Sensorimotor disorder with an urge to move the legs at rest, relieved by movement, worse in the evening.
Also known as: RLS, Willis-Ekbom disease, restless leg syndrome
Overview
A sensorimotor disorder characterized by an irresistible urge to move the legs, usually accompanied by uncomfortable sensations, that begins or worsens at rest, is partially or fully relieved by movement, and is worse in the evening or at night (URGE mnemonic / IRLSSG essential criteria).
Epidemiology
Prevalence 5-10% in adults of European descent; lower in Asian populations. Female predominance ~2:1. Onset peaks before age 20 (primary, familial) and again in middle-late adulthood. ~40-60% report a positive family history.
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Question 1NeurologyMedium
A 54-year-old woman reports several months of an irresistible urge to move her legs that comes on each evening when she sits down to relax. She describes a deep, crawling, "creepy-crawly" sensation in her calves that improves when she walks around or stretches but returns once she lies still in bed. The symptoms delay sleep onset, and her husband notes that she repeatedly kicks her legs during the night. She takes no neuroleptics or antiemetics. Neurologic exam, including reflexes and sensation, is normal; serum ferritin is 18 ng/mL. Which of the following is the most likely diagnosis?
APeripheral neuropathy
BRestless legs syndrome
CAntipsychotic akathisia
DNocturnal leg cramps
Reveal answer & full explanation
Correct answer: B — Restless legs syndrome
APeripheral neuropathy
BRestless legs syndrome✓
CAntipsychotic akathisia
DNocturnal leg cramps
Why Restless legs syndrome is correct
The vignette meets all five IRLSSG essential criteria: an urge to move the legs with uncomfortable (crawling) sensations, onset at rest, relief with movement, an evening/night circadian pattern, and no alternative explanation.
Partner-witnessed nocturnal leg kicking reflects periodic limb movements of sleep, which commonly coexist with RLS.
A low serum ferritin (18 ng/mL) supports the diagnosis — brain iron deficiency is central to RLS pathophysiology, and ferritin should be checked and repleted toward >75-100 ng/mL even when hemoglobin is normal.
Why the others are wrong
Peripheral neuropathy produces constant stocking paresthesias with sensory loss and reduced reflexes; it is not relieved by movement and lacks the evening worsening seen here, and her exam is normal.
Antipsychotic akathisia is a generalized inner restlessness from dopamine antagonists (neuroleptics, antiemetics) or SSRIs that is not relieved by walking and lacks a circadian pattern; she takes no such medications.
Nocturnal leg cramps are sudden painful muscle contractions relieved by stretching the cramped muscle, without the persistent urge to move or the characteristic crawling sensation.
Question 2NeurologyMedium
A 52-year-old woman reports an irresistible urge to move her legs that comes on each evening when she settles into bed, accompanied by a crawling sensation that is relieved when she gets up and walks. Symptoms have worsened over the past year and now disrupt her sleep. Her husband notes she kicks her legs repeatedly during the night. She takes no medications. Neurologic exam, including reflexes and sensation, is normal. Which of the following is the most appropriate initial laboratory test?
AVitamin B12 and folate levels
BErythrocyte sedimentation rate
CSerum ferritin and iron panel
DSerum creatine kinase level
Reveal answer & full explanation
Correct answer: C — Serum ferritin and iron panel
AVitamin B12 and folate levels
BErythrocyte sedimentation rate
CSerum ferritin and iron panel✓
DSerum creatine kinase level
Why Serum ferritin and iron panel is correct
This vignette meets the IRLSSG essential criteria for restless legs syndrome (urge to move, worse at rest, relieved by movement, worse in the evening, partner-witnessed periodic limb movements).
RLS is best understood as a brain iron-deficiency state, so iron studies are the single most important workup test because low body iron stores are a treatable contributor.
Ferritin and transferrin saturation guide therapy, since iron repletion is indicated when ferritin is below 75-100 ng/mL even when hemoglobin is normal, so iron studies must be checked in every RLS patient.
Why the others are wrong
Vitamin B12 and folate levels are reasonable only when peripheral neuropathy or a macrocytic anemia is suspected; this patient has a normal neurologic exam and no sensory deficit, so they are not the initial test.
Erythrocyte sedimentation rate is a nonspecific inflammatory marker with no role in diagnosing or directing RLS therapy.
Serum creatine kinase level reflects muscle injury such as myopathy or rhabdomyolysis; RLS is a sensorimotor CNS disorder, not a primary muscle disease, so it does not discriminate.
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Best understood as a brain iron deficiency state with altered central dopaminergic, glutamatergic, and adenosine signaling. CSF ferritin is low even with normal serum ferritin in many patients. Genetic variants in MEIS1, BTBD9, and PTPRD confer risk. Periodic limb movements of sleep (PLMS) commonly coexist.
