Periodic limb movement disorder
Nocturnal myoclonus, also called Periodic Limb Movement Disorder (PLMD), is a sleep disorder where the patient moves limbs involuntarily during sleep and has symptoms or problems related to the movement. If the patient moves limbs during sleep but there are no consequences, it is simply called periodic limb movements of sleep (PLMS). Not all patients with PLMS have PLMD (in fact, most people with PLMS do not have a disorder requiring any treatment).
PLMS is diagnosed with the aid of a polysomnogram or PSG. PLMD is diagnosed by first finding PLMS on a PSG, then integrating that information with a detailed history from the patient and/or bed partner. PLMS can range from a small amount of movement 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 5 seconds, recurring at intervals of 5 to 90 seconds. A formal diagnosis of PLMS 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.
PLMS can cause insomnia and daytime sleepiness. It is estimated to occur in approximately 4% of adults (aged 15-100)[1], but is more common in the elderly, especially females, with up to 11% experiencing symptoms.[2]. PLMS is related to restless leg syndrome (RLS) - a study of 133 people found that 80% of those with RLS also had PLMS.[3]
PLMS has made its way into popular culture, being referred to as "jimmy legs" and "jimmy arms" in an episode of the television sitcom Seinfeld, and has been known to cause couples to sleep in separate beds. In both examples, one subject suffers from PLMS severely enough to disturb the sleep of the other subject.[4]
Factors that increase the likelihood of PLMD in the absence of restless leg syndrome include being a shift worker, snoring, coffee drinking, stress, and use of hypnotics. Being a woman, the presence of musculoskeletal disease, heart disease, obstructive sleep apnea, cataplexy, doing physical activities close to bedtime and the presence of a mental disorder were significantly associated with having a higher risk of both PLMD and restless leg syndrome.[1]
Treatment
Nocturnal myoclonus is treated by medications aimed at reducing or eliminating the leg jerks or the arousals. Non-ergot derived dopaminergic drugs (pramipexole and ropinirole) are preferred. Other dopaminergic agents such as co-careldopa, co-beneldopa, pergolide, or lisuride may also be used. These drugs 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, co-careldopa was superior to dextropropoxyphene in decreasing the number of leg kicks and the number of arousals per hour of sleep. However, co-careldopa and, to a lesser extent, pergolide may shift the leg movements from the nighttime to the daytime.[5]
Clonazepam, (Klonopin), in doses of 1mg has been shown to improve objective and subjective measures of sleep.[6]
PLMD can be caused by a lack of calcium, iron or magnesium. Checking for deficiencies of minerals in the body is a logical first step.
References
- ^ a b J Psychosom Res. 2002 Jul;53(1):547-54. Prevalence of restless legs syndrome and periodic limb movement disorder in the general population. Ohayon MM, Roth T.
- ^ J Psychosom Res. 2004 May;56(5):543-8. Restless legs syndrome and periodic limb movement disorder in the elderly. Hornyak M, Trenkwalder C.
- ^ Clinical, polysomnographic, and genetic characteristics of restless legs syndrome: a study of 133 … J Montplaisir, S Boucher, G Poirier, G Lavigne, O … - Mov Disord, 1997
- ^ * http://www.seinfeldscripts.com/TheMoney.html The Money, a Seinfeld Episode in which Kramer describes his girlfriend having "the Jimmy Legs"
- ^ 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.
- ^ Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) Acute placebo-controlled sleep laboratory studies with clonazepam. European Neuropsychopharmacology , Volume 11 , Issue 2 , Pages 153 - 161. M . Saletu