Sleep-Related Movement Disorders and Parasomnias
What you must know
Restless legs syndrome (RLS) is a clinical diagnosis: urge to move, worse at rest, relieved by movement, worse in evening/night. Check ferritin; treat iron deficiency (target ferritin >75-100 ng/mL). Dopamine agonists and alpha-2-delta ligands (gabapentin, pregabalin) are options; watch for augmentation with dopamine agonists.
Periodic limb movements of sleep (PLMS) are scored by the PLM index; PLMS alone does not require treatment unless associated with symptoms or arousals.
Parasomnias divide into NREM (confusional arousals, sleepwalking, sleep terrors-usually from N3, often amnestic) and REM (REM sleep behavior disorder [RBD], nightmares). RBD involves dream enactment with loss of REM atonia; it is strongly associated with synucleinopathies (Parkinson disease, Lewy body dementia, multiple system atrophy) and often precedes them by years.
Traps
- Treating PLMS without symptoms.
- Missing RBD because the patient recalls dreams-RBD patients often do recall dream content.
- Confusing sleep terrors (NREM, amnestic, child) with nightmares (REM, recalled).
- Forgetting to screen ferritin in RLS.
Rule of thumb
"NREM parasomnias: early night, amnestic; REM parasomnias: late night, recalled."
Worked example
A 68-year-old man punches and kicks during sleep and recalls being chased in dreams. This is RBD; confirm with PSG showing REM without atonia. Counsel on safety and consider melatonin or clonazepam; screen for neurodegenerative disease.