Epidemiology and evidence for morbidity of nonconvulsive status epilepticus

Convulsive status epilepticus (SE) is convincingly related to serious morbidity and mortality and well recognized as a medical emergency, but prompt diagnosis and treatment of patients with nonconvulsive status epilepticus (NCSE) is often not emphasized because its consequences are thought to be benign. Nonconvulsive status epilepticus has been considered a relatively benign entity because it does not produce the adverse systemic consequences of convulsive status epilepticus, such as hyperthermia, acidosis, hyperkalemia, pulmonary compromise, or cardiovascular collapse. However, recent reports indicate that NCSE is not so benign. There are two major forms of NCSE, absence status epilepticus and complex partial status epilepticus. Typical absence status epilepticus does not appear to have very serious consequences and may be a type of "inhibitory" seizure, but complex partial status epilepticus has been associated with serious morbidity and mortality. Despite not causing the systemic physiologic or metabolic derangements seen with convulsive SE, complex partial status epilepticus is still associated with the two other major factors correlated with poor outcomes in convulsive SE: 1) neuronal damage from abnormal electrical activity and 2) the interaction of acute neurologic disorders, such as stroke, that may precipitate SE. Other similar epileptiform encephalopathies such as "subclinical," "electroencephalographic," "nontonic-clonic," and "subtle" SE have not been as well studied as NCSE but pose similar issues. Early diagnosis and aggressive intervention have proven the best means of averting adverse outcomes in patients with convulsive SE. The diagnosis and treatment of NCSE, particularly complex partial status epilepticus, merit similar emphasis and attention.