A Mind of Its Own
Imagine waking up in the middle of the night to find yourself being choked - by your own hand. For some individuals, this is a reality. This situation arises from a condition called Alien Hand Syndrome (AHS).1 Alien Hand Syndrome is a neurological condition in which individuals’ limbs move without being under voluntary control; as if their limbs have a mind of their own.1,2 AHS acts as an umbrella term for various conditions in which a limb is out-of-control, and the left hand is most commonly affected. Individuals often reach for objects and manipulate them as well, leading the usually in-control hand restraining the out-of-control limb. Individuals with AHS may feel completely normal sensations in the out-of-control limbs, but believe the hand behaves in an alien manner in comparison to the rest of the body. Many claim the occurrence of AHS is the result of a disconnect between thought and action. As such, individuals with AHS feel a loss of agency; they are effectively losing their subjective awareness including their control of voluntary actions, while still maintaining ‘ownership’ of their limbs. AHS currently has no treatment, but scientists are working hard to create any treatment in order to reduce symptoms.1,2
Alien Hand Syndrome is a neurological disease. Neurological disorders are diseases which affect the nervous system, which includes the brain, spinal cord, and nerves.3 Neurological disorders can have a wide range of causes including bacterial, viral, fungal, and parasitic.3 For example, infection by the Plasmodium parasites cause malaria which often leads to spinal cord disorders (Figure 1), and infection by the bacterium Mycobacterium tuberculosis in the central nervous system can lead to irreparable damage such as immunosuppressive activity.4,5 Common neurological disorders include epilepsy, in which the individual constantly experiences seizures; Alzheimer's disease, in which individuals undergo mental deterioration and suffer from memory loss; and cerebrovascular diseases such as strokes, migraines, and much more.6,7 Less common neurological disorders include multiple sclerosis which is an autoimmune disease affecting the myelin covering nerves, Parkinson’s disease, and brain tumours and much more.3 Neurological disorders are relatively common worldwide, with hundreds of millions of individuals affected. However, AHS remains a rare disorder under the vast umbrella described above.3
Although there are various subtypes of AHS, three major types dominate: corpus callosum damage, frontal lobe damage, and parietal and occipital lobe damage.1 The corpus callosum integrates motor, sensory, and cognitive function in one hemisphere of the brain with the other hemisphere.8 If the corpus callosum is damaged, purposeful actions can arise in the individual’s non-dominant hand.1,8 Some individuals with damage to their corpus callosum may also suffer from ‘the callosal variant’ in which the individual’s affected hand will oppose voluntary actions performed by the normal-functioning hand. Agonistic and diagnostic dyspraxia are often associated with these patients. Agonistic dyspraxia is when an individual is asked to perform movements with one hand, but the other hand compulsively performs the movement instead. Alternatively, diagnostic dyspraxia occurs when there is a conflict between the action which is being performed by the ‘normal-functioning’ hand and the interfering action of the ‘abnormal’ hand. If an individual has unilateral damage to the frontal lobe, grasping, reaching, and other such movements can be involuntarily triggered within the contralateral hand. If parietal or occipital lobe damage occurs, AHS manifests in a distinct ‘posterior variant.’ In this situation, movements tend to appear opposite to the majority of other AHS symptoms. Instead of reaching out and grasping objects, which is known as the “frontal variant,” the palmar surface of the affected hand withdraws from the surface.1
As AHS encompasses various motor control disorders, there is no one cause.1 However, there is a common emerging factor: the area of the brain which controls hand movement, the premotor cortex, is unaffected by the influences of the area of the brain which regulates muscle movement, the premotor cortex.9 (Figure 2). Two major theories of causation exist which are disconnection, and loss of inhibitions.1,9 The theory of Disconnection suggests that AHS results when different parts of the brain are engaged in different motor movements, causing a disconnect to occur. As such, the individual is unable to generate a conscious feeling of self-control over the movements. Once again, the “sense of agency” is lost.1,9 Loss of inhibition theorizes that the brain has “premotor” or “agency” systems which are in charge of processing the transformation of intentions into actions. Damage to this system may, in turn, lead to the development of AHS. Along with these two theories, AHS may develop as a serious side effect of brain surgeries, with the majority of surgery-related cases occurring due to the accidental severing of the corpus callosum.1,9
