Restless legs syndrome and periodic limb movement disorders.

Clinical confusion around restless legs syndrome (RLS), periodic limb movements during sleep (PLMS), and periodic limb movement disorder (PLMD) usually begins with a familiar sequence: the patient sleeps badly, the sleep study shows leg movements, and the report starts to sound like the diagnosis. The labels need more separation than that. RLS is diagnosed clinically from the history: an urge to move, often with uncomfortable sensations, brought out by rest, eased by movement, and worse in the evening or at night. PLMS are scored motor events. PLMD is reserved for the smaller group in whom those events plausibly account for sleep disturbance or daytime impairment after RLS, sleep-disordered breathing, narcolepsy, REM sleep behavior disorder, drug effects, and other neurological or medical causes have been considered. Biology is not a tidy dopamine story. Iron handling in the brain remains one of the more reproducible findings, although ferritin and transferrin saturation are only rough clinical proxies for central iron. Dopaminergic, adenosinergic, glutamatergic, spinal, autonomic, and genetic findings each explain part of the syndrome. Large genetic datasets, quantitative imaging, home movement recording, automated PLMS scoring, and autonomic measures have widened the field. Their immediate value is uneven: some help with mechanisms, some with measurement, and only a few currently change treatment decisions. Management still begins at the bedside. A typical RLS history, an incidental PLMS index, and possible PLMD lead to different choices. Iron indices should be checked early, medication and respiratory triggers need to be addressed, and dopamine agonist escalation should be avoided when augmentation is suspected. Current treatment is more cautious than older dopamine-centered practice: iron repletion when indicated, alpha-2-delta ligands for many chronic persistent cases, specialist use of opioids for severe refractory disease, and a selective role for device-based therapy. The chapter follows that clinical order rather than treating leg movement as a single target.