Cataplexy

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(from Greek, kata: down, plessein: strike) Cataplexy (adjective: cataplectic) is a cardinal symptom of NARCOLEPSY in which muscle tone is suddenly lost (ATONIA) as it is during REM SLEEP (rapid eye movement sleep) causing individuals to collapse. It often occurs in combination with a SLEEP ATTACK, though the two states are dissociable. When consciousness is not lost (that is, cataplexy without sleep attack) a distressing condition of waking immobility is produced.

Cataplexy is particularly associated with strong EMOTION—intense emotions can trigger an attack. Cataplexy is in effect the opposite of REM WITHOUT ATONIA: cataplexy is the inappropriate presence of atonia during the waking state. REM without atonia is the absence of atonia during REM sleep. The behaviour of animals which ‘play dead’ in order to avoid predators has also been described as cataplectic, though whether or not this is the same as the condition associated with narcolepsy is uncertain.

See also: sleep paralysis

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