Myoclonic status epilepticus: a clinical and electroencephalographic study.

We reviewed the clinical features and ictal EEGs in 23 adults with myoclonic status epilepticus (MSE). Anoxic encephalopathy was the most common cause of MSE, occurring in 15 patients; 8 developed MSE within 14 hours following the anoxic insult. Metabolic encephalopathies were present in 4 patients, while 2 had degenerative CNS disorders. In 2 patients with generalized epilepsy, MSE developed during a medication change. Five types of EEG patterns were associated with MSE. Generalized periodic complexes (usually spikes, polyspikes, or sharp waves), often with attenuation of background activity between complexes (11 patients) or a burst-suppression pattern (4 patients), were the most common types. Outcome was poor: 20 patients died without regaining consciousness, while 1 remains in a vegetative state. The 2 patients with generalized epilepsy, both of whom were conscious during MSE, survived without sequelae.