Periodic limb movements and restless legs syndrome are both relatively common conditions. The incidence of restless legs syndrome is between 2.5% and 15%. Periodic limb movements occur in about 5% of young adults, however the prevalence may be as high as 44% in patients over age 64. These two disorders often occur together and have many characteristics in common, thus are discussed together.
Periodic limb movements consist of repetitive cycles of rhythmic movements, usually occurring in one or both legs but sometimes involving the arms. Patients are unaware of the movements but may report frequent awakenings. The history from a bed partner may be of jerking movements in sleep, therefore potentially resulting in confusion with epilepsy. On closer questioning, however, the movements are not clonic, are typically limited to a single limb, and occur many times during the night at regular intervals. Most commonly, they occur in clusters every 5-90 seconds with each movement lasting 0.5 to 5 seconds.
Restless legs syndrome is usually characterized by an itching or burning sensation in the legs which occurs when the patient is relaxed, particularly when trying to go to sleep. This is followed by movement of the legs with relief of the sensation. The movement can be suppressed voluntarily however typically the urge to move becomes overwhelming. Many patients need to actually walk to stop the sensation. As opposed to periodic limb movements, restless legs syndrome becomes manifest during wakefulness or drowsiness as opposed to sleep. The result, however, is that the patient is unable to sleep and it results in daytime drowsiness. Similar to periodic limb movements, however, a description of irresistible shaking of the legs could be confused with epilepsy; a major difference is that restless legs syndrome can be suppressed voluntarily while an epileptic seizure cannot be suppressed. Kidney problems are an important cause of restless legs syndrome, and prevalence may be as high as 40%. Other important associated conditions include iron deficiency anemia, pregnancy, peripheral neuropathy, and drugs (neuroleptics, caffeine).
Treatment of both conditions begins with a search for underlying cause. Either condition can be asymptomatic, but if associated drowsiness requires pharmacological treatment, dopaminergic agents (carbidopa/levodopa, bromocriptine), benzodiazepines (clonazepam), opioids (codeine), and carbamazepine may be recommended by a sleep specialist.