Myoclonus and the electroencephalogram, a review.

Myoclonus is a phenomenon which cuts through a considerable number of neurological conditions. It occurs in a variety of epileptic conditions (Primary generalized epilepsy, hypsarrhythmia, Lennox-Gastaut syndrome, also known as "petit mal variant"), in inborn errors of metabolism (Tay-Sachs disease, forms of ceroid lipofuscinosis), in neurobiochemically still poorly understood forms of degenerative processes such as Essential hereditary myoclonus epilepsy (Lafora-Unverricht-Lundborg), in benign heredo-degenerative disorders (Hartung's syndrome), in CNS infections (SSPE, Jakob-Creutzfeldt disease), in metabolic encephalopathies (renal failure, hypoglycemia), in CNS poisoning, in acute cerebral anoxia and in post-anoxic states. The EEG plays a crucial role in the differential diagnosis of these conditions by the demonstration of a) presence or absence of typical inter-ictal abnormalities, and b) various correlates of the myoclonic ictal event.