| Alien hand syndrome | |
|---|---|
| Other names | AHS; alien limb syndrome; ALS; Dr. Strangelove syndrome |
| Specialty | Psychiatry, Neurology |
Alien hand syndrome (AHS) or Dr. Strangelove syndrome is a category of conditions in which a person experiences their limbs acting seemingly on their own, without conscious control over the actions. There are a variety of clinical conditions that fall under this category, which most commonly affects the left hand. There are many similar terms for the various forms of the condition, but they are often used inappropriately. 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 controllable hand to restrain the alien hand. While under normal circumstances, thought, as intent, and action can be assumed to be deeply mutually entangled, the occurrence of alien hand syndrome can be usefully conceptualized as a phenomenon reflecting a functional "disentanglement" between thought and action.
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 and epileptic psychosis, e.g., temporal lobe epilepsy. It also occurs in some cases after brain surgery, stroke, infection, tumor, aneurysm, migraine and specific degenerative brain conditions such as Alzheimer's disease, Corticobasal degeneration and Creutzfeldt–Jakob disease. Other areas of the brain that are associated with alien hand syndrome are the frontal, occipital, and parietal lobes.
Signs and symptoms
"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. 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.
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, James 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 his behavior in a general
social context, a condition referred to as "environmental dependency syndrome".
In order to deal with the alien hand, some patients engage in personification of the affected hand. Usually these names are negative in nature, from mild such as "cheeky" to malicious "monster from the moon".
For example, Doody and Jankovic described a patient who named her alien
hand "baby Joseph". When the hand engaged in playful, troublesome
activities such as pinching her nipples (akin to biting while nursing),
she would experience amusement and would instruct baby Joseph to "stop
being naughty".
Furthermore, Bogen suggested that certain personality characteristics,
such as a flamboyant personality, contribute to frequent personification
of the affected hand.
Neuroimaging and pathological research shows that the frontal lobe (in the frontal variant) and corpus callosum (in the callosal variant) are the most common anatomical lesions responsible for the alien hand syndrome. These areas are closely linked in terms of motor planning and its final pathways.
The callosal variant includes advanced willed motor acts by the
non-dominant hand, where patients frequently exhibit "intermanual
conflict" in which one hand acts at cross-purposes with the other "good
hand".
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." Another patient was observed to be buttoning up her blouse
with her controlled dominant hand while the alien non-dominant hand, at
the same time, was unbuttoning her blouse. The frontal variant most
often affects the dominant hand, but can affect either hand depending on
the lateralization of the damage to medial frontal cortex, and includes
grasp reflex, impulsive groping toward objects or/and tonic grasping
(i.e. difficulty in releasing grip).
In most cases, classic alien-hand signs derive from damage to the medial frontal cortex, accompanying damage to the corpus callosum. In these patients the main cause of damage is unilateral or bilateral infarction of cortex in the territory supplied by the anterior cerebral artery or associated arteries.
Oxygenated blood is supplied by the anterior cerebral artery to most
medial portions of the frontal lobes and to the anterior two-thirds of
the corpus callosum,
and infarction may consequently result in damage to multiple adjacent
locations in the brain in the supplied territory. As the medial frontal
lobe damage is often linked to lesions of the corpus callosum, frontal
variant cases may also present with callosal form signs. Cases of damage
restricted to the callosum however, tend not to show frontal alien-hand
signs.
Cause
The common emerging factor in alien hand syndrome is that the primary motor cortex controlling hand movement is isolated from premotor cortex influences but remains generally intact in its ability to execute movements of the hand.
A 2009 fMRI study looking at the temporal sequence of activation
of components of a cortical network associated with voluntary movement
in normal individuals demonstrated "an anterior-to-posterior temporal
gradient of activity from supplemental motor area through premotor and
motor cortices to the posterior parietal cortex". Therefore, with normal voluntary movement, the emergent sense of agency
appears to be associated with an orderly sequence of activation that
develops initially in the anteromedial frontal cortex in the vicinity of
the supplementary motor complex on the medial surface of the frontal
aspect of the hemisphere (including the supplementary motor area) prior
to activation of the primary motor cortex in the pre-central gyrus on
the lateral aspect of the hemisphere, when the hand movement is being
generated. Activation of the primary motor cortex, presumed to be
directly involved in the execution of the action via projections into
the corticospinal component of the pyramidal tracts, is then followed by activation of the posterior parietal cortex, possibly related to the receipt of recurrent or re-afferent somatosensory feedback generated from the periphery by the movement which would normally interact with the efference copy
transmitted from primary motor cortex to permit the movement to be
recognized as self-generated rather than imposed by an external force.
