Restless Leg Syndrome: An Urge to Move Triggered by Rest

Which of the following symptoms is one of the diagnostic features of restless legs syndrome (RLS)?
A.    Pain in the lower extremities that is induced by excessive physical activity
B.    Vermicular movements in the lower extremities experienced usually just prior to sleep onset
C.    An urge to move the upper or lower extremities, usually induced by rest
D.    A throbbing sensation that leads to a feeling of inner restlessness
E.    None of the above

Answer: C-An urge to move the upper or lower extremities, usually induced by rest

RLS was first described in 1672 by Sir Thomas Willis, and its features were further defined by Karl Ekbom in 1945. Its hallmark symptoms are best remembered through the URGE mnemonic:

• Urge to move the legs, usually associated with unpleasant leg sensations
• Rest induces symptoms
• Getting active (physically and mentally) brings relief
• Evening and night make symptoms worse

Unpleasant sensations, although not critical for the diagnosis, are highly diverse in scope and can include pain, shock-like feelings, pulling, throbbing, itching, and ants crawling, among others.  Many patients also suffer from sleep disturbances, which are the most frequent reasons for presentation to medical professionals. 

RLS is fairly common; around 3% of the population suffer from a moderate to severe form of the condition, which entails having symptoms 2 or more times per week. However, RLS is poorly identified in these patients; therefore, inquiry regarding an irresistible urge to move the extremities is helpful in increasing the diagnostic yield. Although periodic limb disorder activity (nocturnal myoclonus) is common in RLS sufferers, sleep studies are not necessary to establish the diagnosis. 

Once RLS is identified, evaluation entails searching for secondary causes of the syndrome; these include, but are not limited to, kidney disease, anemia (especially iron deficiency), pregnancy, and gastric surgery. Certain medications, such as antipsychotics, antidepressants, antiemetics, and antihistamines, may also precipitate RLS symptoms. Treatment of the underlying cause is then undertaken. If the syndrome is primary, specific treatments are available and usually highly effective.

Take home points:
1. RLS is common in patients presenting with the complaint of disturbed sleep, but underdiagnosed
2. The diagnosis of RLS is symptom-based

 

References:
1. Allen RP, Picchietti D, Hening WA, et al. Restless legs syndrome: diagnostic criteria, special considerations, and epidemiology: a report from the restless legs syndrome diagnosis and epidemiology workshop at the National Institutes of Health. Restless Legs Syndrome Diagnosis and Epidemiology Workshop at the National Institutes of Health; International Restless Legs Syndrome Study Group. Sleep Med. 2003;4:101-119.
2. Montplaisir J, Allen R, Walters A, et al. In: Kryger M, Roth T, Dement W, eds. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia: Elsevier, Saunders; 2005:839-852.
3. Ekbom KA. Restless legs syndrome. Neurology. 1960;10:868-873.