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Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are characterized by abnormal motions of and sometimes sensations in the lower or upper extremities, which may interfere with sleep.
PLMD and RLS are more common during middle and older age; > 80% of patients with RLS also have PLMD.
The mechanism is unclear but may involve abnormalities in dopamine neurotransmission in the CNS. The disorders can occur in isolation or during drug withdrawal, with use of stimulants or certain antidepressants, during pregnancy, or in patients with chronic renal or hepatic failure, iron deficiency, anemia, and other disorders. In primary RLS, heredity may be involved; more than one third of patients with primary RLS have a family history of it. Risk factors may include a sedentary lifestyle, smoking, and obesity.
Symptoms and Signs
PLMD is characterized by repetitive (usually every 20 to 40 sec) twitching or kicking of the lower or upper extremities during sleep. Patients usually complain of interrupted nocturnal sleep or excessive daytime sleepiness. They are typically unaware of the movements and brief arousals that follow and have no abnormal sensations in the extremities.
RLS is a sensorimotor disorder characterized by an irresistible urge to move the legs, usually accompanied by paresthesias (eg, creeping or crawling sensations) and sometimes pain in the upper or lower extremities, which are more prominent when patients are inactive or recline, and peak in severity around bedtime. To relieve symptoms, patients move the affected extremity by stretching, kicking, or walking. As a result, they have difficulty falling asleep, repeated nocturnal awakenings, or both.
Diagnosis
Diagnosis may be suggested by the patient's or bed partner's history. Polysomnography is necessary to confirm the diagnosis of PLMD, which is usually apparent as repetitive bursts of electromyographic activity. Polysomnography may be also done after RLS is diagnosed to determine whether patients also have PLMD, but polysomnography is not necessary for diagnosis of RLS itself.
Patients with either disorder should be evaluated medically for disorders that can contribute (eg, with blood tests for anemia and iron deficiency and with hepatic and renal function tests).
Treatment
Numerous drugs (eg, dopaminergic drugs, benzodiazepines, anticonvulsants, vitamins and minerals) are used; only dopaminergic drugs are specific for RLS.
Dopaminergic drugs, although often effective, may have adverse effects such as augmentation (symptoms are felt earlier in the day), rebound (symptoms worsen after stopping the drug or after effects of the drug dissipate), nausea, orthostatic hypotension, and insomnia.Two D2 and D3 dopamine agonists, pramipexole and ropinirole, are effective and have few serious adverse effects. Pramipexole 0.125 mg po is given 2 h before onset of severe symptoms and increased, as needed, by 0.125 mg po q 2 nights until symptoms are relieved (maximum dose 0.5 mg). Ropinirole 0.25 mg po is given 1 to 3 h before symptoms occur and is increased, as needed, by 0.25 mg nightly (maximum dose 4 mg).
Benzodiazepines may improve sleep continuity but do not reduce limb movements; they should be used cautiously to avoid tolerance and daytime sleepiness. Gabapentin beginning with 300 mg at bedtime can help when RLS is accompanied by pain. Dose is increased by 300 mg weekly (maximum dose 2700 mg). Opioids may also work but are used as a last resort because of tolerance, adverse effects, and abuse potential. Ferritin levels should be obtained and, if low (< 50 μg/L), supplementation with ferrous sulfate 325 mg with 100 to 200 mg of vitamin C at bedtime is warranted. Patients should exercise good sleep hygiene.
Last full review/revision April 2008 by Karl Doghramji, MD
Content last modified April 2008
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