This condition is characterized by periodic episodes of repetitive and highly stereotyped limb movements that occur during sleep. The movement usually occurs in the legs and consists of extension of the big toe in combination with partial flexion of the ankle, knee, and sometimes hip. Similar movements can occur in the upper limbs. The movements are often associated with a partial arousal or awakening; however, the patient is usually unaware of the limb movements or the frequent sleep disruption. Between the episodes, the legs are still. Marked night-to-night variability can occur in the number of movements.

A history of frequent nocturnal awakenings and unrefreshing sleep may exist. Patients unaware of the sleep interruptions may have symptoms of excessive sleepiness. It is probable that the nature of the patient’s complaint is affected by the frequency of the movement as well as the associated awakenings.

The disorder can produce anxiety and depression. While the natural history of this disorder in unknown, it appears to increase in prevalence with advancing age. It appears to be rare in children and progresses with advancing age to become a common finding in up to 34 percent of patients over the age of 60 years.

This disorder can accompany narcolepsy and sleep apnea. It can be evoked by a variety of other medical conditions, such as chronic uremia and other metabolic disorders. Tricyclic antidepressants and monoamine oxidase inhibitors can induce or aggravate this disorder, as does withdrawal from a variety of drugs, such as anticonvulsants, benzodiazepines, barbiturates, and other hypnotic agents.