What is Locked-In Syndrome? - Definition & Causes

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson is going to discuss a condition known as locked-in syndrome. You'll also learn about its numerous causes, including some major ones and even some reversible ones.

Deciding to Live or to Die

While a bit morbid to think about, most individuals have the relative freedom and important ability to make their own choices regarding their medical treatment. But imagine if you did not have this ability. You could not decide on your own course of treatment at all; it was up to someone else to make that decision for you, and you would be unable to even communicate your desires. Does that sound terrible?

Unfortunately, this scenario is something people with locked-in syndrome face. Let's define this condition and go over its causes in this lesson.

Locked-In Syndrome

Locked-in syndrome (LIS), sometimes called a pseudocoma, is a condition where a person has a virtually complete or complete inability to move any part of their body yet they are fully conscious and aware of their surroundings. This means, by extension, they are unable to speak nor communicate the fact that they are conscious even if others, such as physicians, think they are in a coma. By even further extension, this means life or death decisions can be made for the 'comatose' patient, of which they are aware of, but can do nothing about.

This condition was described by none other than Alexandre Dumas, the author of The Three Musketeers and The Count of Monte Cristo. In the latter book, there is a character, Monsieur Noirtier de Villefort, who is described, in short, as a living corpse. Interestingly, Dumas described LIS decades before the medical community ever did!



The most common cause of LIS is some sort of damage to the underside of the pons, a structure that is part of the brainstem. The brainstem is the part of our brain that is responsible for controlling many of our most important functions, like breathing. In a few cases, LIS can be caused by damage to the midbrain, another part of the brainstem.

The damage sustained during LIS is most commonly vascular in its origin and pathology. In other words, the damage stems from a blood-vessel related problem. The two broad causes of this are a burst blood vessel or a blocked blood vessel, as per a brainstem stroke. In either case, the brainstem doesn't get enough oxygenated blood and nutrition, resulting in damage to its nerve cells.


Other causes of LIS include:

  • Traumatic brain injury, which may end up compressing the brainstem and damaging it that way.
  • A brainstem tumor or abscess that can either compress or directly invade and destroy the brainstem's tissues.
  • The very last stage of ALS, amyotrophic lateral sclerosis (Lou Gehrig's disease), a condition where nerve cells die.
  • Infection, as per encephalitis.
  • Drug toxicity or a vaccine reaction.
  • Long-term hypoglycemia, or low blood sugar.
  • Severe cases of peripheral polyneuropathy. This is where nerves that allow a person to move are damaged.


Temporary and reversible LIS-like states can also occur. These may occur as a result of a few disease processes, such as nerve damage sustained as a result of infectious processes.

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