Myoclonus - Periodic Limb Movements

Myoclonus is muscle twitching that oftens occur as people fall asleep. The sudden twitch startles many people out of sleep.

Myoclonus is a symptom, not a disease. It refers to sudden, involuntary jerking of a muscle or group of muscles. People cannot control their twitching. It never happens during REM sleep, when the leg muscles are paralyzed. The kicking lasts from several minutes to hours. Sometimes the person knows about it; sometimes not - the person only knows about it when someone else notices or from kicked over bedding material. Note that hypnic jerks are not myoclonus; pretty much everyone occasionally has hypnic jerks when falling asleep. Hypnic jerks are perfectly normal and not worth doing anything medical about.

Myoclonic twitches or jerks usually are caused by positive myoclonus refers to sudden muscle contractions, negative myoclonus to muscle relaxation.

Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Myoclonus sometimes occurs in response to an external event or when a person attempts to make a movement. The twitching cannot be controlled by the person experiencing it.

Most people experience sleep myoclonus at one time or another. Hiccups are also a form of normal myoclonus.

The large majority of sleep myoclonus cases do not need treatment. In bad cases, doctors do have some options.

Treatment of myoclonus may include anti-seizure drugs. Many of these drugs, which include barbiturates, clonazepam, phenytoin, primidone, and sodium valproate, are also used to treat epilepsy. Even with treatment, muscle contractions may persist. If myoclonus is due to a side effect of medication, discontinuing the drug is the best treatment option.

The first drug of choice is usually clonazepam, which as a tranquilizer has serious side effects. Because myoclonus has complex origins, reasearchers feel that no one drug works and that multiple drugs may be necessary.

Restless leg syndrome is less common, affecting only 5% of the population. The main characteristic of RLS is a crawly feeling in the legs when the person is lying down. Both myoclonus and RLS cause insomnia. They are more common in men than women and tend to run in families.

Other neurologic conditions may mimic the muscle contractions of myoclonus. But these are more accurately referred to as:

• Tics — a repetitive movement that's difficult, if not impossible, to control
• Chorea — involuntary, complex body movements
• Dyskinesia — difficulty in performing voluntary movements
• Restless legs syndrome — jerking leg movements during sleep
  

Sleep Disorders

Dyssomnias

Parsomnias