VI. Sleep-Related Movement Disorders
The movement disorders include periodic limb movement disorder, restless legs syndrome, bruxism, and sleep-related leg cramps. These disorders cause disrupted nighttime sleep and daytime sleepiness and fatigue.
Restless Legs Syndrome
Restless legs syndrome (RLS) is described as an unpleasant deep, creeping, or crawling sensation in the calves that occurs more frequently near bedtime, and particularly when the individual is sitting or lying down. The abnormal sensation is relieved, at least temporarily, by movement. Occasional patients have similar symptoms in the arms, and some patients have daytime symptoms. Restless legs syndrome usually causes difficulty falling asleep. "Restless legs" are a symptom: the sleep specialist makes the diagnosis after interviewing the patient, and polysomnography is not generally performed. Most patients with RLS also have periodic limb movement disorder. About 10 percent of the population suffers from RLS, which often runs in families. Medications are generally used to treat RLS.
Periodic Limb Movement Disorder
Periodic limb movement disorder (PLMD) is not just a symptom but is an electromyographic abnormality occurring in sleep. It is defined as the occurrence of periodic episodes of repetitive and highly stereotyped leg jerks occurring during sleep. Periodic limb movement disorder occurs primarily in the legs and may cause difficulty maintaining sleep. About 80 percent of patients with RLS demonstrate PLMD on PSG testing; on the other hand, among patients with PLMD on polysomnography, only about 30 percent complain of RLS. The number of periodic limb movements varies greatly from night to night. Both PLMD and RLS may lead to significant sleep disturbances and sleep fragmentation, and often result in daytime sleepiness or insomnia.
Bruxism
Bruxism is involuntary tooth grinding or jaw clenching during sleep and occurs in about 10 percent of people. It is more common in children than adults. Bruxism may be diagnosed during polysomnography by the repetitive EMG artifact observed on the chin muscle channel or on channels referenced to the ear.