Alien Hand Syndrome - Neurological Explanation and Medical Cause

Allison Pflanz -

A 77-year-old woman is watching TV feeling relaxed after a long day. Suddenly, she is startled by a hand stroking her hair and face. The catch? It was her hand. This woman is suffering from a disease with a name straight out of a science fiction novel: Alien Hand Syndrome (AHS). AHS is a neurological disorder in which a person experiences goal-oriented movement of the hand without conscious control. Alien Hand Syndrome is an extremely rare disorder, with only a few cases reported in scientific literature [1]. This is why the research, treatment, and even agreed upon definition and classification is not well established amongst the scientific community. 

What is Alien Hand Syndrome?

Alien Hand Syndrome was first described as a condition in which a person loses control of their hand, causing it to act independently. It refers to involuntary, complex, goal-directed activity of one limb. Goal-oriented activity refers to motions like brushing your hair, picking your ear, or touching your nose, as opposed to simpler movements like twitching [1]. One standout case of AHS follows Karen Byrne, a 55-year-old woman from New Jersey [2]. At the age of 27, her brain was cut in half through the corpus callosum, the structure of the brain that allows both hemispheres to communicate with each other. This procedure, called a corpus callosotomy, was used often in the mid-1900s to treat epilepsy. Karen appeared to be recovering well from the surgery until her doctors observed alarming behavior. “My hand started taking its clothes off,” Karen stated in an interview with NBC. All of a sudden, the hand seemed to “get angry” and was “tearing the buttons off the shirt” Karen was wearing. Karen and her doctors tried to stop the hand by yelling at it and eventually had to physically pin the hand down [2]. This was Karen’s first encounter with Alien Hand Syndrome.  

AHS was first described in 1908 by German neurologist Kurt Goldstein, who documented a patient presenting with symptoms similar to what is now classified under the syndrome [3]. Since Goldstein’s initial description, the medical community has proposed several definitions of AHS, but the most agreed upon is the feeling of foreignness in the limb, in addition to unintended movements of said limb. Three of the biggest determining factors in differentiating AHS from other diseases are the limb’s autonomous and involuntary movements, complexity of action, and the complaint of the limb feeling foreign [4]. Patients often express a fear of their own arm, equating it to something outside of their own self. For these reasons, many with AHS experience symptoms of other common mental illnesses. 

Associated Symptoms

AHS manifests in numerous different ways: from levitating of the alien limb, fighting against the body, or even grasping things without conscious direction, each patient presents a compelling story to be uncovered. As a patient living with AHS, Karen often describes her experience and symptoms as being ‘confusing’ and as if she was fighting her own body [2]. Karen described how she would light a cigarette, balance it on an ashtray, and then her left hand would reach forward and stub it out. Her hand would take things out of her handbag and she wouldn't realize so she would walk away. “I lost a lot of things before I realized what was going on." Karen’s experiences are textbook examples of some of the most common symptoms in AHS. 

Despite the simple premise, the actual symptoms of AHS are constantly growing and uniquely intertwined. The symptoms Karen was experiencing are termed self-oppositional behavior, sometimes also known as intermanual conflict [1]. Self-oppositional behavior is when the functional limb will do a task which the alien limb will automatically undo or will attempt to interfere as the action is occurring. For example, the unaffected limb could be trying to put on a jacket whilst the affected hand might be trying to take it off at the same time, or the patient will lose control of their hand as it grabs onto something and have to use their other hand to force the alien hand to let go. Karen Byrne predominantly presented with self-oppositional behavior. For example, “when [she] go[es] to light a cigarette, the hand will either put the cigarette out or flick the ashes around” [2].

Another fairly common symptom of AHS is groping/self-groping behavior where the alien hand will hold onto the patient's own body, often by pulling hair or hitting the patient. This can lead to similar responses as the self-oppositional movements, where the patient forcibly grabs the alien hand with their consciously functioning hand in an attempt to make the alien limb stop its behavior [5]. Karen Byrne exhibited groping behavior when her alien hand would grab her handbag and place it somewhere else without her conscious knowledge [2]. Another common symptom, alien hand sign, is the origin for where the ‘alien’ part of alien hand syndrome comes from. Alien hand sign is a subjective feeling that the hand is not one’s own, becoming the common face of alien hand syndrome [1].

Less common symptoms in AHS are supernumerary hand and levitating hand. Patients report symptoms of supernumerary hand and levitating hand less often by themselves, but rather in conjunction with the two most common symptoms. Supernumerary hand is a feeling of possessing an extra limb, aligning with how patients feel like the hand is not their own [1]. The symptom is more of a sensation and underlies most other symptoms of AHS, thus making it an important marker for AHS diagnoses. On the other hand, levitating hand is when the alien limb will stay hanging in the air without particular purpose or direction. This can occur anywhere between a few seconds to a few hours, leaving the patient constrained mobily. Although progress has been made in identifying symptoms, it is hard to classify the broad symptomatic manifestations of the disease under the current typology of AHS. 

