Search

Alien hand syndrome is a rare condition associated with lesions of the corpus callosum and of the supplementary motor area, which can be caused by ruptured cerebral aneurysms. We present a novel case of a patient with a subarachnoid haemorrhage from an aneurysm of the anterior communicating artery who developed alien hand syndrome and intermanual conflict. In addition, we performed a systematic literature search and evaluated data on clinical presentation, treatment and radiological findings from relevant papers. To date, 17 cases of alien hand syndrome in aneurysmatic subarachnoid haemorrhage have been reported. Aneurysms of the anterior communicating artery were the most common origin of subarachnoid haemorrhage (10/17), followed by pericallosal artery aneurysms (7/10). The prognosis appears to be favourable; however, damage to the supplementary motor area during treatment should be avoided to keep symptoms minimal.

Background Alien hand syndrome (AHS) is a disabling condition in which one hand behaves in a way that the person finds "alien". This feeling of alienation is related to the occurrence of movements of the respective hand performed without or against conscious intention. Most information on AHS stems from single case observations in patients with frontal, callosal, or parietal brain damage. Methods Retrospective analysis of distinctive clinical features of three out of 18 epilepsy patients who developed AHS with antagonistic movements of the left hand after corpus callosotomy (CC) (one anterior, two complete) for the control of epileptic seizures, particularly epileptic drop attacks (EDA). Results Remarkably, these three patients, two men and one woman, displayed atypical language dominance with a bilateral, left more than right hemisphere language representation in intracarotidal amobarbital testing before surgery. The overall additional distinctive feature of the target patients was genuine left-handedness, with writing retrained to right-handedness in two patients. After surgery the left hands became alien. The problem was permanent, despite strategies for compensation. Conclusion From this observation we suggest that under the conditions of dissociation of language and motor dominance, loss of both intentional control of contralateral action and physiological inhibition of antagonistic movements lead to post-callosotomy alien-hand-like motor phenomena. The dissociation pattern posing this risk seems rare but needs to be considered when evaluating candidates for callosotomy.

A 69-year-old woman presented with a cortical hand syndrome progressing over several weeks. MRI brain showed characteristic appearances of progressive multifocal leukoencephalopathy (PML), confirmed by detection of the JC virus in CSF, despite the absence of any evidence of immunosuppression. Treatment with mirtazapine, mefloquine and cidofovir did not affect the progression of the disease, which was fatal within 7 months of presentation. This report adds to the small case literature that suggests that PML can occur in immunocompetent people, albeit extremely rarely.

Alien limb refers to movements that seem purposeful but are independent of patients’ reported intentions. Alien limb often co-occurs with apraxia in the corticobasal syndrome, and anatomical and phenomenological comparisons have led to the suggestion that alien limb and apraxia may be causally related as failures of goal-directed movements. Here, we characterised the nature of alien limb symptoms in patients with the corticobasal syndrome (n = 30) and their relationship to limb apraxia. Twenty-five patients with progressive supranuclear palsy Richardson syndrome served as a disease control group. Structured examinations of praxis, motor function, cognition and alien limb were undertaken in patients attending a regional specialist clinic. Twenty-eight patients with corticobasal syndrome (93%) demonstrated significant apraxia and this was often asymmetrical, with the left hand preferentially affected in 23/30 (77%) patients. Moreover, 25/30 (83%) patients reported one or more symptoms consistent with alien limb. The range of these phenomena was broad, including changes in the sense of ownership and control as well as unwanted movements. Regression analyses showed no significant association between the severity of limb apraxia and either the occurrence of an alien limb or the number of alien limb phenomena reported. Bayesian estimation showed a low probability for a positive association between alien limb and apraxia, suggesting that alien limb phenomena are not likely to be related to severity apraxia. Our results shed light on the phenomenology of these disabling and as yet untreatable clinical features, with relevance to theoretical models of voluntary action.

