Restless Legs Syndrome

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Diagnosing RLS

As RLS is a collection of disorders, there are no classic physical findings, no conclusive blood assays, and no standard radiological or sleep studies to diagnose RLS. Because there is no single definitive biomarker, the diagnosis of RLS can only be established based on clinical history. The lack of an objective test has led to frequent underdiagnosis and misdiagnosis. In an attempt to more clearly define RLS, the International Restless Legs Syndrome Study Group (IRLSSG) developed RLS diagnostic criteria in 1995. In 2003 a consensus panel at the National Institutes of Health (NIH) modified these criteria to their current form. Meeting these four standard criteria is necessary and sufficient to make the diagnosis of RLS:

Figure 1

RLS Risk Factors

  • Family history present in 50-70% of patients with RLS
  • Prevalence increases with age
    More prevalent in women than men
  • Smokers
  • People that exercise <3 hours per month
  • Diabetics 4 times as likely to have RLS [10]

RLS Differential Diagnosis

  • Neuropathic pain syndromes
  • Peripheral neuropathy
  • Arthritis
  • Nocturnal leg cramps
  • Restless insomnia
  • Painful legs and moving toes
  • Arterial insufficiency
  • Drug-induced akathisia [11]

RLS is often misdiagnosed, as many sleep and movement disorders share similar characteristics. Lots of people habitually shake their legs or tap their feet because of a nervous habit, drinking too much coffee, etc. Other conditions such as nighttime leg cramps, peripheral neuropathy, positional discomfort, etc. prevent falling asleep and can be confused with RLS. The treating physician must be careful to rule out all of these conditions.

Children are especially hard to diagnose because the physician relies on the patient’s accurate description of the symptoms. RLS in children is frequently mislabeled as Attention Deficit Hyperactivity Disorder (ADHD) or growing pains.

Diagnostic accuracy can be improved in borderline or atypical cases by asking about RLS Risk Factors, supportive clinical features and by performing the Suggested Immobilization Test (SIT) and Polysomnogram (PSG). Supportive clinical features include a positive family history, positive response to dopaminergic therapy, and the presence of Periodic Leg Movements (PLMs) (during wakefulness or sleep). The SIT is best performed in the evening, and involves measuring sensory discomfort while the patient sits immobilized. A PSG is performed in the sleep lab, and is used to record PLMs that occur during wake (PLMW) and sleep (PLMS). These leg movements are seen in approximately 80-90% of RLS patients. The presence of these supportive clinical features or positive SIT / PSG help to establish the diagnosis of RLS, but their absence does not exclude the diagnosis of RLS. [9]

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