AHS Typology

Alien Hand Syndrome can be classified into two overarching categories: frontal/parietal and callosal [6]. Researchers have found that AHS is a disease of the brain, but understanding how and why exactly Alien Hand Syndrome emerges in different patients is much trickier. 

Frontal Type

One notable patient with AHS following stroke is a 61-year-old patient who was diagnosed with the frontal-type AHS. After his stroke, an MRI revealed damage to his left frontal and parietal lobes. His main symptom was grabbing something and being unable to release it, a symptom typical of frontal-type AHS [6]. Frontal-type AHS often results from damage to the prefrontal cortex and/or parietal cortex and involves the frontal and parietal lobe, which are responsible for movement planning and high-level processes [5]. When the frontal and/or parietal lobes are damaged as a cause of AHS, it will often manifest as a disruption in communication between the two hemispheres. This results in one hand being voluntarily controlled while the other is involuntary [6]. Other areas affected are typically the supplementary motor area, important for initiation of movement, and the anterior cingulate cortex, important for attention and conscious awareness [5]. 

Lesions causing AHS typically occur in the corpus callosum, posterior parietal cortex, or certain frontal lobe regions (the supplementary motor area and anterior cingulate cortex) [1]. The posterior parietal cortex controls planned movements, so damage to it impairs the ability to execute them. This is why patients with AHS are often unaware of movements made by the alien limb. These lesions in the parietal cortex lead to increased activity in the frontal lobe’s primary motor area as opposed to less activation of the prefrontal cortex, which is in charge of intentional direction of the limb. This results in the disconnection between the movement of the limb and the absence of intentional movement [7]. In the frontal lobe, the motor areas are in charge of movement planning in limbs on opposite sides of each other. For example, the left motor area corresponds with the right side of the body and so forth. Thus, damage here can manifest in the typical symptom of involuntary movement, as well as intermanual conflict, where one limb goes against the actions of the other [7]. 

Callosal Type

Callosal-type AHS affects the corpus callosum, which is the bridge between the two sides of our brain responsible for allowing us to control our movements. Damage to this area, either by a stroke or other events, typically results in symptoms of self-oppositional behavior/intermanual conflict. When damaged, this can lead to unawareness of the action their alien limb is doing [6]. The loss of connection indicates the process is missing out on information from the motor center in the left hemisphere, a possible factor in AHS symptoms [5]. Interestingly, when the AHS type is callosal, the non-dominant hand often is the ‘alien limb’ for the patient, whereas in the frontal type, the ‘alien limb’ is the dominant hand [5]. Furthermore, all patients in reported cases of AHS literature have been right hand dominant or ambidextrous.  

Comparison of Types

Generally, patients with AHS have had damage to specific tissues in the brain, usually caused by strokes in the corpus callosum [1]. Strokes in this area break the hemispheres' connection and the ability for the two to communicate and plan coordinated actions. In extremely rare cases, AHS can manifest from a cardioembolic stroke, in which the heart pumps debris into the brain [1]. In addition to lesions caused by strokes, AHS has been reported after surgery on the corpus callosum, brain tumors, aneurysms, and degenerative diseases of the brain [1]. Diagnosis and treatment of the callosal type of AHS is much harder due to its rarity and nonspecific and hidden symptoms behind other brain injuries [6]. For people with AHS, preferential activation, which is when specific neurons are activated, has been observable after research and testing in the primary motor cortex during action of the alien limb. This isolated neural activity suggests isolation from the planning areas of the brain, hence why the alien limb presents as involuntary movement [7]. 

Diagnosing and distinguishing a patient’s symptoms as one type or the other proves to be difficult. For example, many times frontal AHS affects multiple other parts of the brain outside of the frontal and parietal region, presenting with symptoms similar to callosal AHS. Both of these types are highly generalized, as a lack of proper patient research and diagnoses makes it difficult to gain insight on the unique ways that AHS presents in each patient.

AHS in Perspective

As a movement disorder, AHS is often seen in context with other motion impairing diseases, most commonly Parkinson’s disease. Parkinson’s occurs when the dopamine-producing center of the brain deteriorates. This causes symptoms associated with low dopamine levels such as tremors and motion impairments. Most commonly, Parkinson's affects the ability to move in daily life, and even walk in progressed cases. In fact, AHS is even included as a common symptom of Parkinson-Plus syndrome, a group of multiple movement disorders associated with Parkinsons [8].

In these motor impairing conditions, AHS can present itself during the progression of the disorders, especially in corticobasal degeneration, a progressive brain disorder that causes nerve cells to shrink and eventually die [9]. Degeneration of specifically the frontal lobe, which is in charge of executive functioning and movement direction, can result in AHS and many patient cases presenting with this corticobasal syndrome will often also present with AHS [8]. Patients with corticobasal degeneration often have alien hand syndrome as well as apraxia, which is voluntary but impaired movement. While it is a syndrome by itself, AHS is commonly seen in combination with other movement disorders of the brain. 

Treatment and Diagnosis

At the time of writing, AHS has no single, fix-all treatment. Most patients who have this are treated for their symptoms, prescribed drugs to limit sporadic movements, or told to attempt to wait out the length of the symptoms, despite studies indicating that AHS does not usually deteriorate quickly over time. motor capabilities of a patient [5].motor capabilities of a patient [5].