OBJECTIVE Perirolandic atrophy occurs in corticobasal syndrome (CBS) but is not specific versus progressive supranuclear palsy (PSP). There is heterogeneity in the locations of atrophy outside the perirolandic cortex and it remains unknown why atrophy in different locations would cause the same CBS-specific symptoms. In prior work, we used a wiring diagram of the brain called the human connectome to localize lesion-induced disorders to symptom-specific brain networks. Here, we use a similar technique termed "atrophy network mapping" to localize single-subject atrophy maps to symptom-specific brain networks. METHODS Single-subject atrophy maps were generated by comparing cortical thickness in patients with CBS versus controls. Next, we performed seed-based functional connectivity using a large normative connectome to determine brain regions functionally connected to each patient's atrophied locations. RESULTS Patients with CBS had perirolandic atrophy versus controls at the group level, but locations of atrophy in CBS were heterogeneous outside of the perirolandic cortex at the single-subject level (mean spatial correlation = 0.04). In contrast, atrophy occurred in locations functionally connected to the perirolandic cortex in all patients with CBS (spatial correlation = 0.66). Compared with PSP, patients with CBS had atrophy connected to a network of higher-order sensorimotor regions beyond perirolandic cortex, matching a CBS atrophy network from a recent meta-analysis. Finally, atrophy network mapping identified a symptom-specific network for alien limb, matching a lesion-induced alien limb network and a network associated with agency in healthy subjects. INTERPRETATION We identified a syndrome-specific network for CBS and symptom-specific network for alien limb using single-subject atrophy maps and the human connectome. ANN NEUROL 2020;88:1118-1131.

Alien limb syndrome following stroke within the territory of the posterior cerebral artery is exceedingly rare. A right-handed female experienced left homonymous hemianopia, visuospatial neglect, and proprioceptive loss of her left hemi-body. She experienced unintended, involuntary movements of her left arm and hand, which interfered with and disturbed motor actions of daily life performed with her right upper limb. There was no denial of ownership, but she interpreted movements of her left upper limb to be annoying, out of her will and unwanted. The alien limb phenomenon improved in parallel with improvement of proprioceptive loss over a 12-week of in-patient rehabilitation. A recently proposed theoretical concept of the alien limb phenomenon after posterior artery stroke is discussed.

A 94-year-old patient developed the alien hand syndrome in the left (nondominant) hand following an ischemic stroke of the right parietotemporal lobe (including postcentral gyrus, superior and inferior parietal lobule) due to an occlusion of the posterior division of the right middle cerebral artery.

We report the case of a 73-year-old right-handed female with a right parietal cerebral infarction and presented symptoms that were challenging to differentiate between alien hand sign (AHS) and sensory ataxia. She presented to our emergency department with chief complaints of abnormal involuntary movements and a feeling of foreignness on her left upper limb. The first neurological examination revealed left spatial neglect, left-side sensory impairment that included superficial and deep sensations, left limb-kinetic apraxia, and left limb ataxia. Furthermore, her symptoms and complaints had characteristics of AHS that includes a sensation that her left upper limb dose not belong to herself and an abnormal behavior of left hand that is contrary to her own intent. Brain MRI revealed an acute cerebral infarction confined to the right postcentral gyrus. This case highlights that sensory ataxia due to the disturbance of deep sensation might present symptoms similar to AHS. Previous studies suggested the involvement of the disturbance of somatosensory pathway in posterior-variant AHS. Therefore, a precise distinction between AHS and sensory ataxia, especially in posterior-variant AHS, is imperative to avoid confusion regarding the term "alien hand sign."

Background Alien Hand Syndrome (AHS) is an uncontrollable, involuntary, but in appearance, purposeful motor control disorder of the upper extremity. Case report A 42-year-old male patient was admitted to our clinic complaining of involuntary motor activity in his right hand. He had a previous history of migraine with visual aura. The uncontrollable motor control disorder was compatible with Alien Hand Syndrome, which was appearing immediately after the visual aura and before the beginning of headache. Conclusion Alien Hand Syndrome is usually observed with anterior cerebral artery infarction, midline tumors, trauma and several neurodegenerative diseases, but is rarely seen in paroxysmal conditions such as migraine with aura.

Anarchic hand syndrome (AHS) is characterized by goal-directed movements performed without volitional control (agency). Different AHS subtypes have been identified; however, few studies have examined the posterior subtype. We report a case of AHS following right-hemisphere parietal damage, with left-sided somatosensory and proprioceptive impairment. Agency was examined for nonanarchic (volitional) movements performed using the anarchic hand. The patient experienced abnormal agency for movements whether motor intention and visual feedback were congruent or incongruent, but not when intention was absent (passive movement). Findings suggest a general disturbance of veridical motor awareness and agency in this case of parietal AHS.

