QUICK REFERENCE #41: What is restless legs syndrome?

Restless legs syndrome (RLS) is a neurologic movement disorder most commonly characterized by very strong urges to move the legs, usually due to unpleasant leg sensations. These sensations worsen during periods of inactivity and often interfere with sleep.

The following content is adapted primarily from a guide produced by the National Center on Sleep Disorders Research (1). Diagnostic criteria noted below were developed by the International Restless Legs Syndrome Study Group (2). See SOURCES, below.

Although most patients with RLS experience unpleasant sensations in their legs, the sensations may also occur in the arms or elsewhere. RLS can be described as an agitated inability to rest that can have a negative impact on the quality of life due to chronic sleep deprivation, discomfort while awake, and stress. Terms used by patients to describe RLS sensations include the following: creeping; itching; tugging; aching; painful; pulling; restless; burning; crawling; searing; like worms or bugs crawling under the skin; like water flowing; like an electric current. Limited data indicate that 2 to 15 percent of the population experience RLS symptoms. RLS can occur in children, but it is more common in adults.

Primary RLS is a central nervous system disorder. Although RLS is not caused by psychiatric factors or by stress, it can be exacerbated by these conditions.

Secondary causes of RLS include iron deficiency, neurologic lesions, pregnancy (with symptoms usually subsiding within a few weeks postpartum), uremia (in which symptoms may be particularly uncomfortable when patient is confined to a resting position for dialysis), and medications or other substances (eg, tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), lithium, dopamine antagonists, caffeine, and alcohol).

A diagnosis of RLS is based primarily on clinical findings and on the patient’s history. Patients often, however, do not initiate discussion of RLS symptoms. It is, therefore, helpful to ask questions about general sleep and sleep-related functioning as well as questions more specific to RLS. In addition, a physical examination is recommended so that the clinician may rule out any other disorders, or may identify secondary causes. Specifically, a neurological exam with an emphasis on spinal cord and peripheral nerve function can be conducted. A vascular exam can be conducted to rule out vascular disorders. A sleep study (polysomnography) is usually not needed to establish the presence of RLS. RLS diagnostic criteria and differential diagnosis considerations appear below.

Minimal Criteria for the Diagnosis of Restless Legs Syndrome

1. A compelling urge to move the limbs, usually associated with paresthesias/dysesthesias (ie, uncomfortable sensations on the skin such as tingling, numbness, burning).

2. Motor restlessness, as seen in activities such as floor pacing, tossing and turning in bed, and rubbing the legs.

3. Symptoms worse or exclusively present at rest (ie, lying, sitting) with variable and temporary relief by activity.

4. Symptoms worse in the evening and at night.

Other associated features commonly found in RLS, but not required for diagnosis, include the following:

• Sleep disturbance and daytime fatigue.
• Normal neurological examination in primary RLS.
• Involuntary, repetitive, periodic, jerking limb movements, either in sleep or while awake and at rest. (This feature refers to periodic limb movements [PLM], also known as periodic limb movements of sleep (PLMS) or nocturnal myoclonus, which may be associated with RLS. PLM are stereotyped, repetitive flexions of the limbs [legs alone or legs more than arms] usually occurring during sleep. They occur periodically on an average of every 20 seconds. The most common movement is a dorsiflexion of the ankles and flexion of the knees or hips.)

SOURCES:
(1) Restless Legs Syndrome: Detection and Management in Primary Care. National Institutes of Health, 2000. [Produced by the National Center on Sleep Disorders Research (NCSDR) of the National Heart, Lung, and Blood Institute (NHLBI) in collaboration with the Restless Legs Syndrome Foundation.]
http://www.nhlbi.nih.gov/health/prof/sleep/rls_gde.htm

(2) The International Restless Legs Syndrome Study Group. [Walters AS. Toward a better definition of the restless legs syndrome. Movement Disorders, 10:634-642, 1995.]

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