Locked-in syndrome

Locked-in syndrome
Locked-in syndrome can be caused by stroke at the level of the basilar artery denying blood to the pons, among other causes.
Classification and external resources
Specialty Neurology
ICD-10 G93.8
ICD-9-CM 344.81
MeSH D011782

Locked-in syndrome (LIS) is a condition in which a patient is aware but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for vertical eye movements and blinking. The individual is conscious and sufficiently intact cognitively to be able to communicate with eye movements.[1] Total locked-in syndrome is a version of locked-in syndrome wherein the eyes are paralyzed as well.[2] Fred Plum and Jerome Posner coined the term for this disorder in 1966.[3][4] Locked-in syndrome is also known as cerebromedullospinal disconnection,[5] de-efferented state, pseudocoma,[6] and ventral pontine syndrome.


Locked-in syndrome usually results in quadriplegia and the inability to speak in otherwise cognitively intact individuals. Those with locked-in syndrome may be able to communicate with others through coded messages by blinking or moving their eyes, which are often not affected by the paralysis. The symptoms are similar to those of sleep paralysis. Patients who have locked-in syndrome are conscious and aware, with no loss of cognitive function. They can sometimes retain proprioception and sensation throughout their bodies. Some patients may have the ability to move certain facial muscles, and most often some or all of the extraocular muscles. Individuals with the syndrome lack coordination between breathing and voice.[7] This prevents them producing voluntary sounds, though the vocal cords are not paralysed.[7]


In children, the most common cause is a stroke of the ventral pons.[8]

Unlike persistent vegetative state, in which the upper portions of the brain are damaged and the lower portions are spared, locked-in syndrome is caused by damage to specific portions of the lower brain and brainstem, with no damage to the upper brain.

Possible causes of locked-in syndrome include:

Curare poisoning mimics a total locked-in syndrome by causing paralysis of all voluntarily controlled skeletal muscles.[9] The respiratory muscles are also paralyzed, but the victim can be kept alive by artificial respiration, such as mouth-to-mouth resuscitation. In a study of 29 army volunteers who were paralyzed with curare, artificial respiration managed to keep an oxygen saturation of always above 85%,[10] a level at which there is no evidence of altered state of consciousness.[11] Spontaneous breathing is resumed after the end of the duration of action of curare, which is generally between 30 minutes[12] and eight hours,[13] depending on the variant of the toxin and dosage.


Locked-in syndrome can be difficult to diagnose. In a 2002 survey of 44 LIS patients, it took almost 3 months to recognize and diagnose LIS after the patient had suffered the incident (i.e., a stroke or an injury) that had caused his/her LIS.[14] Locked-in syndrome may mimic loss of consciousness in patients, or, in the case that respiratory control is lost, may even resemble death. Patients are also unable to actuate standard motor responses such as withdrawal from pain; as a result, testing often requires making requests of the patient such as blinking or vertical eye movement.

Brain imaging may provide additional indicators of locked-in syndrome, as brain imaging provides clues as to whether or not brain function has been lost. Additionally, an EEG can allow the observation of sleep-wake patterns indicating that the patient is not unconscious but simply unable to move.[15]


Neither a standard treatment nor a cure is available. Stimulation of muscle reflexes with electrodes (NMES) has been known to help patients regain some muscle function. Other courses of treatment are often symptomatic.[16] Assistive computer interface technologies, such as Dasher, or OptiKey, combined with eye tracking, may be used to help patients communicate.


It is extremely rare for any significant motor function to return. The majority of locked-in syndrome patients do not regain motor control, but devices are available to help patients communicate. However, some people with the condition continue to live much longer,[17][18] while in exceptional cases, like that of Kerry Pink[19] and Kate Allatt,[20] a full spontaneous recovery may be achieved.