Ischemic lesions within the territory of the anterior cerebral artery present with a variety of clinical signs and symptoms. Among these, frontal alien hand syndrome is rare and easily overlooked in the acute clinical setting, but significantly impacts on functional activities of daily life. Given its rareness, very little is known about its long-term outcome. To shade some more light onto this issue, clinical presentation, course of rehabilitation and outcome of two illustrative cases of frontal alien hand syndrome following anterior cerebral artery stroke are presented. Within seven and nine months from symptom onset, respectively, the clinical symptoms of frontal alien hand had resolved completely in both cases. We conclude that frontal alien hand syndrome has a favourable long-term outcome.

A 47-year-old man developed sudden-onset abulia and alien hand syndrome (AHS). MRI revealed bilateral ischemic injury within anterior cerebral artery territory (a complex bilateral corpus callosum infarction1) due to obstruction of a variant bihemispheric A2 branch by a thrombus (figures 1 and 2), also demonstrated on 3D volume-rendered CT angiography (figure 2). The finding of lower-limb deep venous thrombosis in a patient with right-to-left interatrial shunt accounted for the case, given workup was otherwise unremarkable.

The Video NeuroImage by Debray and Demeestere1 is a good demonstration of the callosal alien hand variant, typified by intermanual conflict. This is in contrast to the frontal alien hand variant, where there is compulsive grasping and grabbing, but without fighting over control of an object.

Corticobasal degeneration (CBD) may be expressed as an atypical parkinsonism with a mean disease survival of about 7 years,(1) the shortest reported survival being 24 months.(2) We report a patient with corticobasal syndrome (CBS) and pathology-confirmed CBD whose 10-month course was manifested as a frontal alien hand evolving into agrypnia excitata.

It has been shown that combinations of visual, tactile, and proprioceptive manipulations in healthy subjects may elicit illusory feelings of embodiment (the rubber hand illusion and the somatic rubber hand illusion). We report a case of alien hand syndrome in which the alien hand interacted with the somatic rubber hand illusion to provoke a very strong movement of the alien hand. This effect could be reliably replicated at every application of the experimental procedure. Thus, the illusion seemed to wake up the alien hand. The results demonstrate that the alien hand syndrome can be affected by experimentally induced bodily illusions, which are based on the manipulation of touch and proprioceptive information.

Anarchic hand syndrome (AHS) is a rare disorder characterized by unwilled, but seemingly purposeful movements of the affected upper limb which are perceived by the patients not to be under their control. It often interferes with goal-directed movements and bimanual tasks. At present there is no effective method of treatment of AHS. We report here a case of AHS following resection of a frontal lobe tumor and describe its effects on the patient's functional activities. The patient used avoidance behavior and mental concentration to overcome the disabling effect of AHS. These strategies appear to be useful in the management of AHS.

Alien hand syndrome (AHS) is a rare disorder of involuntary limb movement together with a sense of loss of limb ownership. It most commonly affects the hand, but can occur in the leg. The anterior (frontal, callosal) and posterior variants are recognized, with distinguishing clinical features and anatomical lesions. Initial descriptions were attributed to stroke and neurosurgical operations, but neurodegenerative causes are now recognized as most common. Structural and functional imaging and clinical studies have implicated the supplementary motor area, pre-supplementary motor area, and their network connections in the frontal variant of AHS, and the inferior parietal lobule and connections in the posterior variant. Several theories are proposed to explain the pathophysiology. Herein, we review the literature to update advances in the understanding of the classification, pathophysiology, etiology, and treatment of AHS.

Alien hand syndrome is a rare neurological disorder characterized by involuntary and uncontrollable motor behaviour, usually of an arm or hand. The patient perceives the affected limb as alien, and may personify it. The case of a 61-year-old right-handed woman who developed right posterior AHS after ischaemic stroke in the left posterior cerebral artery territory is reported. Neuroimaging studies disclosed no frontal or parietal involvement, while a posterior thalamic lesion was detected. A possible role of the thalamus in the genesis of AHS is discussed.

Posterior alien hand syndrome is a new addition to a poorly understood group of movement disorders. Historically, anatomical lesions causing uncontrolled limb movement and a feeling of foreignness were found to be located in the corpus callosum or frontal lobe. Recent case reports, however, demonstrate the typical symptoms of alien hand syndrome with lesions located in the parietal/occipital lobes. Disturbance of normal function in these regions tends to produce less complex motor activity, such as hand levitation, along with a sensory component characterized by feeling of estrangement. We discuss a patient who presented with unusual symptoms following an outpatient procedure and was found to have posterior alien hand syndrome.

