Simple seizures, motor seizures, and somatosensory seizures are classified as what type of seizure?

Status epilepticus (SE) is a common, life-threatening neurologic disorder. It is essentially an acute, prolonged epileptic crisis. [2]

Etiologically, SE can be imperfectly divided into 3 groups. SE can represent an exacerbation of a pre-existing seizure disorder, the initial manifestation of a seizure disorder, or an insult other than a seizure disorder (see Etiology). In patients with known epilepsy, the most common cause is a change in medication.

Recognition of SE may be easy or difficult. SE in the patient with sequential, generalized major motor convulsions is obvious; the patient with nonconvulsive or subtle SE presents a diagnostic dilemma (see Differentials).

Aggressive treatment is necessary. Maintenance of vital signs, including respiratory function, is of major importance. Early treatment measures are performed in concert with diagnostic studies (see Treatment). [9, 10] Treatment guidelines for status epilepticus have been proposed [11]  and have been confirmed in updated reviews. However, there is more to learn about the anticonvulsant of choice in cases of prolonged or refractory SE.

Go to Epilepsy and Seizures for an overview of this topic. Also see Pediatric Status Epilepticus.

The first description of SE in the medical literature was in a Babylonian text from the first millennium BC. The author recognized the severity of the condition: "If an epilepsy demon falls many times upon him on a given day, he seven times punishes him and possesses him, his life will be spared. If he falls upon him eight times, his life may not be spared." [12]

Wolf et al described a case of probable 3-day absence stupor documented in Austria in 1501. [13] Several descendants of the affected person in this historical case have been shown to have a primary idiopathic epileptic syndrome.

In early studies, SE was defined by its duration—that is, as continuous seizures occurring for longer than 1 hour. Clinical and animal experiences later showed that pathologic changes and prognostic implications occurred when SE persisted for 30 minutes. Therefore, the time for the definition was shortened.

The working group on SE of the Epilepsy Foundation (formerly the Epilepsy Foundation of America) formulated the current definition: "More than 30 minutes of continuous seizure activity or two or more sequential seizures without full recovery of consciousness between seizures." [14]

Many believe that a shorter period of seizure activity causes neuronal injury and that seizure self-termination is unlikely after 5 minutes. [15] Consequently, Lowenstein and others have suggested a duration of longer than 5 minutes as part of the a criterion for SE, if the seizure type is one in which typical generalized convulsive seizures resolve spontaneously after 3-5 minutes. [16] The Epilepsy Foundation working group recommended that emergency department physicians treat seizures as SE if seizure activity has continued for more than 10 minutes. [14]

The term status epilepticus may be used to describe continuing seizure of any type.

The predominant type of seizure further refines the definition of SE, and several classification schemes have been proposed.

Categorization of SE cases is no simple matter because they often exhibit characteristics of both focal and generalized processes. Considerable literature has been devoted to this question over the last 30 years, beginning with Geier et al in 1976, [17] Ellis and Lee in 1978, [18] and Niedermeyer et al in 1979. [19]

Several investigators have suggested that the bulk of these indeterminate examples are instances of focal onset episodes of status that have secondarily generalized, in the same manner as many focal onset seizures. EEGs of patients with these conditions fail to capture the onset of status; therefore, this critical element is lost.

Some of these instances are characterized by diffuse, slow (< 3 Hz) spike-and-wave activity, albeit with focal predominance. In many instances, interictal recordings demonstrate focal discharges that further implicate a focal process. Whether such cases are best grouped with focal status remains controversial.

Luders and Rona [1] have suggested a detailed semiologic classification along 3 axes: (1) the type of brain function predominantly compromised, (2) the body part involved, and (3) The evolution over time. Celesia [20] and Treiman [21] proposed simpler schemes, which are more useful than other systems for emergency treatment decisions.

The Treiman classification is as follows:

• Generalized convulsive SE

• Nonconvulsive SE (including absence SE and complex partial SE)

Generalized convulsive SE is the most frequent and potentially dangerous type of SE. Generalized refers to the abnormal excessive cortical electrical activity, while convulsive refers to the motor activity of a seizure.

Subtle SE consists of electrical seizure activity in the brain that endures when the associated motor responses are fragmentary or even absent.

The terminology is confusing, since subtle SE is sometimes designated a type of nonconvulsive SE (NCSE). Although subtle SE is, by definition, nonconvulsive, it should be distinguished from other NCSE. Subtle SE is considered the most severe clinical stage of generalized convulsive SE and patients with subtle SE, in contrast to that of those with NCSE, have a dismal prognosis.

Nonconvulsive SE is divided into 2 categories: absence SE and complex partial SE. Differentiating these subtypes is important, since they indicate major differences in treatment, etiology, and prognosis.