Anxiety with motor restlessness — Generalized restlessness, no temporal pattern, no relief with movement
Periodic limb movement disorder (PLMD) — Stereotyped movements during sleep without subjective urge; often coexists with RLS
Diagnostic workup
Diagnostic criteria
IRLSSG essential criteria (all 5): (1) urge to move legs, usually with uncomfortable sensations; (2) begins or worsens during rest/inactivity; (3) partially or totally relieved by movement; (4) worse in the evening or night; (5) not solely accounted for by another condition (cramps, positional discomfort, neuropathy).
Labs
Ferritin and transferrin saturation — the most important laboratory test; treat to ferritin >75-100 ng/mL
CBC, BMP, BUN/Cr (CKD evaluation)
TSH, fasting glucose/A1c, B12 if neuropathy suspected
Medication and substance review (SSRIs, antihistamines, dopamine antagonists, caffeine, alcohol)
Imaging
Routine imaging not indicated
Polysomnography reserved for diagnostic uncertainty or to evaluate PLMS / coexisting sleep apnea
Diagnostic algorithm
flowchart TD
A[Urge to move legs<br/>worse at rest/night,<br/>relieved by movement] --> B[Meet IRLSSG<br/>5 essential criteria]
B --> C[Check ferritin,<br/>review medications,<br/>screen for CKD/<br/>pregnancy/neuropathy]
C --> D{Ferritin<br/><75-100?}
D -->|Yes| E[Oral or IV iron]
D -->|No| F[Initial therapy:<br/>alpha-2-delta ligand<br/>(gabapentin enacarbil,<br/>pregabalin)]
F --> G{Refractory or<br/>severe?}
G -->|Yes| H[Dopamine agonist<br/>(low dose) OR<br/>low-dose opioid]
H --> I{Augmentation<br/>on DA?}
I -->|Yes| J[Reduce DA,<br/>switch to gabapentinoid<br/>or opioid]
G -->|No| K[Continue,<br/>optimize sleep,<br/>recheck ferritin]
Stepwise management of restless legs syndrome with augmentation pathway.
Treatment
First-line
Iron repletion if ferritin <75-100 ng/mL: oral iron (ferrous sulfate 325 mg with vitamin C every other day) OR IV iron (ferric carboxymaltose, iron sucrose) for severe or oral-intolerant cases
Alpha-2-delta calcium channel ligands — gabapentin enacarbil 600-1200 mg, pregabalin 150-450 mg, or gabapentin 300-1200 mg at bedtime; preferred over dopamine agonists due to lower augmentation risk
Dopamine agonists — pramipexole 0.125-0.5 mg, ropinirole 0.25-4 mg, rotigotine patch 1-3 mg/24 h — NO LONGER recommended as standard/first-line therapy (AASM 2024 conditionally recommends against routine use) because of augmentation and impulse-control disorder risk; reserve for selected cases at lowest effective dose
Sleep hygiene; reduce caffeine, alcohol, nicotine; identify and stop aggravating medications when possible
Augmentation management
Augmentation = paradoxical worsening of symptoms with chronic dopamine agonist use (earlier onset, spread to arms, increased intensity)
Avoid escalating dopamine agonist dose, which worsens augmentation
Severe/refractory RLS
Low-dose long-acting opioids (oxycodone CR, methadone, buprenorphine) — reserved for refractory disease with shared decision-making about risks
Combination of alpha-2-delta ligand + dopamine agonist or opioid
Address coexisting OSA
Pregnancy
Optimize iron stores; oral iron preferred
Non-pharmacologic measures (stretching, leg massage, warm baths, pneumatic compression)
Avoid dopamine agonists and gabapentinoids in first trimester when possible; clonazepam or low-dose opioid only if severely impairing sleep
Second-line / adjunct
Pneumatic compression devices
Yoga, exercise, mindfulness
Treat coexisting OSA — CPAP can improve RLS symptoms
Complications
Chronic insomnia and daytime fatigue
Depression and anxiety
Augmentation with chronic dopamine agonist therapy
Impulse control disorders (pathologic gambling, hypersexuality, binge eating) with dopamine agonists
Opioid use disorder if opioids required long-term
PANCE pearls
Check ferritin in every patient with RLS — target >75-100 ng/mL even if hemoglobin is normal.
Gabapentinoids are increasingly favored over dopamine agonists as first-line pharmacotherapy due to augmentation risk.
Augmentation differs from tolerance: symptoms appear earlier in the day, are more intense, and spread to new body parts.
Diphenhydramine, metoclopramide, and SSRIs are common iatrogenic triggers — review medications carefully.
Severe iron-deficient RLS responds dramatically to IV iron — consider in patients with persistent symptoms despite oral therapy.
References
AASM 2024 — Winkelman JW et al. Treatment of restless legs syndrome and periodic limb movement disorder: An AASM clinical practice guideline. J Clin Sleep Med 2024 (latest version).
IRLSSG — Allen RP et al. Restless legs syndrome/Willis-Ekbom disease diagnostic criteria: updated IRLSSG consensus criteria. Sleep Med 2014;15:860-873.
IRLSSG Iron Consensus — Allen RP et al. Evidence-based and consensus clinical practice guidelines for the iron treatment of RLS/WED. Sleep Med 2018;41:27-44.
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