by Kaiser as early as 1897 (118). Liepmann's detailed descriptions of disinhibited grasp reflex and unilateral apraxia quickly inspired other German investigators to contribute their own observations of acquired complex movement disorders. Among them, Van Vleuten reported a patient with a left hemisphere brain tumor that had invaded the corpus callosum (128). The patient repeatedly grasped and put down an object with his right hand, apparently unintentionally. Goldstein first connoted the "alien" quality of unilateral repetitive grasping, the impression that an alternate entity is responsible for the behavior (56). His patient complained, "There must be an evil spirit in the hand!" In succeeding years, such behavior or other phenomena that suggested disinhibited, complex, and seemingly autonomous movements became formally labeled by terms that included, "pseudospontaneous movements" (132), Nachgreifen ("after-grasping") (118), "magnetic apraxia" (38), “manual grasping behavior” (87), the "groping-grasping reaction" (93), “visual groping” (134), and tactile mitgehen (manual pursuit movement) (48).
The second behavior covered by the term “alien hand syndrome” involves unilateral goal-directed limb movements that are contrary to the individual's intention and not accounted for by repetitious grasping or unilateral apraxia. Van Vleuten's patient appears to have been the earliest reported instance of this condition (128). In this case, the patient's left hand was not only apraxic but also performed markedly incorrect actions, such as touching his right hand instead of his nose, despite his understanding the command, and failing to move when commanded. Self-oppositional behavior, wherein 1 limb counteracts the declared or consciously intended action of the other limb, was often noted after complete or partial surgical division of the corpus callosum (callosotomy) to treat refractory epilepsy (129; 119). Akelaitis termed such behavior "diagonistic dyspraxia" (01). Brion and Jedynak coined the term la main étrangère (the foreign hand) to describe diverse behaviors in patients with callosal tumors that included either the failure to recognize self-ownership of the limb or the absence of self-control over the limb's goal-directed actions (19). In either case, the disturbance conveyed the impression of an alternative, silent, simultaneously coexisting "self" governing 1 side of the body, contrary to the bodily awareness and control that could be accessed introspectively. Of these 2 disturbances, the former is better termed “somatoparaphrenia” (72) or “asomatognosia” (125) and is usually associated with hemianesthesia.
Self-oppositional activity was also termed "intermanual conflict" by Bogen (15); he introduced the English term "alien hand," a translation of Brion and Jedynak's la main étrangère. Bogen intended "alien hand" to indicate a milder state of intermanual conflict among patients with surgical callosal lesions, wherein the individual finds 1 hand strange or uncooperative. Goldberg and colleagues applied this term to stroke patients with intermanual conflict, 1 of whom also had disinhibited groping (55). From this point onward, "alien hand" came to describe these 2 different motor disorders: (1) disinhibited groping and (2) self-opposition. However, investigators have not exercised restraint when reporting involuntary movements or postures in their patients. Thus, "alien hand" has been extended to include non-goal-directed, involuntary tonic posturing (20; 69; 117), even though the patient may not indicate any sort of alien quality (06). An “alien leg” counterpart to such activity also has been reported (68). Nonspecific epileptic movements that are associated with feelings of loss of ownership for the limb have also been reported as “alien limb” (14). These unfortunate corruptions of the term complicate its usefulness.
Della Sala and colleagues proposed "anarchic hand" as an alternative term for self-conflicting limb activity (34) because afflicted patients do not consider the limb itself to be alien, and also to provide a stricter definition than that intended by "alien hand." This term has become more widely used in recent years.
The third behavior describes intermittent unintended levitation, posturing, or lack of voluntary movement of 1 limb, with or without more complex phenomena or indication that the patient regards the behavior as unintended. This may follow stroke but is most often described in corticobasal syndrome (58; 28). Phenomena consistent with this form of alien hand have been reported since corticobasal syndrome was identified as a distinct disorder (111).
Despite the substantial diversity among these disorders, "alien hand" has become the preferred term for these disparate disturbances of motor self-control. This is regrettable because different pathophysiological mechanisms probably underlie the diverse behaviors in alien hand. Considering the wide variety of acquired disorders of voluntary movement, what constitutes or does not constitute alien hand seems to have been arbitrarily decided.