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Locked-in syndrome

Locked-in syndrome
CerebellumArteries.svg
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
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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.Total locked-in syndrome, or completely locked-in state (CLIS), is a version of locked-in syndrome wherein the eyes are paralyzed as well.Fred Plum and Jerome Posner coined the term for this disorder in 1966. Locked-in syndrome is also known as cerebromedullospinal disconnection,de-efferented state, pseudocoma, 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. This prevents them producing voluntary sounds, though the vocal cords are not paralysed.

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. 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%, a level at which there is no evidence of altered state of consciousness. Spontaneous breathing is resumed after the end of the duration of action of curare, which is generally between 30 minutes and eight hours, depending on the variant of the toxin and dosage.


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