Restless Legs Syndrome (RLS) is a neurological disorder primarily characterized by an unpleasant, hard-to-describe sensation in the legs, accompanied by an irresistible urge to move them. This condition typically worsens during periods of rest and improves temporarily with movement, often making it difficult to fall asleep. RLS is frequently associated with Periodic Limb Movement Disorder (PLMD) during sleep, and both conditions are thought to be different clinical manifestations of a common central nervous system dysfunction.
Epidemiology and Risk Factors
The prevalence of RLS in the general population ranges between 10% and 15%, with its incidence increasing with age. It is more commonly observed in women, and a significant proportion of patients report a family history of the disorder. The genetic transmission is suspected to follow an autosomal dominant pattern.
RLS is categorized into two main types: primary (idiopathic) and secondary. While the exact cause of primary RLS remains unknown, genetic factors are believed to play a crucial role. Secondary RLS, on the other hand, is associated with conditions such as iron deficiency, renal failure, neurological disorders (e.g., Parkinson's disease), pregnancy, rheumatic diseases, and diabetes.
Pathophysiology
Although the exact mechanisms underlying RLS are not fully understood, three primary pathophysiological processes are thought to contribute:
1. Dopaminergic Dysfunction
Hypofunction of the dopaminergic system is considered a central factor in RLS. This theory is supported by the beneficial response observed with treatments involving levodopa and dopamine agonists.
2. Iron Deficiency
Iron is essential for dopamine synthesis and receptor regulation in the brain. Studies have shown that individuals with iron deficiency have lower levels of ferritin in the cerebrospinal fluid, suggesting a strong link between iron deficiency and the development of RLS.
3. Central Nervous System Hyperexcitability
Particularly at the spinal level, increased neural excitability contributes to the involuntary movements seen in both RLS and PLMD.
Clinical Features and Diagnosis
The diagnosis of RLS is based on the following four essential clinical criteria:
- An urge to move the legs, usually accompanied by unpleasant sensations
- Symptom onset or worsening during periods of rest or inactivity
- Partial or complete relief of symptoms with movement
- Symptoms that are more pronounced in the evening or at night
Clinical history, physical examination, and laboratory tests (e.g., serum ferritin levels) support the diagnosis. Polysomnography may be used to assess periodic limb movements during sleep.
Treatment Approaches
The main goals of RLS treatment are to alleviate symptoms and improve quality of life. The treatment strategy depends on whether the condition is primary or secondary.
Pharmacological Therapy
- Dopaminergic Agents
- Medications such as levodopa, pramipexole, ropinirole, and rotigotine are effective in reducing symptoms.
- Iron Supplementation
- In patients with low serum ferritin levels, iron replacement therapy can be beneficial.
- Antiepileptic Drugs
- Gabapentin and pregabalin may help alleviate sensory discomfort.
- Benzodiazepines and Opioids
- These are reserved for treatment-resistant cases, with caution due to the risk of dependency.
Non-Pharmacological Treatment and Lifestyle Modifications
- Sleep Hygiene
- Establishing regular sleep routines and creating a relaxing sleep environment are essential.
- Physical Activity
- Light exercise can alleviate symptoms, although excessive exercise may exacerbate them.
- Dietary Adjustments
- Consumption of caffeine, alcohol, and tobacco should be limited.