Alien Hand Syndrome is as terrifying as it is unpredictable. This was observed in the case of a 77-year old woman, published in Baylor University Medical Center Proceedings in 2014.2 The patient complained of “observing her left hand moving without her knowledge while watching television.” At times, her left hand would stroke her face and hair as if another entity was controlling it. Movements such as these would last around half an hour. Unfortunately, after recovery, the patient developed left hemiparesis, in which the entire left side of her body was weakened. After an investigation, her case of AHS was revealed to be due to a stroke which affected both her left and right parietal lobes. Cases like the above help highlight the unpredictable nature of the disorder. Although extremely uncommon, even common conditions such as strokes can lead to the development of the rare disease.1,2
Although there is currently no cure, scientists and physical therapists have worked together over recent years to formulate non-invasive methods to reduce symptoms such as learning task therapies.1 For example, one therapy aims to force the brain of the affected individual to keep the nonfunctional hand occupied in order to allow the other hand to carry on with tasks. In some cases, the nonfunctional hand may be able to re-learn some specific learned tasks which in turn restores voluntary control, as a result of this therapy. With repeated practice, this therapy is quite effective, and it is possible to partake in regular day-to-day activities in affected individuals. Many such behavioural therapies exist to try and control the nonfunctional hand. Other therapies used for various symptoms within the umbrella of AHS include trapping the nonfunctional hand between the individual’s legs, slapping the nonfunctional hand, as well as application of warm water.1
AHS has come up widely in popular culture in recent years due to its fascinating presentation. Stories about patients with AHS have appeared in popular TV shows such as House. Furthermore, a Discovery Channel documentary called Dark Matters: Twisted But True described the disorder’s origin and history.10,11 This rare disease leads to difficulties in individuals’ lives, often disrupting their everyday behaviours and causing issues such as being unable to brush their teeth, cook or clean, and other such routine tasks. Research continues to evolve regarding AHS and other rare neurological conditions. Research such as this allows individuals who suffer from the condition to lead as normal lives as possible.
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2. Panikkath R, Panikkath D, Mojumder D, Nugent K. The alien hand syndrome. Proc (Bayl Univ Med Cent). 2014;27(3):219-220.
3. What are neurological disorders?. World Health Organization. 2017. Available at: http://www.who.int/features/qa/55/en/.
4. Osuntokun B. Malaria and the nervous system. Afr J Med Med Sci. 1983;12(3-4):165-72.
5. Rock R, Olin M, Baker C, Molitor T, Peterson P. Central Nervous System Tuberculosis: Pathogenesis and Clinical Aspects. Clinical Microbiology Reviews. 2008;21(2):243-261. doi:10.1128/cmr.00042-07.
6. Epilepsy. University of Maryland Medical Center. 2017. Available at: http://umm.edu/health/medical/reports/articles/epilepsy.
7. Alzheimer disease. University of Maryland Medical Center. 2017. Available at: http://umm.edu/health/medical/altmed/condition/alzheimers-disease.
8. Atlas: Corpus Callosum. Central Nervous System - Visual Perspectives. Cnsvpstanfordedu. 2017. Available at: http://cnsvp.stanford.edu/atlas/corpus_callosum.html.
9. Goldberg G., Bloom K. The Alien Hand Sign. American Journal of Physical Medicine & Rehabilitation. 1990;69(5):228-238. doi:10.1097/00002060-199010000-00002.
10. "House M.D." Both Sides Now (2009) - Synopsis. IMDb. 2017. Available at: http://www.imdb.com/title/tt1413129/synopsis.
11. D'Innella A, Noble J, Hosler J et al. "Dark Matters: Twisted But True" It's Alive!/Tripping with Uncle Sam/My Hand Is Killing Me (TV Episode 2011). IMDb. 2017. Available at: http://www.imdb.com/title/tt2765476/.
Cite This Article:
Misra A., Zheng K., Chan G., Ho J. A Mind of Its Own. Illustrated by H. Zhang. Rare Disease Review. June 2017. DOI:10.13140/RG.2.2.21983.05288.