31 Evaluating and Treating Status Epilepticus

Jeffrey Bolton¹ and Howard P. Goodkin²

¹ Department of Neurology, Boston Children’s Hospital Division of Epilepsy, Harvard Medical School, Boston, MA, USA
² Division of Pediatric Neurology, Department of Neurology, University of Virginia, Charlottesville, VA, USA

Status epilepticus (SE) is the term applied to a prolonged, self-sustaining seizure or frequent, recurrent seizures that occur without a return to baseline. SE does not represent a single disease, nor does it represent a single seizure type. Although frequently the term “status” is used as a shorthand for an episode of generalized convulsive SE (e.g., tonic–clonic SE), the clinical manifestations of SE are broad, ranging from overt generalized or focal convulsive SE to nonconvulsive forms characterized by an alteration of consciousness (e.g., complex partial SE) to complete loss of consciousness (electrographic SE in the comatose patient in the ICU setting) in the absence of motor symptoms.

Given the multiple different clinical manifestations, it has proved hard to develop a universally accepted definition. Epidemiological definitions typically distinguish SE from self-limited seizures based on time durations of 30–60 min. Yet, it is neither practical nor appropriate to wait for 30 min or longer to initiate care in some SE types; therefore, a current operational definition for generalized convulsive SE has defined the duration as 5 min.

SCIENCE REVISITED

Studies investigating SE pathogenesis have demonstrated that SE is a dynamic, evolving process during which there are ongoing changes in the surface expression of several molecules including GABA_A receptors, NMDA receptors, AMPA receptors, HCN channels, and potassium channels. These changes may account, in part, for the self-sustaining nature of SE and the inverse correlation between seizure duration and the effectiveness of current SE first-line therapies.

Epidemiology and etiology

Status epilepticus is common, with an estimated annual incidence ranging from 15 to 50 episodes per 100,000 persons per year. Worldwide, these values translate to a minimum of 1 million episodes of SE per year.

Status epilepticus is most common at the extremes of life. In the classic prospective, population-based SE epidemiological study performed in Richmond, VA, the incidence was nearly 150 per 100,000 persons in children less than 1 year of age. The incidence dropped to less than 25 per 100,000 persons by 5 years of age until it increased again to greater than 50 per 100,000 persons after 40 years of age. This bimodal distribution has been observed across multiple prospective studies.

As noted earlier, SE is not a single disease but a symptom that can be the result of either a primary central nervous system disorder or a secondary symptom from a systemic disorder. It occurs in both those with and those without a history of preexisting epilepsy. The range of precipitants is wide and varies by age. Common etiologies include cerebrovascular disease and anoxia, metabolic disturbances, trauma, tumor, fever, infection, and in those with epilepsy, noncompliance with antiepileptic medication or medication changes. In the Richmond study that included both children and adults, acute symptomatic causes accounted for 52% of the episodes, remote symptomatic causes accounted for 39%, and idiopathic/cryptogenic/unknown causes accounted for 5%. In the prospective North London study that included only children, acute symptomatic causes (including febrile seizures) accounted for 49%, remote symptomatic causes accounted for 16%, remote symptomatic causes with an acute precipitant accounted for 16%, and idiopathic/cryptogenic/unknown causes accounted for 19%.

Convulsive status epilepticus

Attempts to develop a single classification system for the many seizure types of SE are ongoing. Currently, a simplified semiologically based system that divides SE broadly into convulsive and nonconvulsive forms is frequently informally employed.

Generalized convulsive SE is characterized by continuous or repeated tonic and/or clonic motor movements associated with loss of consciousness accompanied by an ictal electroencephalogram (EEG) pattern. Generalized convulsive SE may follow a dynamic progression of isolated recurrent seizures that wax and wane, ultimately evolving into a single continuous seizure. If seizures are refractory to treatment or left untreated, electromechanical dissociation may occur in which the motor component becomes more subtle, consisting of only minor jerking or twitching, while the EEG reveals persistence of a continuous or possibly periodic (i.e., periodic epileptiform discharges [PEDs]) ictal EEG pattern.

Focal motor SE without impairment of consciousness (i.e., epilepsia partialis continua [EPC]) can last for prolonged periods of time and is often refractory to medication. The motor manifestations of EPC are often clonic movements restricted to a single body region, commonly in the upper extremities. The differential diagnosis for this form of SE includes cerebral neoplasia (primary or metastatic), cortical dysplasia, vascular lesion, focal infection, and inflammatory causes such as Rasmussen’s syndrome.

Nonconvulsive status epilepticus

The term nonconvulsive SE incorporates a number of different clinical situations. As described previously, nonconvulsive SE may represent the end stages of generalized convulsive SE. In addition, nonconvulsive SE also includes focal SE with impairment of consciousness (i.e., complex partial SE), absence SE, as well as the increasingly recognized state of unresponsiveness in the ICU associated with an ictal EEG pattern on bedside EEG monitoring. This condition is discussed in Chapter 32.

Complex partial SE should be considered in a patient with a persistent altered mental status ranging from slightly confused to nearly comatose. Motor symptoms are minor and typically manifest as automatisms. Patients in complex partial SE have been described as functioning in an “epileptic twilight state” or as the “wandering confused.” They tend to cycle between periods of relative lucidness and episodes of motionless staring or complete unresponsiveness.

The term spike–wave stupor refers to a prolonged absence seizure causing the patient to present in a confusional state. Unlike complex partial SE, absence SE does not have cycling between responsive and unresponsive states, but instead tends to consist of mild persistently slowed mentation or lethargy. Although upon initial presentation absence SE may be difficult to differentiate from complex partial SE, an EEG will provide prompt clarification, demonstrating prolonged, often continuous, generalized 3-Hz spike-and-wave discharges. Subtle motor symptoms may be present, including myoclonic twitches of the eyelids or facial muscles. Absence SE occurs in children with primary generalized epilepsies. In adults, it may occur de novo (de novo absence in adults) as well as in the setting of benzodiazepine withdrawal or a prior history of absence seizures as a child.

There can also be focal forms of nonconvulsive SE without impairment of consciousness. These are characterized by a prolonged aura (aura continua) of sensory, special sensory, autonomic, or cognitive symptoms. The symptoms (e.g., dysesthesia, visual changes, fear) are dependent on cortical localization and can wax and wane over the duration of the prolonged seizure.

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