Seizures are relatively common in Alzheimer disease (AD) and other neurodegenerative disorders. To our knowledge, however, there have been no reports of seizures associated with corticobasal degeneration (CBD). We describe a patient with brain biopsy features suggestive of CBD whose course was complicated by complex partial seizures with secondary generalization. Thus, the occurrence of seizures in a patient with dementia should not exclude the diagnosis of CBD.

Background: “Anarchic hand” is a rare condition characterised by non-volitional, goal-directed movements of one arm. We report a case with analysis of structural and functional connectivity. Case presentation: A 15 year old girl developed intermittent symptoms of intermanual conflict or anarchic hand as a result of traumatic brain injury during which she sustained a callosal bleed. Resting-state fMRI and DTI tractography were performed at a stage when symptoms had largely resolved. Conclusion: Structural connectivity between homologous superior frontal areas and functional connectivity between homologous posterior cingulate areas were significantly reduced, which may have contributed to causation. Tractography demonstrated new indirect connections between supplementary motor areas via the cerebellum, which we propose contributed to symptom resolution.

Epilepsia partialis continua (EPC) is clinically defined as a syndrome of continuous focal jerking of a body part, usually a distal limb, occurring over hours, days, or even years. It is considered the status epilepticus equivalent of simple partial motor seizures. A 48-year-old right-handed man with a history of traumatic intracranial hemorrhage was admitted for right-sided hemiplegia and drowsiness after complex partial status epilepticus. An EEG showed periodic lateralized epileptiform discharges over the left hemisphere. Brain MRI revealed extensive multifocal encephalomalaciac changes in the left temporo-parieto-occpital lobe and both frontal lobes with some hemorrhagic residual change. After administration of a loading dose of intravenous phenytoin, his mental status returned to normal. However, his weakness only partially improved. [18F]Fluorodeoxyglucose PET (FDG-PET) demonstrated severe hypometabolism in the left cerebral hemisphere, including the basal ganglia and thalamus, with cerebellar diaschisis. At the 3-month follow-up, he complained of symptoms of alien hand phenomenon. Follow-up MRI revealed more extensive encephalomalaciac changes in previously noted regions with thinning of the posterior end of the body of the corpus callosum. Moreover, FDG-PET demonstrated persistent severe hypometabolism over the left cerebral hemisphere. We suggest that the alien hand phenomenon was a result of thinning of the corpus callosum related to EPC.

A pediatric patient with diagnosis of Parry-Romberg syndrome, or progressive hemifacial atrophy, presented with new-onset unilateral alien hand syndrome, which was attributed to focal progressive atrophy and gliosis in the contralateral thalamus observed on serial neuroimaging. This case illustrates not only the clinical-radiographic correlation between alien hand syndrome and contralateral thalamic lesion, but also involvement of deep gray structure in Parry-Romberg syndrome causing a rare movement disorder.

We discuss a patient who developed an "alien limb" on her right side after brain herniation. She reported feeling as though her arm movements were controlled by a stranger and displayed limb levitation and groping behaviors. She received 0.5 mg clonazepam b.i.d. This was followed by a limb levitation frequency reduction of 73%. Discontinuation and retrial of clonazepam verified this response. She suffered a psychotic episode that she attributed to clonazepam. Clonazepam was discontinued. She received botulinum toxin injections to her arm that reduced her limb levitation by 84%. This is the first report of response to medication in alien limb syndrome.

We present a 41-year-old man who experienced alien limb syndrome as a complication of treatment for recurrent Grade III oligodendroglioma of the right parietal lobe. Alien limb syndrome is a rare phenomenon in which a limb performs involuntary actions and the affected individual feels a sense of estrangement towards the limb. It occurs most commonly as a result of corticobasal syndrome, though a variety of other etiologies have been reported. It is rarely associated with focal lesions, such as stroke or tumors.

Disruption of motor control in the alien hand syndrome might result from a dissociation between intentions and sensory information. We hypothesized that voluntary motor control in this condition could improve by restoring the congruency between motor intentions and visual feedback. The present study shows that, in one patient with right alien hand syndrome, the use of a mirror box paradigm improved motor speed. We speculate that the visual feedback provided by the mirror increases the sense of congruence between intention and sensory feedback, leading to motor improvement.

