Periodic limb movement disorder (PLMD) is a sleep disorder where the patient moves limbs involuntarily and periodically during sleep, and has symptoms or problems related to the movement. PLMD should not be confused with restless legs syndrome (RLS), which is characterized by a voluntary response to an urge to move legs due to discomfort. PLMD, on the other hand, is involuntary, and the patient is often unaware of these movements altogether. Periodic limb movements (PLMs) occurring during the daytime period can be found but are considered a symptom of RLS; only PLMs during sleep can suggest a diagnosis of PLMD.
Periodic limb movement disorder is characterized by recurrent episodes of frequent limb movements while sleeping. It mostly occurs in the lower body, such as the toes, ankles, knees, and hips. It can also appear in the upper extremities in some cases. These movements can lead the patient to wake up, and if so, sleep interruption can be the origin of excessive daytime sleepiness.
PLMD is characterized by increased periodic limb movements during sleep, which must coexist with a sleep disturbance or other functional impairment, in an explicit cause-effect relationship. PLMs seem to be common features within many people, and identifying whether or not these movements are clinically relevant for a distinct diagnosis of PLMD remains a challenge for clinical and scientific fields. PLMS is often a symptom of RLS but evidence for differences between those two sleep disorders was found in literature. Sleep structure differed when RLS patients had significantly more REM sleep and less stage 1 sleep than PLMD patients. Besides, PLMI was significantly higher in patients with PLMD.
Causes
It is mostly unknown what causes PLMD, but in many cases the patient also has other medical problems such as Parkinson's disease or narcolepsy. Medical agents must be taken into consideration: several psychopharmacological drugs (serotonergic and tricyclic antidepressants, venlafaxine, and mirtazapine) heighten the risk of PLMD. For women, 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 legs syndrome.
Diagnosis
360px|thumb|5 minute segment of a polysomnogram, demonstrating 7 PLMs with arousals
People with PLMD often do not know the cause of their excessive daytime sleepiness, and their limb movements are reported by a spouse or sleep partner. PLMD cannot be diagnosed by polysomnogram (PSG) sleep study alone; it is necessary to obtain a full medical history and take into account all available information. There are some updates from ICSD-2. The diagnosis is stricter. Other dopaminergic agents such as co-careldopa, co-beneldopa, pergolide, or lisuride may also be used. These medications decrease or eliminate both the leg jerks and the arousals. These medications are also successful for the treatment of restless legs 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 nighttime to daytime.
Clonazepam in doses of 1mg has been shown to improve objective and subjective measures of sleep.
Hypothesis was presented for supplementation of magnesium use for PLMD improvement due to evidence for therapeutic effects of magnesium on normal magnesium level patients with insomnia and RLS. but is more common in the elderly, especially females, with up to 11% experiencing symptoms. PLMD appears to be related to restless legs syndrome (RLS) - a study of 133 people found that 80% of those with RLS also had PLMS. However, the opposite is not true: many people who have PLMS do not also have restless legs syndrome.
PLMD is an uncommon childhood disorder. Based on adult criteria and PSG analysis, studies showed the prevalence of isolated PLMD in the child population with no other comorbidity to be about 1.2 to 1.5%. There was also evidence for 5.6 to 7.7% of children with PLMI > 5/hr. Periodic limb movements during sleep are associated with a lower quality of life in children with monosymptomatic nocturnal enuresis
See also
- Hypnic jerk