What is it?
Locked-in syndrome (LIS) is a condition in which the patient is in a normal state of awareness but isn’t able to move or speak. This is because they suffer from a paralysis of nearly all voluntary muscles – often they can move their eyes, though. Coded messages through blinking or moving their eyes are practically the patient’s only way of communicating. Some patients also retain the ability to sense throughout their body. In a 2002 survey it was found that it took on average 3 months to recognize and diagnose LIS after the incident that caused it happened: it is very easy to mistake LIS for unconsciousness or even death.
Strokes are the most common cause of LIS, and while the exact prevalence rates are unknown it is thought that the syndrome affects under 1% of stroke sufferers. More than 85% of the affected are alive 10 years after onset.
What causes it?
The most common cause of LIS is a stroke. Other causes include poisoning and neurodegenerative diseases.
What happens during it?
Our brain is the source of our cognitive functions, and it also controls movement through sending signals down the spinal cord to the muscles to make them contract. In LIS, the upper parts of our brain responsible for things like consciousness stay intact, while the lower parts connecting our brain to our muscles are damaged. This most often happens because of a stroke. Blood flow to a certain brain area has been compromised because of, for example, a blood clot blocking the vessel, and the cells in that area soon begin to die because they can’t function for very long without oxygen. In LIS patients this has happened in the part of our brain that communicates the brain’s messages to the muscles. Even if the brain does send signals, they simply don’t get through anymore. The brain can and does recover from injuries to some extent, but in something as massive as a stroke, the effect is minor compared to the functions that have been lost. This is because neurons are highly specialized cells with very specific places and connections which makes regeneration a lot harden than for, say, skin cells. Injuries in the central nervous system often also result in the formation of scar tissue, and when the neurons try to form new connections across the site of injury, they can’t penetrate through it.
How can it be treated?
Unfortunately, any standard cure or treatment isn’t available. While it is very rare for patients to gain any control of movement, stimulating muscle reflexes electrically has been known to help some. The technology to help patients communicate is quite advanced, and things like electronic tracking of eye movement can be very helpful.
Sources: https://en.wikipedia.org/wiki/Locked-in_syndrome, http://cirrie.buffalo.edu/encyclopedia/en/article/303/#s2, en.wikipedia.org/wiki/Stroke, https://en.wikipedia.org/wiki/Neuroregeneration#Central_nervous_system_regeneration