Parry-Romberg syndrome (PRS) is a rare condition characterised by progressive hemi-facial atrophy. Here we present a PRS case with alien-hand syndrome, which has not previously been described in adult onset disease. On the basis of the presumed auto-immune pathology of PRS we justify the treatment strategy we successfully used in this patient. A review of the literature was extensively done for understanding the history of alien hand sign over the years.

Alien limb phenomenon refers to involuntary motor activity of a limb in conjunction with the feeling of estrangement from that limb. Alien limb serves as a diagnostic feature of corticobasal syndrome. Our objective was to determine the differential diagnoses of alien limb and to determine the features in a large group of patients with the alien limb with different underlying etiologies. We searched the Mayo Clinic Medical Records Linkage system to identify patients with the diagnosis of alien limb seen between January 1, 1996, and July 11, 2011. One hundred and fifty patients with alien limb were identified. Twenty-two were followed in the Alzheimer's Disease Research Center. Etiologies of alien limb included corticobasal syndrome (n = 108), stroke (n = 14), Creutzfeldt Jakob disease (n = 9), hereditary diffuse leukoencephalopathy with spheroids (n = 5), tumor (n = 4), progressive multifocal leukoencephalopathy(n = 2), demyelinating disease (n = 2), progressive dementia not otherwise specified (n = 2), posterior reversible encephalopathy syndrome (n = 1), corpus callosotomy (n = 1), intracerebral hemorrhage (n = 1) and thalamic dementia (n = 1). Ten of 14 cerebrovascular cases were right hemisphere in origin. All cases involved the parietal lobe. Of the 44 patients with corticobasal syndrome from the Alzheimer's Disease Research Center cohort, 22 had alien limb, and 73 % had the alien limb affecting the left extremities. Left sided corticobasal syndrome was significantly associated with the presence of alien limb (p = 0.004). These findings support the notion that the alien limb phenomenon is partially related to damage underlying the parietal cortex, especially right parietal, disconnecting it from other cortical areas.

We report a patient who presented with callosal disconnection syndrome (CDS) and fiber disconnection on diffusion tensor tractography (DTT) after an infarct of the corpus callosum (CC). A 72-year-old woman presented with manifestations of CDS, including frontal alien hand syndrome (AHS), left agraphia, right hemiparesis, right somatosensory deficit, left neglect, and impaired visual recognition. DTT was performed for the evaluation of CC fibers, followed by comparison with DTT findings of normal subjects. DTT of the normal subject revealed bilateral extension of CC fibers to the frontal, parietal, and occipitotemporal cortices. By contrast, CC fibers of the patient revealed extensive disruption, with the exception of CC fibers passing through the anterior genu and the posterior splenium. The extensive disruption of CC fibers appears to explain the patient's various CDS symptoms. In brief, DTT could be useful for detection of CC lesions in patients with CDS.

A 26-year-old right-handed female presented with alien hand syndrome (AHS) secondary to corpus callosum (CC) hematoma. The patient had abnormal feelings in the left upper limb and exhibited intermanual conflict. Imaging studies demonstrated acute hemorrhage in the genu and body of the CC secondary to cerebral venous malformation. Callosal hemorrhage is usually caused by head trauma or a ruptured arteriovenous that extends beyond the CC. We report what may be the first case of AHS caused by callosal hemorrhage due to venous malformation.

Langerhans cell histiocytosis (LCH) with multiple organ involvement is a rare disorder in adults. Extrapituitary involvement of the central nervous system (CNS) is uncommon. We report the unusual case of a 55-year-old woman presenting with a left-sided hemiataxia-hemiparesis, left hemisensory loss and short-lasting episodes of an alien left hand due to lesions of the internal capsule and the right thalamus, extending into the mesencephalon associated with extensive surrounding edema, without pituitary involvement. The neuroradiological image suggested glioblastoma multiforme. Brain biopsy revealed inflammatory tissue and "pseudotumoral" multiple sclerosis was suspected. Biopsy of concomitant lung and bone lesions disclosed Langerhans cell histiocytosis. The treatment with pulsed steroids in association with mycophenolate mofetil led to a sustained, clinical neurological remission.