For the 61-year-old AHS patient mentioned before, it was possible for rehabilitation to conquer some symptoms and provide a noticeable increase in control over certain movements in the alien limb [5]. His initial symptom was his non-dominant hand grabbing objects and not being able to release them, but prior to this research, there was no rehabilitation method that would help him regain some form of a normal lifestyle. The researchers and physical therapists worked on rehabilitation through speech therapy, neurocognitive training, and bimanual tasks (engaging both affected and unaffected limbs). One example was diverting attention to the side using black and white images and having the alien hand catch a cube. After twelve weeks of therapy, the patient had increased by 43 points on the Functional Index Measure (FIM), which measures the motor capabilities of a patient [5].

Generally during rehabilitation, if used at all, the patient and doctors will focus on the symptoms specific to the patient and developing exercises to test and retrain different motor control skills. Researchers found that encouraging patients to verbalize motor goals and visualize themselves performing the task increases their chance of progression in rehabilitation [5]. While there are some drugs, such as clonazepam, available that can produce resolution in symptoms, notably with levitating hands, the negative side effects often outweigh any positives. Clonazepam, known for its usage in treating epilepsy and other involuntary movements, works by increasing the amount of inhibitory neurotransmitters to help prevent more of these involuntary movements [10]. One study involving a 13-year-old girl who was treated with clonazepam and botox showed a 73% decrease in levitations and graspings by the alien limb [11]. However, these treatments were unable to restore conscious direction of the limb. Further, the treatment has numerous other side effects that bring into question the true effectiveness of the drug as in this study, researchers used botox to try to numb the arm completely, effectively stopping the involuntary movements but failing to address the underlying brain inactivity. Despite researched options for controlling symptoms, there are no approved or recommended drug treatments for AHS.

Depending on the cause of AHS, symptoms can go away after time. For example, if a patient’s AHS was onset by a stroke, it is highly possible that over time, the symptoms of AHS will fade with rehabilitation. However, for AHS associated with neurodegenerative diseases, symptoms are not expected to fade with time.

Diagnosing patients with AHS is a difficult process because it is very important to distinguish patients with AHS from patients who are suffering from a mental illness that causes symptoms similar to AHS [6]. For example, apotemnophilia is a disorder in which a patient has a strong desire to cut off their own limb and typically presents in similar ‘goal-directed’ movements as in AHS but is missing the sensation of limb alienation. AHS can also be misdiagnosed with somatic paraphrenia, where the patient will deny possession of one of their limbs, similarly to how AHS patients will feel as though their limb is not their own. It can also be misdiagnosed with a group of disorders known as body schema disorders, where the patient will have difficulty having a sense for the movement of their limb and understanding its body position [6]. This common confusion in diagnosis of disorders can result in patients enduring long and convoluted processes to obtain a diagnosis. 

Future Research and Implications

Due to the rarity of the syndrome, there is a large lack in research and patient studies on this disease, resulting in few case studies for doctors and affected patients to go off of. 

Some experiments have used Transcranial Magnetic Stimulation (TMS) to study AHS [3]. TMS involves using a magnetic coil and field to inactivate or activate specific parts of the brain region. By using observations from TMS data, researchers can draw associations between levels of brain activity and specific AHS symptoms. In the case study, researchers analyzed two cases of AHS resulting from an infarct, which is a dead tissue in the brain due to a lack of blood flow. After observing these patients, neurophysiological tests measured reduced muscle activity resulting from activating motor areas of the brain with TMS. It also showed no brain mediation of selective muscle activation, and no abnormalities in the electrical activity of the brain following touch. This indicates that the infarct has impacted how the muscles of the hand work in tandem, leading to irregularities in their movement patterns [3].

In a different case study observing patients who displayed AHS, patients were constantly monitored for vitals and symptoms progression [12]. The onset of AHS was observed and when the syndrome started in one hand, it progressed to affect many different limbs in six out of seven patients. Decreases in symptoms over time occurred in 68% of patients, while 32% saw a persistence [12]. 

When more research is conducted on the different patients and especially the neurophysiological basis for the syndrome, there is a potential for deeper understanding of related diseases such as Parkinson’s Disease.

Conclusion

For the 77-year-old woman, she had only a short period of time affected by AHS and was quickly treated for stroke. After diagnosis, her specific presentation of AHS could be connected to her stroke. However, for many patients suffering with AHS, their lives are put on hold by this disease and they lack definitive research conclusions and potent methods of treatment. They can wait months, even years to simply receive a diagnosis and effective treatment, putting their lives in limbo. In order to help this population, more research into this disease from a neurological perspective is needed to completely understand and hopefully treat it. 

Discoveries in AHS can mean leaps in how we view Parkinson’s and other motor related disorders. As research continues to be done in AHS, patients with all types of neurological diseases will be impacted positively as deeper understanding of the neural connections of movement disorders may improve rehabilitation methods. Although the neurological complexities of AHS prove it to be difficult to develop effective treatments, its impact on individual lives make it an important focus for the scientific community. 

References

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