Periodic limb movement disorder (PLMD) is a condition that involves involuntary movement of the skeletal muscles while sleeping. These muscle movements occur periodically throughout the night, resulting in a persistent disruption of sleep, which may lead to sleep deprivation.
The prevalence of PLMS is approximately 4-11% of the adult population, most frequently as a symptom associated with restless legs syndrome (RLS) or other sleeping disorders.
The characteristic symptom of periodic limb movement disorder is episodes of simple, repetitive movements of skeletal muscles during the night, which can wake the individual and disrupt sleep.
The episodes do not usually inhibit an individual from falling asleep but cause them to wake up frequently during the night. They usually last for a few minutes or up to about an hour, with periodic movements every 20 to 40 seconds.
The muscles of the lower leg are most commonly affected, and the movements usually involve tightening or flexing of these muscles. Examples include extension of the big toe or slight bending of the ankle or knee joint. Other areas of the body, such as the arms, may also be affected.
As a result of the reduce sleep quality and quantity, affected individuals may become sleep deprived and feel excessive drowsiness during the day, which can have an impact on their performance at work or in study and their social life. This may cause secondary symptoms, such as depression, poor memory and reduced concentration.
The precise cause of primary PLMD is not currently known, although there are some factors and health conditions that are linked to an increased risk of the condition, which may be involved in the pathophysiology of the condition. These risk and associated factors include:
- Iron deficiency
- Restless legs syndrome
In particular, restless legs syndrome (RLS) is related to PLMD and is thought to be involved as a causative factor. More than 80% of individuals with RLS have PLMD, although many patients with PLMD are not affected by RLS.
When a patient presents with reported symptoms that may be indicative of periodic limb movement disorder, there are several diagnostic techniques that can be used to differentiate the condition from other similar disorders.
A sleep diary where the patient records sleeping habits and the periods of disrupted sleep during the night can help to establish the characteristics of the condition.
A polysomnogram is an overnight sleep study that monitors the sleep pattern of the individual, which is used to confirm the diagnosis of the condition. Other tests such as urine or blood examinations may also be required in some instances to rule out other related health condition.
The aim of treatment of periodic limb movement disorder is to reduce the muscular movements during sleep, to allow patients to get adequate sleep during the night.
As PLMD typically occurs as a secondary condition that results from an underlying cause or health condition, the root cause should be addressed first in the management of the condition.
The idiopathic form of the PLMD is usually considered to be chronic and treatment does not appear to have a significant effect to modify the disease and symptoms.
Good sleep hygiene practices should be encouraged, including the maintenance of a regular sleep schedule and avoidance of stimulant such as caffeine, alcohol and nicotine before bed.
Pharmacological therapy to aid sleep may also be beneficial in some cases, including some dopaminergic agents, benzodiazepines or anticonvulsant drugs to reduce muscle movements and aid sleep.