That is, the efference copy allows the recurrent afferent somatosensory
flow from the periphery associated with the self-generated movement to
be recognized as re-afference as distinct from ex-afference.
Failure of this mechanism may lead to a failure to distinguish between
self-generated and externally generated movement of the limb. This
anomalous situation in which re-afference from a self-generated movement
is mistakenly registered as ex-afference due to a failure to generate
and successfully transmit an efference copy to sensory cortex, could
readily lead to the interpretation that what is in actuality a
self-generated movement has been produced by an external force as a
result of the failure to develop a sense of agency in association with
emergence of the self-generated movement (see below for a more detailed
discussion).
A 2007 fMRI study examining the difference in functional brain
activation patterns associated with alien as compared to non-alien
"volitional" movement in a patient with alien hand syndrome found that
alien movement involved anomalous isolated activation of the
primary motor cortex in the damaged hemisphere contralateral to the
alien hand, while non-alien movement involved the normal process of
activation described in the preceding paragraph in which primary motor
cortex in the intact hemisphere activates in concert with frontal
premotor cortex and posterior parietal cortex presumably involved in a
normal cortical network generating premotor influences on the primary
motor cortex along with immediate post-motor re-afferent activation of
the posterior parietal cortex.
Combining these two fMRI studies, one could hypothesize that the
alien behavior that is unaccompanied by a sense of agency emerges due to
autonomous activity in the primary motor cortex acting independently of
premotor cortex
pre-activating influences that would normally be associated with the
emergence of a sense of agency linked to the execution of the action.
As noted above, these ideas can also be linked to the concept of efference copy and re-afference,
where efference copy is a signal postulated to be directed from
premotor cortex (activated normally in the process associated with
emergence of an internally generated movement) over to somatosensory
cortex of the parietal region, in advance of the arrival of the
"re-afferent" input generated from the moving limb, that is, the
afferent return from the moving limb associated with the self-generated
movement produced. It is generally thought that a movement is
recognized as internally generated when the efference copy signal
effectively "cancels out" the re-afference. The afferent return from
the limb is effectively correlated with the efference copy signal so
that the re-afference can be recognized as such and distinguished from
"ex-afference", which would be afferent return from the limb produced by
an externally imposed force. When the efference copy is no longer
normally generated, then the afferent return from the limb associated
with the self-generated movement is mis-perceived as externally produced
"ex-afference" since it is no longer correlated with or canceled out by
the efference copy. As a result, the development of the sense that a
movement is not internally generated even though it actually is (i.e.
the failure of the sense of agency to emerge in conjunction with the
movement), could indicate a failure of the generation of the efference
copy signal associated with the normal premotor process through which
the movement is prepared for execution.
Since there is no disturbance of the sense of ownership of the limb (a concept discussed in the Wikipedia entry on sense of agency)
in this situation, and there is no clearly apparent physically
ostensible explanation for how the owned limb could be moving in a
purposive manner without an associated sense of agency, effectively
through its own power, a cognitive dissonance
is created which may be resolved through the assumption that the
goal-directed limb movement is being directed by an "alien"
unidentifiable external force with the capacity for directing
goal-directed actions of one's own limb.
Disconnection
It
is theorized that alien hand syndrome results when disconnection occurs
between different parts of the brain that are engaged in different
aspects of the control of bodily movement.
As a result, different regions of the brain are able to command bodily
movements, but cannot generate a conscious feeling of self-control over
these movements. As a result, the "sense of agency" that is normally
associated with voluntary movement is impaired or lost. There is a
dissociation between the process associated with the actual execution of
the physical movements of the limb and the process that produces an
internal sense of voluntary control over the movements, with this latter
process thus normally creating the internal conscious sensation that
the movements are being internally initiated, controlled and produced by
an active self.
Recent studies have examined the neural correlates of emergence of the sense of agency under normal circumstances.
