Restless legs syndrome

Summarized by Robert W. Griffith, MD
October 2, 2000 (Reviewed: February 1, 2003)

Introduction

Nearly all physicians have heard of the restless legs syndrome (RLS), but relatively few know much about its etiology, diagnosis, and treatment. It is probably much commoner than most people think; reports indicate that between 2% and15% of the USA population may suffer from this somewhat distressing disorder. A recent NIH working group report on RLS is therefore timely. It provides an up-to-date summary of what is known of its detection and management.

Although RLS can occur in children, it is commonly encountered first in adulthood, and its prevalence increases with age. It affects either sex. There is a high familial incidence of so-called primary RLS, but certain conditions appear to precipitate the condition: iron deficiency, spinal cord and peripheral nerve lesions, uremia, and pregnancy. If these can be reversed, the symptoms improve. Worsening or unmasking of RLS has been reported after certain medications: tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), lithium, and dopamine antagonists. Caffeine has also been blamed for exacerbations.

Diagnosis

The subject's description of symptoms provides the diagnosis. While the patient may use terms like 'creeping', 'crawling', 'itching', 'burning', 'searing', 'tugging', and so on, the following criteria are those used for diagnosis:

1. A compelling urge to move the limbs, usually associated with paresthesia
2. Restless movements such as floor pacing, tossing and turning in bed, rubbing the legs.
3. Symptoms worse (or only present) at rest, relieved by activity
4. Symptoms worse in the evening and at night

Sleep disturbance, with daytime fatigue, is commonly reported, along with involuntary repetitive jerking leg movements, while asleep or at rest. The neurological exam is usually normal (unless the RLS is secondary to a neurological lesion).

Mention must be made of periodic limb movements in sleep (PLMS), also known as nocturnal myoclonus, which can be associated with RLS. These repetitive flexions of the limbs during sleep occur periodically every 20 seconds.

Physical examination is usually normal. Laboratory investigations should include: serum ferritin level (to exclude iron deficiency), serum urea, and blood sugar (to exclude diabetic neuropathy). The differential diagnosis includes nocturnal leg cramps (these are usually painful, focal, and unilateral), akathisia (not evening/sleep related, but associated with neuroleptic or dopamine-blocking drugs), peripheral neuropathy (unrelated to time of day, not relieved by movement, mainly sensory symptoms), and deep vein thrombosis.

Treatment

Treatment of RLS must be individualized; it often involves considerable trial and error. A number of drugs from different classes can provide benefit, but there is no obvious 'treatment of choice'.

Mild symptoms may not require medication; hot baths, massage, exercising, or reduction in caffeine use may provide adequate benefit.

Dopamine precursors (e.g. carbidopa-levodopa) are often given initially, and are likely to be effective. However, they can cause 'augmentation' - worsening of symptoms or their appearance earlier in the day or in a different part of the body - as well as insomnia and gastrointestinal problems.

Dopamine agonists (pergolide, bromocriptine) are reported as being useful, but can also cause augmentation, nausea and sleeplessness.

Benzodiazepines (clonazepam, temazepam) can be helpful, but may cause cognitive impairment in elderly subjects.

Opioid derivatives (codeine, propoxyphene, tramadol) should be reserved for severe cases, and be used intermittently because of the risks of addiction, constipation, and urinary retention.

Other medications that can be tried include anticonvulsants, clonidine, vitamin E, and folic acid. Iron deficiency should be addressed, diabetes tightly controlled, and renal failure treated. Transcutaneous electric nerve stimulation just before bedtime may help some sufferers of RLS with PLMS, reducing nighttime leg jerking.

Comment

Improved knowledge of this distressing syndrome can lead to effective management in the majority of sufferers, according to the working group. As patients often fail to mention their RLS symptoms spontaneously, the aware physician may do well to ask questions about sleep patterns, as well as specific enquiries for RLS diagnostic symptoms.

Source

• Restless legs syndrome. Detection and management in primary care.  National Center on Sleep Disorders Research Working Group., NIH Publication No 00-3788, 2000, vol. , pp. --

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