Serotonergic mechanisms in myoclonus.

Post-hypoxic intention myoclonus is a specific myoclonic syndrome in which central serotonergic tone may be deficient. Tryptophan and 5-hydroxytryptophan administration to patients with post-hypoxic intention myoclonus increases pre-existing low levels of 5-hydroxyindoleacetic acid levels in the cerebrospinal bluid, and also suppresses myoclonus. Serotonin precursor administration does not help all patients with myoclonus and may actually worsen some myoclonic syndromes, including those secondary to lipid storage diseases. Treatments that alter serotonin metabolism can also produce myoclonus in experimental animals but their relevance to myoclonic syndromes in humans remains uncertain.