This appears to involve consistent congruence between what is being
produced through efferent outflow to the musculature of the body, and
what is being sensed as the presumed product in the periphery of this
efferent command signal. In alien hand syndrome, the neural mechanisms
involved in establishing that this congruence has occurred may be
impaired. This may involve an abnormality in the brain mechanism that
differentiates between "re-afference" (i.e., the return of kinesthetic
sensation from the self-generated "active" limb movement) and
"ex-afference" (i.e., kinesthetic sensation generated from an externally
produced 'passive' limb movement in which an active self does not
participate). This brain mechanism is proposed to involve the
production of a parallel "efference copy" signal that is sent directly
to the somatic sensory regions and is transformed into a "corollary
discharge", an expected afferent signal from the periphery that would
result from the performance driven by the issued efferent signal. The
correlation of the corollary discharge signal with the actual afferent
signal returned from the periphery can then be used to determine if, in
fact, the intended action occurred as expected. When the sensed result
of the action is congruent with the predicted result, then the action
can be labelled as self-generated and associated with an emergent sense
of agency.
If, however, the neural mechanisms involved in establishing this
sensorimotor linkage associated with self-generated action are faulty,
it would be expected that the sense of agency with action would not
develop as discussed in the previous section.
Loss of inhibitions
One
theory posed to explain these phenomena proposes that the brain has
separable neural "premotor" or "agency" systems for managing the process
of transforming intentions into overt action.
An anteromedial frontal premotor system is engaged in the process of
directing exploratory actions based on "internal" drive by releasing or
reducing inhibitory control over such actions.
A recent paper reporting on neuronal unit recording in the medial
frontal cortex in human subjects showed a clear pre-activation of
neurons identified in this area up to several hundred milliseconds prior
to the onset of an overt self-generated finger movement and the authors
were able to develop a computational model whereby volition emerges
once a change in internally generated firing rate of neuronal assemblies
in this part of the brain crossed a threshold.
Damage to this anteromedial premotor system produces disinhibition and
release of such exploratory and object acquisition actions which then
occur autonomously. A posterolateral temporo-parieto-occipital premotor
system has a similar inhibitory control over actions that withdraw from
environmental stimuli as well as the ability to excite actions that are
contingent upon and driven by external stimulation, as distinct from
internal drive. These two intrahemispheric systems, each of which
activates an opposing cortical "tropism", interact through mutual
inhibition that maintains a dynamic balance between approaching toward
(i.e. with "intent-to-capture" in which contact with and grasping onto
the attended object is sought) versus withdrawing from (i.e. with
"intent-to-escape" in which distancing from the attended object is
sought) environmental stimuli in the behavior of the contralateral
limbs. Together, these two intrahemispheric agency systems form an integrated trans-hemispheric agency system.
When the anteromedial frontal "escape" system is damaged,
involuntary but purposive movements of an exploratory reach-and-grasp
nature—what Denny-Brown referred to as a positive cortical tropism—are released in the contralateral limb. This is referred to as a positive
cortical tropism because eliciting sensory stimuli, such as would
result from tactile contact on the volar aspect of the fingers and palm
of the hand, are linked to the activation of movement that increases or
enhances the eliciting stimulation through a positive feedback
connection (see discussion above in section entitled "Parietal and
Occipital Lobes").
When the posterolateral parieto-occipital "approach" system is
damaged, involuntary purposive movements of a release-and-retract
nature, such as levitation and instinctive avoidance – what Denny-Brown
referred to as a negative cortical tropism – are released in the contralateral limb. This is referred to as a negative
cortical tropism because eliciting sensory stimuli, such as would
result from tactile contact on the volar aspect of the fingers and palm
of the hand, are linked to the activation of movement that reduces or
eliminates the eliciting stimulation through a negative feedback
connection (see discussion above in section entitled "Parietal and
Occipital Lobes").
Each intrahemispheric agency system has the potential capability
of acting autonomously in its control over the contralateral limb
although unitary integrative control of the two hands is maintained
through interhemispheric communication between these systems via the
projections traversing the corpus callosum at the cortical level and other interhemispheric commissures linking the two hemispheres at the subcortical level.
Disconnection of hemispheres due to injury
One
major difference between the two hemispheres is the direct connection
between the agency system of the dominant hemisphere and the encoding
system based primarily in the dominant hemisphere that links action to
its production and through to its interpretation with language and
language-encoded thought. The overarching unitary conscious agent that
emerges in the intact brain is based primarily in the dominant
hemisphere and is closely connected to the organization of language
capacity. It is proposed that while relational action in the form of
embodied inter-subjective behavior
precedes linguistic capacity during infant development, a process
ensues through the course of development through which linguistic
constructs are linked to action elements in order to produce a
language-based encoding of action-oriented knowledge.
