What is REM sleep without atonia (RSWA) and in which conditions is it seen?

What is REM sleep without atonia (RSWA) and in which conditions is it seen?

• A. Absent/abnormal muscle atonia during REM; seen in RBD and some neurodegenerative conditions.
• B. Increased muscle tone during REM sleep; seen in narcolepsy.
• C. Normal REM atonia; seen in healthy sleep.
• D. Absence of REM sleep entirely.

Answer: (A)

REM sleep without atonia is when the normal paralysis that accompanies dreaming during REM sleep does not occur or is incomplete, so muscles remain active or twitch. This happens because the brainstem circuits that enforce REM-atonia aren’t functioning properly. It’s a hallmark of REM Sleep Behavior Disorder, where people may act out dreams because they’re not paralyzed during REM. RSWA can also appear in several neurodegenerative diseases that affect these brainstem pathways, such as Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. This description is distinct from increased muscle tone during REM, which isn’t how RSWA is defined, and it’s not normal REM in healthy sleep, nor does it imply there is no REM sleep at all.

REM sleep without atonia is when the normal paralysis that accompanies dreaming during REM sleep does not occur or is incomplete, so muscles remain active or twitch. This happens because the brainstem circuits that enforce REM-atonia aren’t functioning properly. It’s a hallmark of REM Sleep Behavior Disorder, where people may act out dreams because they’re not paralyzed during REM. RSWA can also appear in several neurodegenerative diseases that affect these brainstem pathways, such as Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. This description is distinct from increased muscle tone during REM, which isn’t how RSWA is defined, and it’s not normal REM in healthy sleep, nor does it imply there is no REM sleep at all.