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:
- An urge to move the legs, usually accompanied or caused by uncomfortable or unpleasant sensation in the legs. The sensations are located deep within the leg; most often in the calf, but not infrequently within the thigh as well. Symptoms occasionally occur in the feet or upper extremities. Most patients find they cannot describe the nature of their sensations. Dr. Ekbom felt that “this is evidently due to the fact that the sensations do not resemble any known phenomenon that can be used as a comparison.” [8] In our experience, the most frequently used description of the sensations is “I can’t describe it.” The inability to accurately describe their sensations can be a source of frustration to the patient and to physicians not familiar with RLS. It can also be a barrier to adequate diagnosis and treatment.
- Symptoms begin or worsen during rest or periods of inactivity such as lying down or sitting. Patients are typically symptom-free when they are up and about. The symptoms appear during any period of prolonged daytime inactivity, especially if the patient is lying down or reclining. Formerly pleasant leisure activities become dreaded. Long car rides or plane trips are intolerable. Movies, theatre, concerts, church services, etc. can no longer be enjoyed and are often avoided. Patients begin scheduling their life around their symptoms. Eventually, they can become a prisoner of their RLS.
Symptoms are partially or totally relieved by movements such as walking at least as long as the activity continues. Effective movements vary from wiggling the legs or tossing and turning in bed to stretching exercises or pacing the floor. The movements are purely voluntary, though the patient feels “compelled” to move the legs, as the movement temporarily relieves the horrible sensations. The improvement with movement is immediate and continues for as long as the leg movement continues. The desire to relieve the symptoms can lead to compulsions involving excessive leg movements. Patients can become overwhelmed by the sensations and the compulsion to relieve them.- Symptoms are worse in the evening or night than during the day. Nocturnal sleep disturbance is the chief morbidity associated with RLS. As RLS symptoms are usually stronger at bedtime, sleep-onset insomnia is common. RLS sufferers often find they cannot fall asleep until the early morning hours. Patients with severe RLS experience nightly attacks that lead to chronic sleep-deprivation. In severe cases, patients can experience symptoms both day and night.
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]