New direct brain interface mechanisms may provide future remedies; one effort in 2002 allowed a fully locked-in patient to answer yes-or-no questions.[21][22] In 2006, researchers created and successfully tested a neural interface which allowed someone with locked-in syndrome to operate a web browser.[23] Some scientists have reported that they have developed a technique that allows locked-in patients to communicate via sniffing.[24]

See also

Other similar conditions


  1. Duffy, Joseph. motor speech disorders substrates, differential diagnosis, and management. Elsevier. p. 295.
  2. Bauer, G.; Gerstenbrand, F. & Rumpl, E. (1979). "Varieties of the locked-in syndrome". Journal of Neurology. 221 (2): 77–91. doi:10.1007/BF00313105. PMID 92545.
  3. Agranoff, Adam B. "Stroke Motor Impairment". eMedicine. Retrieved 2007-11-29.
  4. Plum, F; Posner, JB (1966), The diagnosis of stupor and coma, Philadelphia, PA, USA: FA Davis, 197 pp.
  5. Nordgren RE, Markesbery WR, Fukuda K, Reeves AG (1971). "Seven cases of cerebromedullospinal disconnection: the "locked-in" syndrome". Neurology. 21 (11): 1140–8. doi:10.1212/wnl.21.11.1140. PMID 5166219.
  6. Flügel KA, Fuchs HH, Druschky KF (1977). "The "locked-in" syndrome: pseudocoma in thrombosis of the basilar artery (author's trans.)". Dtsch. Med. Wochenschr. (in German). 102 (13): 465–70. doi:10.1055/s-0028-1104912. PMID 844425.
  7. 1 2 Fager, Susan; Beukelman, Dave; Karantounis, Renee; Jakobs, Tom (2006). "Use of safe-laser access technology to increase head movements in persons with severe motor impairments: a series of case reports". Augmentative and Alternative Communication. 22 (3): 222–29. doi:10.1080/07434610600650318. PMID 17114165.
  8. Bruno MA, Schnakers C, Damas F, et al. (October 2009). "Locked-in syndrome in children: report of five cases and review of the literature". Pediatr. Neurol. 41 (4): 237–46. doi:10.1016/j.pediatrneurol.2009.05.001. PMID 19748042.
  9. Page 357 in: Damasio, Antonio R. (1999). The feeling of what happens: body and emotion in the making of consciousness. San Diego: Harcourt Brace. ISBN 0-15-601075-5.
  10. Page 520 in: Paradis, Norman A. (2007). Cardiac arrest: the science and practice of resuscitation medicine. Cambridge, UK: Cambridge University Press. ISBN 0-521-84700-1.
  11. Oxymoron: Our Love-Hate Relationship with Oxygen, By Mike McEvoy at Albany Medical College, New York. 10/12/2010
  12. For therapeutic dose of tubocurarine by shorter limit as given at page 151 in: Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. OCLC 51622037.
  13. For 20-fold paralytic dose of toxiferine ("calebas curare"), according to: Page 330 in: The Alkaloids: v. 1: A Review of Chemical Literature (Specialist Periodical Reports). Cambridge, Eng: Royal Society of Chemistry. 1971. ISBN 0-85186-257-8.
  14. León-Carrión, J.; van Eeckhout, P.; Domínguez-Morales Mdel, R.; Pérez-Santamaría, F. J. (2002). "The locked-in syndrome: a syndrome looking for a therapy". Brain Inj. 16 (7): 571–82. doi:10.1080/02699050110119781.
  15. Maiese, Kenneth (March 2014). "Locked-in Syndrome".
  16. lockedinsyndrome at NINDS
  17. Joshua Foer (October 2, 2008). "The Unspeakable Odyssey of the Motionless Boy". Esquire.
  18. Piotr Kniecicki "An art of graceful dying". Clitheroe: Łukasz Świderski, 2014, s. 73. ISBN 978-0-9928486-0-6
  19. Stephen Nolan (August 16, 2010). "I recovered from locked-in syndrome". BBC Radio 5 Live.
  20. "Woman's recovery from 'locked-in' syndrome". BBC News. March 14, 2012.
  21. Parker, I., "Reading Minds," The New Yorker, January 20, 2003, 52–63
  22. Keiper, Adam (Winter 2006). "The Age of Neuroelectronics". The New Atlantis. pp. 4–41.
  23. Karim AA, Hinterberger T, Richter J, Mellinger J, Neumann N, Flor H, Kübler A, Birbaumer N. "Neural internet: Web surfing with brain potentials for the completely paralyzed". Neurorehabilitation & Neural Repair. 40 (4): 508–515.
  24. "'Locked-In' Patients Can Follow Their Noses". Science Mag. 26 Jul 2010. Retrieved 27 Jul 2010.

Further reading

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