Generalized convulsive status epilepticus (GCSE) is the most dramatic, most dangerous, and best-studied type of SE. It is potentially life-threatening but also treatable. A plan for medical management and pharmacotherapy is crucial. The clinician needs to understand its etiology, electrophysiology, pathophysiology, course, and consequences.
Convulsive SE is readily recognizable. It may start with simple or complex partial seizures but often begins with a generalized convulsion. Convulsions recur, most lasting only a minute or so, along with intervals of persistent unresponsiveness. Each convulsion may begin with several seconds of a tonic phase with tensing of extensor muscles and forced expiration, followed by a clonic phase with gradually slowing clonic movements. Both phases usually involve bilateral and symmetric movements, although there may be a focal onset with head or eye deviation, even without unilateral limb movement. Consciousness is impaired, at least from the time of tonic seizures.
Less often, convulsions are continuous. In this case clonic movements eventually diminish, often being replaced by repetitive jerking movements of the eyes, eyelids, or facial muscles alone or sometimes with intermittent limb jerking. These signs constitute "subtle" SE and imply continuing epileptic brain activity with a "decoupling" of electrical and motor systems.
The incidence of convulsive SE is usually estimated to be about 60,000 cases each year in the United States (probably over half of them in children), but population-based surveys suggest that it may occur several times as often. The incidence of other forms of SE is less well documented.
Convulsive SE is not a disease itself but, rather, a serious manifestation of some underlying disorder. The following list shows etiologies and percentages of patients affected; these figures are obtained from a summary of several studies of adult patients.
|Cerebrovascular (stroke, anoxia, hemorrhage)||22|
|Metabolic: acute encephalopathy (e.g., hypoglycemia, systemic infection)||22|
These percentages total more than 100% because of multiple causes. For instance, a patient with a congenital lesion and chronic epilepsy may experience anticonvulsant withdrawal or infection.
The causes of convulsive SE may vary tremendously in different populations. In urban hospitals, for example, SE is more often related to alcohol and drugs. The causes or precipitants of convulsive SE are also different in patients with known epilepsy than in those presenting with acute, new illness. Congenital abnormalities and infection increase in importance in children.
Often, there is an interaction between acute systemic illness and earlier neurologic disease, including epilepsy and other earlier neurologic insults. A history of epilepsy is often assumed, but in actuality about two-thirds of SE cases occur in patients who have not had prior seizures.
About 1% of patients with epilepsy will have an episode of SE in a given year. Anticonvulsant withdrawal is often assumed in patients with epilepsy, although this may be less frequent than presumed. Anticonvulsant changes initiated by physicians may cause withdrawal seizures as often as patient noncompliance. Adding new anticonvulsants may alter metabolism and lead to subtherapeutic or toxic levels of prior medications.
Infections may have a role in epileptogenicity, but several antibiotics also can precipitate seizures and alter anticonvulsant metabolism.
The epidemiology of convulsive SE has several clinical implications:
Reviewed and revised January 2004 by Thaddeus Walczak, MD, MINCEP® Epilepsy Care, Minneapolis, MN
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