Periodic limb movement disorder (PLMD) is a condition that causes patients to unconsciously flex or jerk their legs and arms during sleep. The movement may sporadically awaken the patient, which can lead to insomnia or severe daytime sleepiness.

PLMD is marked by characteristic movements that occur during sleep. Patients tend to upwardly flex the big toe, as well as the ankle, knee or hip as often as every 20 seconds. A patient’s legs may also uncontrollably twitch, jerk or kick while sleeping. Some patients may also move their arms. These flexes may occur over a few minutes to several hours.

The cause of PLMD is unknown, although it may be related to abnormalities in the patient’s brain stem or in levels of the neurotransmitter dopamine. When it occurs on its own, the disorder is more prevalent in patients older than 40 and those with poor sleep hygiene (conditions that promote sleep). PLMD may also occur in conjunction with other conditions, such as restless leg syndrome, Parkinson’s disease, narcolepsy and attention deficit hyperactivity disorder. Patients may also develop the condition when taking medications that affect dopamine levels.

A sleep study is necessary to confidently diagnose PLMD. While the patient sleeps, an electroencephalogram records the electrical activity of the brain through electrodes placed on the skin. In addition, laboratory personnel observe the sleeping patient’s limb movements.

Medications are available to treat PLMD, although treatment is typically only necessary if it causes insomnia. There is no cure for PLMD, but sedatives and dopaminergics (drugs that simulate the behavior of dopamine) tend to ease PLMD symptoms. The medications must be used regularly for proper treatment of the disorder. Because the causes of PLMD are largely unknown, it is not always possible to prevent the condition, although some behavioral changes may help.