In one review, [10] NCSE has been further subdivided according to the age of occurrence, as follows:

• In both childhood and adult life

Several epileptic syndromes, such as electrical status epilepticus in slow-wave sleep (ESES), would be classified under the "NCSE only in childhood" category.

On clinical presentation, a clear change in the level of consciousness is observed in patients with absence SE. Most patients are not comatose but are lethargic and confused, with decreased spontaneity and slow speech. Absence SE is also known as absence stupor because of the apparent state of low alertness.

The ictal electroencephalograph (EEG) during typical absence SE demonstrates generalized spike and wave discharges. The frequency may be slower than 3 Hz, and the waveforms (though bilaterally synchronous) are often irregular, poorly formed, and discontinuous, especially in the late stages. In adults and in some children, the apparently bisynchronous EEG discharges may represent complex partial SE as opposed to true absence SE.

About 2.6% of patients with absence seizures have had an episode of absence SE earlier in their lives. [22] Approximately 10% of adults with childhood-onset absence seizures experience absence SE. [23] About 75% of all cases of absence SE occur before the age of 20 years. When it occurs in adults, the patients are often elderly. The mean age of onset of absence SE in adults is 51 years.

Typical absence SE that occurs in children or adolescents who have primary or idiopathic generalized epilepsy (which includes absence seizures) readily responds to treatment. In contrast, absence SE in the symptomatic, primary generalized epilepsies (eg, Lennox-Gastaut syndrome) is often more difficult to control.

Four issues should be considered in the differential diagnoses of absence SE. First, complex partial SE usually manifests with recurring cycles of 2 separate phases: ictal and interictal. In contrast, absence SE usually occurs as 1 continuous episode of variable intensity.

Second, stereotyped automatisms can be seen in both complex partial and absence SE, though they tend to be richer in complex partial SE than in absence SE. Anxiety, aggression, fear, and irritability may be most common in complex partial SE, but they can be seen in both types.

Third, EEG is the best way to differentiate absence SE from complex partial SE.

Fourth, other possibilities include a postictal state and encephalopathies from toxic-metabolic causes, drugs, trauma, or infection. Psychiatric causes should be considered.

No deaths or long-term morbidity due to typical absence SE have been reported. Whether absence SE in children with developmental dementia and myoclonic/astatic epilepsy is injurious to the brain is controversial. Differentiating absence SE from other causes is important because many mimics of absence SE can lead to irreversible neuronal damage if they are not aggressively treated.

Complex partial SE is rare. Although many cases of prolonged complex partial SE without long-term neurologic sequelae have been described, negative outcomes can occur. No criteria for differentiating the cases associated with a poor outcome are known.

Complex partial SE that arises in the limbic cortex (eg, mesial temporal lobe) causes signs and symptoms such as staring, unresponsiveness, automatisms, atypical anxiety, rising abdominal symptoms, déjà vu, or more profound stupor. Complex partial SE of frontal-lobe origin may produce clinical symptoms indistinguishable from cases of temporal-lobe origin.

While isolated complex partial seizures usually originate in the temporal lobe, complex partial SE usually has an extratemporal focus. Shorvon believes that at least 15% of patients with complex partial epilepsy have a history of nonconvulsive SE. [24]

By definition, simple partial SE consists of seizures that are localized to a discrete area of cerebral cortex and produce no alteration in consciousness. Because this form of epilepsy is rare, no good studies have been done to determine its incidence.

Focal SE can arise in any region of the cortex. When motor cortex is affected, the condition is termed epilepsia partialis continua (EPC), which characteristically involves repetitive, often rhythmic, unilateral focal twitching of the limbs and/or face, usually with preservation of consciousness. This sparing of consciousness subcategorizes EPC as a form of simple partial SE.

Other regions of cortex similarly may generate focal SE. These cases are characterized by predictable phenotypes depending on the function of the particular region involved. For example, episodes of focal SE involving primary sensory cortex are expected to be associated with focal sensory symptoms, and occipital focal SE causes focal visual symptoms (eg, flashing spots of light, colorful visual hallucinations). Focal SE of language cortex typically causes aphasia, termed ictal aphasia.

Diagnosis is primarily based on clinical findings. Because of the relatively small area of cerebral cortical involvement, results of conventional scalp EEG are frequently uncharacteristic of the clinical ictal activity, or they may be normal.

In contrast to convulsive SE, simple partial SE is not associated with high rates of morbidity or mortality. Outcomes seem to be related to the underlying etiology, the duration of the SE, the age of the patient, and the medical complications, as in convulsive SE.

Treatment involves the same drugs and general pharmacologic principles as those used for convulsive SE. However, the relatively low morbidity and mortality rates suggest that aggressive treatment might not be needed. For example, if first-line drugs are ineffective, the clinician may elect not to use a general anesthetic agent to stop simple partial SE.