When there is a major disconnection between the two hemispheres
resulting from callosal injury, the language-linked dominant hemisphere
agent which maintains its primary control over the dominant limb loses,
to some degree, its direct and linked control over the separate "agent"
based in the nondominant hemisphere, and the nondominant limb, which had
been previously responsive and "obedient" to the dominant conscious
agent. The possibility of purposeful action occurring outside of the
realm of influence of the conscious dominant agent can occur and the
basic assumption that both hands are controlled through and subject to
the dominant agent is proven incorrect. The sense of agency
that would normally arise from movement of the nondominant limb now no
longer develops, or, at least, is no longer accessible to consciousness.
A new explanatory narrative for understanding the situation in which
the now inaccessible nondominant hemisphere based agent is capable of
activating the nondominant limb is necessitated.
Under such circumstances, the two separated agents can control
simultaneous actions in the two limbs that are directed at opposing
purposes although the dominant hand remains linked to the dominant
consciously accessible language-linked agent and is viewed as continuing
to be under "conscious control" and obedient to conscious will and
intent as accessible through thought, while the nondominant hand,
directed by an essentially non-verbal agent whose intent can only be
inferred by the dominant agent after the fact, is no longer "tied in"
and subject to the dominant agent and is thus identified by the
conscious language-based dominant agent as having a separate and
inaccessible alien agency and associated existence. This theory would
explain the emergence of alien behavior in the nondominant limb and
intermanual conflict between the two limbs in the presence of damage to
the corpus callosum.
The distinct anteromedial, frontal, and posterolateral
temporo-parieto-occipital variants of the alien hand syndrome would be
explained by selective injury to either the frontal or the posterior
components of the agency systems within a particular hemisphere, with
the relevant and specific form of alien behavior developing in the limb
contralateral to the damaged hemisphere.
Diagnosis
Corpus callosum
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).
In "the callosal variant", the patient's hand counteracts
voluntary actions performed by the other, "good" hand. Two phenomena
that are often found in patients with callosal alien hand are agonistic dyspraxia and diagonistic dyspraxia.
Agonistic dyspraxia involves compulsive automatic execution of
motor commands by one hand when the patient is asked to perform
movements with the other hand. For example, when a patient with callosal
damage was instructed to pull a chair forward, the affected hand would
decisively and impulsively push the chair backwards.
Agonistic dyspraxia can thus be viewed as an involuntary competitive
interaction between the two hands directed toward completion of a
desired act in which the affected hand competes with the unaffected hand
to complete a purposive act originally intended to be performed by the
unaffected hand.
Diagonistic dyspraxia, on the other hand, involves a conflict
between the desired act in which the unaffected hand has been engaged
and the interfering action of the affected hand which works to oppose
the purpose of the desired act intended to be performed by the
unaffected hand. For instance, when Akelaitis's patients underwent
surgery to the corpus callosum to reduce epileptic seizures, one
patient's left alien hand would frequently interfere with the right
hand. For instance, while trying to turn over to the next page with the
right hand, his left hand would try to close the book.
In another case of callosal alien hand, the patient did not
suffer from intermanual conflict between the hands but rather from a
symptom characterized by involuntary mirror movements of the affected
hand.
When the patient was asked to perform movements with one hand, the
other hand would involuntarily perform a mirror image movement which
continued even when the involuntary movement was brought to the
attention of the patient, and the patient was asked to restrain the
mirrored movement. The patient suffered from a ruptured aneurysm near the anterior cerebral artery,
which resulted in the right hand being mirrored by the left hand. The
patient described the left hand as frequently interfering and taking
over anything the patient tried to do with the right hand. For instance,
when trying to grasp a glass of water with the right hand with a right
side approach, the left hand would involuntary reach out and grasp hold
of the glass through a left side approach.
More recently, Geschwind et al. described the case of a woman who suffered severe coronary heart disease.
