Nocturnal myoclonus

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Periodic Limb Movement Disorder (PLMD), also called nocturnal myoclonus, is a sleep disorder where the patient moves involuntarily during sleep. It can range from a small amount in the ankles and toes to wild flailing of all four limbs. These movements, which are more common in the legs than arms, occur for between 0.5 and 10 seconds, recurring at intervals of 5 to 90 seconds. A formal diagnosis of PLMD requires three periods during the night, lasting from a few minutes to an hour or more, each containing at least 30 movements followed by partial arousal or awakening.

PLMD is a cause of insomnia and daytime sleepiness. The incidence of this disorder increases with age. It is estimated to occur in 5% of people age 30 to 50 and in 44% of people over the age of 65. As many as 12.2% of patients suffering from insomnia and 3.5% of patients suffering from excessive daytime sleepiness may experience PLMD.

It is related to restless leg syndrome (RLS) in that 80% of people with RLS also have PLMD. However, most people with PLMD do not experience RLS.

This disorder has made its way into popular culture, being referred to as "jimmy legs" and "jimmy arms" in an episode of Seinfeld, and has been known to cause couples to sleep in separate beds. In both examples, one subject suffers from PLMD severely enough to disturb the sleep of the other subject.

[edit] Treatment

PLMD is treated by medications aimed at reducing or eliminating the leg jerks or the arousals. Dopaminergic agents such as carbidopa/levodopa, pergolide, and a newer drug, pramipexol, are the treatment of choice for PLMD, as they decrease or eliminate both the leg jerks and the arousals. These medications are also successful for the treatment of RLS restless leg syndrome. In one study, carbidopa/ levodopa was superior to propoxyphene in decreasing the number of leg kicks and the number of arousals per hour of sleep. However, carbidopa/levodopa and, to a lesser extent, pergolide may shift the leg movements from the nighttime to the daytime.

[edit] References

Ancoli-Israel S, Kripke DF, Klauber MR, Mason WJ, Fell R, Kaplan O. Periodic limb movements in sleep in community-dwelling elderly. Sleep, 1991;14(6):496-500.
Periodic Limb Movements in Sleep Am I Res Crit Care Med. 1998;157:858-865.
Kaplan PW, Allen RP, Buchholz DW, Walters JK. A double-blind, placebo-controlled study of the treatment of periodic limb movements in sleep using carbidopa/levidopa and propoxyphene. Sleep. 1993;16(8):717-723.