What is Restless Legs Syndrome (RLS)?
Restless Legs Syndrome (RLS), also known as Willis-Ekbom Disease, is a neurological sensorimotor disorder characterized by an irresistible urge to move the legs, typically accompanied by uncomfortable sensations that worsen during rest and are relieved by movement, with symptoms predominantly occurring in the evening or at night. 1
Diagnostic Criteria
RLS is diagnosed clinically based on five essential criteria that must all be present 2:
An urge to move the legs usually accompanied by uncomfortable and unpleasant sensations in the legs (sometimes arms or other body parts may be involved)
Symptoms begin or worsen during rest or inactivity such as lying down or sitting
Symptoms are partially or totally relieved by movement such as walking or stretching, at least as long as the activity continues
Symptoms are worse in the evening or night than during the day (circadian pattern)
Symptoms are not solely accounted for by another medical or behavioral condition - this is critical to exclude "RLS mimics" including leg cramps, leg edema, venous stasis, positional discomfort, muscle aches, habitual foot tapping, and arthritis 2
Clinical Significance and Prevalence
Clinically significant RLS (occurring at least once weekly with moderate distress) affects 2-3% of adults and 0.5-1% of children 1. The condition is approximately 50% more prevalent in females, partly related to pregnancy, and is more common in those of northern European heritage 1.
Impact on Quality of Life
The primary morbidity of RLS is insomnia, with difficulty falling or staying asleep present in roughly 90% of people with RLS 1. The disorder causes significant distress or impairment in social, occupational, educational, or other important areas of functioning through its impact on:
- Sleep quality
- Energy and vitality
- Daily activities
- Behavior and cognition
- Mood 2
Clinical Course Classification
RLS severity varies considerably 2:
- Chronic-persistent RLS: Symptoms occur on average at least twice weekly for the past year when untreated
- Intermittent RLS: Symptoms occur less than twice weekly for the past year, with at least 5 lifetime events
Symptoms can range from isolated occurrences during prolonged sitting to daily, near around-the-clock discomfort and movement 1.
Associated Findings
Periodic Limb Movements during Sleep (PLMS) are commonly present in RLS patients - these are brief (0.5-10 seconds), recurrent lower extremity movements occurring roughly every 15-30 seconds, particularly during the first 4 hours of sleep. These movements are invariably associated with elevations in heart rate and blood pressure 1.
Important Diagnostic Pitfalls
Without proper differential diagnosis, 16% of subjects who do not have RLS will be misclassified as having RLS 2. The key is criterion #5 - actively excluding mimics through careful clinical history, as there is no objective test to confirm RLS diagnosis 1.
In children, diagnosis is particularly challenging as they may have difficulty describing symptoms. Growing pains, leg cramps, and behavioral issues are common mimics in the pediatric population 1.
Pathophysiology
The underlying mechanisms involve central dopaminergic dysfunction and impaired iron metabolism in the brain 3. Iron deficiency is now recognized as a core pathophysiological target, even in the absence of overt anemia 4.