General information about restless legs syndrome and periodic limb movements of sleep/wakefulness

Restless legs syndrome and periodic limb movements of sleep/wakefulness often coexist, and are common causes of insomnia and excessive daytime sleepiness.

Periodic limb movements are repetitive flexion of the legs (and occasionally the arms) and dorsiflexion and fanning of the toes—these movements can occur during sleep or when awake. Periodic limb movements occur in 80% of patients with restless legs syndrome. However, periodic limb movements can be normal (eg in elderly people) and are not specific for restless legs syndrome.

Restless legs syndrome is diagnosed using clinical criteria, and a sleep study is not usually needed. The condition can be idiopathic or secondary—causes include iron deficiency, pregnancy and end-stage kidney disease. Some drugs (eg antidepressants, antihistamines) can exacerbate the condition.

Typically, patients complain of limb (usually leg) discomfort at rest, followed by an urge to move the affected part. Often patients cannot describe their symptoms, but may describe the sensation as creeping, crawling, itching, burning, searing, tugging, pulling, drawing, aching, hot and cold, electric current–like, restless or painful. Symptoms affect both arms and legs in about 50% of patients; symptoms confined to the arms are uncommon. Sometimes only one side of the body is affected.

Usually, symptoms occur when the patient has been lying quietly, and last for a few minutes or an hour. Symptoms can also occur when the patient is sitting quietly, but this is rare. When the patient is more mentally rested and physically quiet, the symptoms are more intense. The syndrome is worse from the evening to the early hours of the morning, whether or not the patient is asleep. This circadian pattern can be lost in severe cases. Shift work, medication and sleep disorders may modify the pattern.

Voluntary movement (not necessarily of the affected limb) gives prompt relief, but the effect is temporary. Characteristically, to get relief the patient moves about in their bed or chair, gets up and paces about, or stretches or rubs the limbs. Sometimes, placing the limbs on a cold or hot surface gives the same relief as movement.