What does “locked-in syndrome” mean in the context of ALS?

“Locked-in” is an English term that can be translated as “being trapped.” The term “locked-in syndrome” (LIS) is used to describe a situation in which people have lost their ability to move but remain fully conscious.

In very advanced stages of ALS, locked-in syndrome may develop. The muscles of the limbs, trunk, tongue, and throat cannot be moved. The eye muscles are also affected, making it impossible to move the eyes, blink, or close the eyelids (complete LIS). When the body is immobile but communication is possible through preserved eye movements, the term “incomplete LIS” is used.

The development of LIS in ALS is very rare and affects people who have undergone life-prolonging measures (particularly mechanical ventilation). For the majority of ALS patients, the prospect of LIS is unacceptable. The onset of LIS is one of the main reasons for discontinuing ventilator therapy (and accompanying palliative care).