Here we present a patient with an isolated paracallosal brain lesion who exhibited behavioral changes associated with the corpus callosum syndrome (CCS) including features of the alien hand syndrome (AHS). The CCS is also known as the split-brain syndrome, the syndrome of hemisphere disconnection, the syndrome of brain bisection and the syndrome of the cerebral commissures. Because most reported cases of CCS were caused by tumors which extended beyond the corpus callosum (CC) and did not always induce a complete disconnection, there was much controversy about the role of the CC and the existence of a specific CCS. Aside from surgically based cases, the full complement of the CCS is infrequently clinically encountered. The patient described has a classic CCS from natural causes. This case report is unique in exhibiting a complete CCS with AHS secondary to an ischemic event affecting the left pericallosal region. To our knowledge this is the first case report of such a combination.

A 64 yr old right-handed mechanic presented with four weeks history of clumsy right hand with ongoing problems at work. He described stiffness and problems with co-ordination. At the time of presentation he was noted to be walking with his right arm behind him and not being aware of this. His initial examination showed Mini Mental Score of 26/30, with ongoing involuntary movements of his right arm (Video).Video shows spontaneous elevation of right arm with occasional myoclonic jerks. Video also demonstrates patient's difficulty in following simple motor tasks and his comments that his arm “has a mind of its own”.His MRI head (Figure 1) showed typical cortical ribboning pattern described in sporadic CJD and CSF Protein for 14-3-3, s100b and RT-QUIC findings were consistent with the diagnosis of CJD.Over next 4 weeks his cognitive function rapidly deteriorated with progressive worsening of his myoclonus. He died 4 weeks after his hospital discharge.There are three broad varieties of alien limb phenomenon (ALP) types described in the literature, frontal, callosal and sensory. Jerky (myoclonic) ALP is well described in patients with CJD, so CJD should be in the differentials in any patient presenting with sub-acute onset of ALP.

Callosal alien hand syndrome is characterized primarily by intermanual conflict and is associated with an anterior callosal lesion. We report a patient who presented with topographical disorientation and the callosal type alien hand sign. An MRI of the brain showed a right parietal lobe infarction. This is a rare example of callosal alien hand sign associated with a right parietal lesion. The right parietal lobe appeared to be responsible for the callosal hand sign in this patient, possibly due to interference with peristriate outflow pathways toward the parietal zones, where visual somatosensory interactions are likely to occur.

Background Infarcts of the corpus callosum are rare and have not been well documented previously. As for a variety of signs and symptoms presented, alien hand syndrome (AHS) can be easily overlooked. Case presentation In this report, we present a patient with a mixed types of AHS coexistence secondary to the corpus callosum infarction, including a motor type of AHS by intermanual conflict (callosal type AHS) and a sensory type of AHS by alien hand and left hemianesthesia (posterior AHS). Conclusions Our case may contribute to the early recognition of AHS and to explore the abnormal neural mechanism of AHS. To our knowledge, rare reports have ever documented such mixed AHS coexisting secondary to the callosal lesion, based on advanced neuroimaging methods as in our case.

Alien limb phenomenon is associated with different neurological disorders, such as stroke and corticobasal degeneration. It is usually caused by involvement of the corpus callosum, with or without the frontal regions. Rarely, it can result from insult in the posterior cerebral artery territory. Alien limb phenomenon is generally persistent. Here, an unusual case of transient alien hand phenomenon is reported.

In Stanley Kubrick's movie Dr Strangelove, the main character is described as "erratic" and displays a bizarre movement disorder. His right hand seems to be driven by a will of its own, at times clutching his own throat and at other times raising into a Nazi salute. Dr Strangelove must try to restrain this wayward limb with his left hand. Bizarre as this fictional character is, a similar movement disorder can occur in neurologic disease. The complex phenomenon associated with this disorder falls under the rubric of alien hand syndrome. This syndrome is characterized by a limb that seems to perform meaningful acts without being guided by the intention of the patient. Patients find themselves unable to stop the alien limb from reaching and grabbing objects, and they may be unable to release these grasped objects without using their other hand to pry open their fingers. These patients frequently express astonishment and frustration at the errant limb. They experience it as being controlled by an external agent and often refer to it in the third person. This article outlines the origins of the terminology used in describing this syndrome, early observations, and studies regarding its functional neuroanatomy.