Acute seizures are common and are defined as a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.1 Intrinsically, the brain has mechanisms in place to terminate excessive electrical activity. The mean duration of a secondarily generalized tonic-clonic (GTC) seizure is 53 to 62 seconds, and rarely lasts longer than 2 minutes.2,3 However, some seizures do not stop and progress to status epilepticus (SE), which may be convulsive (CSE), with clinically apparent motor (clonic) rhythmic jerking and/or (tonic) stiffening, or nonconvulsive (NCSE), with seizure activity on electroencephalography (EEG), and subtle or no obvious clinical signs. Status epilepticus is a neurological emergency often requiring management in the intensive care unit (ICU) for causes or complications of SE, or both.
DEFINITION AND CLASSIFICATIONS
In 2015, the International League Against Epilepsy (ILAE) proposed a conceptual definition that applies to all types of SE: (1) SE starts as a condition resulting from failure of seizure-termination mechanisms or the initiation of pathological mechanisms that likely lead to continuous seizure activity, and (2) SE creates long-term consequences that begin to occur after the onset of SE, including neuronal death, neuronal injury, and alteration of neuronal networks. This definition hinges on the identification of the semiology of SE: the clinical manifestations of seizure activity (Table 16-1). Specifically for generalized CSE, criterion 1 is defined when seizures last longer than 5 minutes and criterion 2 occurs at the point that long-term consequences begin to appear, around 30 minutes.1 Convulsive SE is also defined as recurrent seizures between which there is incomplete recovery of consciousness.4
TABLE 16-1Semiologic Classification of Status Epilepticus ||Download (.pdf) TABLE 16-1Semiologic Classification of Status Epilepticus
|With Prominent Motor Symptoms ||Without Prominent Motor Symptoms |
Nonconvulsive SE (NCSE)
NCSE with coma
NCSE without coma
Generalized: typical absence, atypical absence, myoclonic absence
Autonomic (unknown whether focal or generalized phenomenon): episodic/paroxysmal desaturations, apnea, heart range and blood pressure changes, nausea/emesis
The point at which focal seizures or nonconvulsive seizures become SE (criterion 1) ...