Sleep-Related Movement Disorders
Restless legs syndrome
RLS is a clinical diagnosis requiring an urge to move the legs, worse at rest and in the evening, relieved by movement. It is associated with iron deficiency, pregnancy, and renal disease. Check ferritin; iron supplementation is considered when ferritin is low (often <75-100 ng/mL). Dopamine agonists and alpha-2-delta ligands (gabapentin, pregabalin) are treatments; augmentation is a risk with dopaminergic therapy.
Periodic limb movements
PLMS are repetitive limb movements during sleep, often accompanying RLS, and are scored on PSG. They can cause arousals and fragmented sleep but may be asymptomatic.
Traps
Do not confuse RLS with nocturnal leg cramps or neuropathy. RLS is worse at rest and in the evening, which distinguishes it. Augmentation (earlier onset, more intense symptoms) is a key complication of dopamine agonists. PLMS alone does not require treatment if asymptomatic.
Rule of thumb: In RLS, check ferritin and treat iron deficiency before escalating to dopamine agonists; watch for augmentation.