One week after undergoing coronary artery bypass grafting, she noticed
that her left hand started to "live a life of its own". It would
unbutton her gown, try to choke her while asleep and would automatically
fight with the right hand to answer the phone. She had to physically
restrain the affected hand with the right hand to prevent injury, a
behavior which has been termed "self-restriction". The left hand also
showed signs of severe ideomotor apraxia.
It was able to mimic actions but only with the help of mirror movements
executed by the right hand (enabling synkinesis). Using magnetic resonance imaging (MRI), Geschwind et al. found damage to the posterior half of the callosal body, sparing the anterior half and the splenium extending slightly into the white matter underlying the right cingulate cortex.
Park et al. also described two cases of infarction as the origin
of alien hand symptoms. Both individuals had suffered an infarction of
the anterior cerebral artery (ACA). One individual, a 72 year-old male,
had difficulty controlling his hands, as they often moved involuntarily,
despite his trying to stabilize them. Furthermore, he often could not
let go of objects after grasping them with his palms. The other
individual, a 47 year-old female who suffered an ACA in a different
location of the artery, complained that her left hand would move on its
own and she could not control its movements. Her left hand could also
sense when her right hand was holding an object and would involuntarily,
forcibly take the object out of her right hand.
Frontal lobe
Unilateral injury to the medial aspect of 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 has been acquired and 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 (also referred to as tonic grasping or the "instinctive grasp
reaction"). Some (for example, the neurologist Derek Denny-Brown) have referred to this behavior as "magnetic apraxia"
Goldberg and Bloom described a woman who suffered a large cerebral infarction
of the medial surface of the left frontal lobe in the territory of the
left anterior cerebral artery which left her with the frontal variant of
the alien hand involving the right hand.
There were no signs of callosal disconnection nor was there evidence of
any callosal damage. The patient displayed frequent grasp reflexes; her
right hand would reach out and grab objects without releasing them. In
regards to tonic grasping, the more the patient tried to let go of the
object, the more the grip of the object tightened. With focused effort
the patient was able to let go of the object, but if distracted, the
behaviour would re-commence. The patient could also forcibly release the
grasped object by peeling her fingers away from contact with the object
using the intact left hand. Additionally, the hand would scratch at the
patient's leg to the extent that an orthotic device was required to
prevent injury.
Another patient reported not only tonic grasping towards objects
nearby, but the alien hand would take hold of the patient's penis and
engage in public masturbation.
Parietal and occipital lobes
A distinct "posterior variant" form of alien hand syndrome is associated with damage to the posterolateral 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 sustained
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. In the frontal variant, tactile contact on the
ventral surface of the palm and fingers facilitates finger flexion and
grasp of the object through a positive feedback loop (i.e. the stimulus
generates movement that reinforces, strengthens and sustains the
triggering stimulation).
In contrast, in the posterior variant, tactile contact on the
ventral surface of the palm and fingers is actively avoided through
facilitation of extension of the fingers and withdrawal of the palm in a
negative feedback loop (i.e. the stimulus, and even anticipation of
stimulation of the palmar surface of the hand, generates movement of the
palm and fingers that reduces and effectively counteracts and
eliminates the triggering stimulation, or, in the case of anticipated
palmar contact, decreases the likelihood of such contact). Alien
movements in the posterior variant of the syndrome also tend to be less
coordinated and show a coarse ataxic motion during active movement that
is generally not observed in the frontal form of the condition. This is
generally thought to be due to an optic form of ataxia since it is
facilitated by the visual presence of an object with visual attention
directed toward the object. The apparent instability could be due to an
unstable interaction between the tactile avoidance tendency biasing
toward withdrawal from the object, and the visually based acquisition
bias tendency pushing toward an approach to the object.
The alien limb in the posterior variant of the syndrome may be
seen to "levitate" upward into the air withdrawing away from contact
surfaces through the activation of anti-gravity musculature. Alien hand
movement in the posterior variant may show a typical posture, sometimes
referred to as a "parietal hand" or the "instinctive avoidance reaction"
(a term introduced by neurologist Derek Denny-Brown
as an inverse form of the "magnetic apraxia" seen in the frontal
variant, as noted above), in which the digits move into a highly
extended position with active extension of the interphalangeal joints of
the digits and hyper-extension of the metacarpophalangeal joints, and
the palmar surface of the hand is actively pulled back away from
approaching objects or up and away from supporting surfaces. The
"alien" movements, however, remain purposeful and goal-directed, a point
which clearly differentiates these movements from other disorganized
non-purposeful forms of involuntary limb movement (e.g. athetosis, chorea, or myoclonus).
