Nocturnal myoclonus involves repetitive movements of the legs during sleep or even wakefulness. It is sometimes confused with a seizure.
How Is Nocturnal Myoclonus Different from Seizures?
Although the cause is not clear, nocturnal myoclonus may involve problems with a neurotransmitter called dopamine -- this is unlike seizures, which involve electrical changes in the brain. Myoclonus also may result as a side effect to some drugs, including levodopa, cyclic antidepressants, and bismuth salts. The condition often improves after a patient stops taking the drug causing the problem. If you suspect this is your problem, talk to your doctor before abruptly stopping any medication, however.
This condition also sometimes affects infants, known as benign neonatal sleep myoclonus. The jerking movements occur during sleep and abruptly stop when the baby is awakened. It generally goes away with age. Importantly, there are no electrical changes on EEG indicating a seizure.
Other conditions with slightly different symptoms also may affect the legs and disrupt sleep. These include restless legs syndrome, periodic limb movements of sleep, night starts, and nocturnal leg cramps. They may need further evaluation and treatment (except for night starts).
Can Nocturnal Myoclonus Be Treated?
If nocturnal myoclonus is disruptive to sleep, it may be treated with tetrabenazine, a drug often used to treat movement disorders such as Huntington’s disease. In one study, the condition was significantly improved over a period of five years using this drug, with drowsiness as the most significant side effect. In most cases, however, treatment is not necessary if sleep is relatively normal.
Sources:
Jimenez-Jimenez, F. et al. “Drug-induced myoclonus: frequency, mechanisms and management.” CNS Drugs. 2004; 18:93.
Kenney, C. et al. “Long-term tolerability of tetrabenazine in the treatment of hyperkinetic movement disorders.” Mov Disord. 2007; 22:193.
Sheon, R. “Nocturnal leg cramps, night starts, and nocturnal myoclonus.” UpToDate. Accessed November 2, 2009.
Staedt, J. et al. “Nocturnal myoclonus syndrome (periodic movements in sleep) related to central dopamine D2-receptor alteration.” Eur Arch Psychiatry Clin Neurosci. 1995; 245:8.
Turanli, G. et al. “Benign neonatal sleep myoclonus mimicking status epilepticus.” J Child Neurol. 2004; 19:62.
