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Seizures and Status Epilepticus
Seizures are frequently encountered in both the community and hospital setting. Epidemiologic studies in the United States have shown that 11% of the general population will have a seizure at some point in their life. Of these seizure patients, there is an estimated 1 million hospital visits due to seizures per year. The International League Against Epilepsy (ILAE) defines seizures as transient clinical events due to abnormally excessive or synchronous neuronal activity in the brain. These can manifest in a wide array of symptoms ranging from obvious convulsive activity to more subtle signs of twitching or altered mental status.
A failure to stop isolated seizures may lead to status epilepticus (SE). Its incidence has seen an increase in recent years with 5 to 30 cases per 100,000. SE is defined as convulsions lasting more than 5 minutes or two or more convulsions in a 5-minute interval without a return to preconvulsive neurologic baseline. Historically, SE had been defined as continuous convulsive seizure activity lasting greater than 30 minutes without complete recovery. However, the minimum time elapsed to qualify for SE was drastically shortened to 5 minutes based on the observation that convulsive seizures rarely last for more than a few minutes. Furthermore, seizures that are of longer duration typically do not stop spontaneously. Animal studies and human data have demonstrated irreversible brain injury can occur as early as 5 minutes of ongoing seizure activity. Delaying effective recognition and treatment of SE dramatically increases the patient’s morbidity and mortality. Thus, SE constitutes a neurologic emergency requiring prompt and decisive intervention.
CAUSES OF SEIZURES
It is important to identify any underlying cause for seizures, as management will be tailored to reverse these factors if possible (Table 6.1
). In adults without a history of prior seizures, stroke is the most frequent underlying etiology of seizures. The most common cause of SE is a history of epilepsy. Frequent precipitating factors in these patients include medication noncompliance, low antiepileptic drug (AED) levels, and recent changes in AEDs. Other seizures due to underlying metabolic derangements (hypoglycemia, hyponatremia) can be commonly seen but will be difficult to control with AED agents alone. Subsequently, timely investigation into the underlying cause of the seizure will need to be implemented in the management of acute seizures. Many of these provoking factors may be elicited from the patient’s history or exam as discussed previously; however, laboratory and imaging workup can further elucidate these factors. See “Initial Workup”
section for recommended testing.
TABLE 6.1 Etiology of Seizures
Stroke: ischemic or hemorrhagic
Metabolic derangement: hypoglycemia, electrolyte abnormalities, renal failure
Infection: CNS infection, sepsis
Drugs: AED noncompliance, withdrawal from alcohol, opiates, benzodiazepines, drug toxicity
Hypertensive encephalopathy (PRES)
Epilepsy with breakthrough seizures
Mass lesion: tumor, vascular malformations
Prior cortical CNS lesion: stroke, abscess, dysplasia
CNS, central nervous system; AED, antiepileptic drug; PRES, posterior reversible encephalopathy syndrome.
Adapted from Brophy GM, Bell R, Claassen J, et al. Guidelines for the evaluation and management of status epilepticus. Neurocrit Care. 2012;17(1):3-23.
Emergency EEG is indicated for patients who present with SE who fail to awaken after cessation of convulsive seizures.
Nonconvulsive seizures occur in up to 40% of patients who fail to awaken after convulsive seizures. This can cause further depression of level of consciousness and increase resistance to antiepileptic therapy if not controlled. Affected patients will not exhibit obvious physical signs of seizures, but electrographic seizure activity will be detected on EEG. As a result, the clinician must be wary of the possibility of nonconvulsive status epilepticus (NCSE) if the patient does not awaken after cessation of seizure activity or displays subtle symptoms of continuing seizures. Please see Chapter 58
for further details on seizure semiology, localizing signs, and seizure syndromes.
TABLE 6.3 Focused History: Questions to Ask in the Patient with Seizure
What symptoms were seen?
Hemibody versus generalized activity
What time was patient last seen normal?
How long did the activity last?
Did the patient return to baseline at any point?
Recent illness or fever
Prior medical history (e.g., stroke, brain tumor, brain infection)
TABLE 6.4 Drugs that Lower the Seizure Threshold
Analgesics: narcotics (tramadol, fentanyl, meperidine)
Antibiotics: penicillins, imipenem, cephalosporins, isoniazid, metronidazole
Antidepressants: bupropion, tricyclics
Antipsychotics: clozapine, phenothiazine
Chemotherapy: etoposide, cisplatinum
EMERGENT TREATMENT OF STATUS EPILEPTICUS
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