Similarities between frontal and posterior variants
In
both the frontal and the posterior variants 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. In
both of these variants of alien hand syndrome, the alien hand emerges in
the hand contralateral to the damaged hemisphere.
Treatment
There is no cure for the alien hand syndrome.
However, the symptoms can be reduced and managed to some degree by
keeping the alien hand occupied and involved in a task, for example by
giving it an object to hold in its grasp. Specific learned tasks can
restore voluntary control of the hand to a significant degree. One
patient with the "frontal" form of alien hand who would reach out to
grasp onto different objects (e.g., door handles) as he was walking was
given a cane to hold in the alien hand while walking, even though he
really did not need a cane for its usual purpose of assisting with
balance and facilitating ambulation. 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. Other
techniques proven to be effective includes; wedging the hand between the
legs or slapping it; warm water application and visual or tactile
contact. Additionally, Wu et al. found that an irritating alarm activated by biofeedback reduced the time the alien hand held an 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. Actually, when AHS originates
from focal injury of acute onset, recovery usually occurs within a year. One theory is that neuroplasticity
in the bihemispheric and subcortical brain systems involved in
voluntary movement production can serve to re-establish the connection
between the executive production process and the internal
self-generation and registration process. Exactly how this may occur is
not well understood, but a process of gradual recovery from alien hand
syndrome when the damage is confined to a single cerebral hemisphere has
been reported.
In some instances, patients may resort to constraining the wayward,
undesirable and sometimes embarrassing actions of the impaired hand by
voluntarily grasping onto the forearm of the impaired hand using the
intact hand. This observed behavior has been termed "self-restriction"
or "self-grasping".
In another approach, the 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. It is possible that
some of this training produces a re-organization of premotor systems
within the damaged hemisphere, or, alternatively, that ipsilateral control of the limb from the intact hemisphere may be expanded.
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. Other patients have reported using an orthotic device to
restrict perseverative grasping or restraining the alien hand by securing it to the bed pole.
Of course, this can limit the degree to which the hand can participate
in addressing functional goals for the patient and may be considered to
be an unjustifiable restraint.
Theoretically, this approach could slow down the process through
which voluntary control of the hand is restored if the neuroplasticity
that underlies recovery involves the recurrent exercise of voluntary
will to control the actions of the hand in a functional context and the
associated experiential reinforcement through successful willful
suppression of the alien behavior.
History
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.
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. When the left hand grasped an object, she could
not voluntarily release it. The senses of touch and proprioception
of the left side were impaired. The left hand would make spontaneous
movements, such as wiping the face or rubbing the eyes, but these were
relatively infrequent. With significant effort, she was able to move her
left arm in response to spoken command, but conscious movements were
slower or less precise than similar involuntary motions.
Goldstein developed a "doctrine of motor apraxia" in which he
discussed the generation of voluntary action and proposed a brain
structure for temporal and spatial cognition, will
and other higher cognitive processes. Goldstein maintained that a
structure conceptually organizing both the body and external space was
necessary for object perception as well as for voluntary action on
external objects.
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".
In popular culture
- In Stanley Kubrick's 1964 film Dr. Strangelove, the eponymous character played by Peter Sellers apparently suffers from alien hand syndrome, as he can't stop himself from doing the Nazi salute. "Dr. Strangelove syndrome" was suggested as the official name for AHS. This was not approved, though it is sometimes used as an alternative name.
- In the 1999 American horror comedy film Idle Hands, the teenage boy protagonist finds out that his right hand has become possessed and is responsible for killing his parents and harming others.
- In the House episode "Both Sides Now", a patient suffers from alien hand syndrome.
- An episode of Dark Matters: Twisted But True—a documentary show on Discovery Science—described alien hand syndrome and traced its history.
- The 2017 Indian Tamil dark comedy film Peechankai is about a person who suffers from AHS.
- In Season 2 of Scream Queens, Dr. Brock Holt appears to suffer from alien hand syndrome.
- An episode of the NPR show Invisibilia centers on a lady who developed alien hand syndrome after brain surgery.
- The 2018 Indian Kannada Comedy film Sankashta Kara Ganapathi is about a cartoonist suffering from AHS.
