Status epilepticus is a continuous seizure lasting more than 5 minutes, or a series of seizures without recovery of consciousness in between. After this period of time, seizures are unlikely to spontaneously remit without treatment.

Status epilepticus can occur in patients with known epilepsy, but it may also be the presenting sign for a number of illnesses. The most common cause of status epilepticus is a patient's anti-epileptic drugs being at a subtherapeutic level. Other common causes include central nervous system infection, intracranial hemorrhage, stroke, anoxic brain injury, congenital malformations, metabolic or electrolyte abnormality, drug intoxication, and alcohol withdrawal.

Status epilepticus most commonly has a tonic-clonic presentation that involves rhythmic flexion and extension of the extremities with loss of consciousness (generalized status epilepticus). Patients may, however, present with altered consciousness lacking any rhythmic movements. This is termed nonconvulsive status epilepticus. Nonconvulsive status epilepticus can also evolve out of treated convulsive status epilepticus. Simple partial status epilepticus (SPSE) is a focal seizure without impairment of consciousness lasting longer than 5 minutes. Its clinical presentation can vary dramatically depending on the localization of the seizure activity. Seizures may present only with focal motor abnormalities, sometimes called epilepsy partialis continua. Simple partial status epilepticus can also present with a purely sensory phenomenology. Patients report paresthesias, olfactory or visual hallucinations, or numbness.

Generalized status epilepticus can be fatal, and immediate evaluation and treatment is essential.