What is Restless Leg Syndrome?
Restless Legs Syndrome (RLS) is a neurological sensorimotor disease characterized by an irresistible urge to move the legs, typically accompanied by uncomfortable sensations that worsen during rest, improve with movement, and follow a circadian pattern with evening/nighttime predominance. 1
Core Definition and Classification
RLS profoundly disturbs sleep and quality of life, with variable expression influenced by genetic, environmental, and medical factors. 1 The condition is specifically classified as a neurological disorder affecting the nervous system, not merely a sleep disorder. 2
Essential Diagnostic Features (All Five Must Be Present)
The International Restless Legs Syndrome Study Group established five essential criteria that must all be met for diagnosis: 1
An urge to move the legs usually (but not always) accompanied by uncomfortable and unpleasant sensations in the legs—though sometimes the arms or other body parts may be involved. 1
Symptoms begin or worsen during rest or inactivity, such as lying down or sitting. 1
Movement provides relief—the urge and unpleasant sensations are partially or totally relieved by movement (walking, stretching) at least as long as the activity continues. 1
Circadian pattern—symptoms only occur or are significantly worse in the evening or night compared to daytime. 3
Exclusion of mimics—the symptoms cannot be solely accounted for by another medical or behavioral condition. 1
Clinical Significance and Impact
For RLS to be clinically significant, symptoms must cause substantial distress or impairment in social, occupational, educational, or other important functional areas through their impact on sleep, energy/vitality, daily activities, behavior, cognition, or mood. 1
Clinical Course Patterns
Chronic-persistent RLS: Symptoms occur on average at least twice weekly for the past year when untreated. 1
Intermittent RLS: Symptoms occur on average less than twice weekly for the past year, with at least 5 lifetime events. 1
Symptom Variability
Symptoms vary considerably in frequency (from less than once monthly to daily) and severity (from mildly annoying to disabling), and may remit for various periods. 1 The mean duration of RLS in clinical trials ranged from 16 to 22 years, with onset occurring at a mean age of approximately 54 years. 4
Critical Diagnostic Pitfall: RLS Mimics
Without proper differential diagnosis, 16% of patients who do not have RLS will be misclassified if only the first four symptom criteria are assessed. 1, 3 Common conditions that superficially meet the first four diagnostic criteria but are NOT RLS include: 1
- Leg cramps
- Leg edema
- Venous stasis
- Positional discomfort
- Muscle aches (myalgia)
- Habitual foot tapping
- Arthritis
Associated Features
Periodic leg movements: Patients with RLS often display periodic limb movements during sleep or resting wakefulness. 5
Sleep disturbance: RLS frequently causes severe sleep fragmentation and characteristic periodic limb movements during sleep identifiable on polysomnographic recording. 6
Quality of life impact: RLS may cause poor quality of life, depressive and anxious symptoms, and may be a risk factor for cardiovascular disease. 7
Primary vs. Secondary RLS
Primary (idiopathic) RLS develops at an earlier age with strong genetic basis and frequent familial history. 3
Secondary RLS typically presents later in life (fifth to seventh decade) without family history, and may occur due to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy, or certain medications including antipsychotics and antidepressants. 7, 3
Pathophysiological Mechanisms
The underlying pathophysiology involves reduced intracellular iron in the substantia nigra impairing dopamine transport in most patients. 3 Additional mechanisms under investigation include dysfunction in dopaminergic and nociceptive systems, altered adenosine and glutamatergic pathways, and brain iron deficiency. 5
Presentation Pattern
RLS typically affects both legs from onset, even if asymmetric in severity, as the diagnostic criteria describe affecting "the legs" (plural). 3