Key Clinical Questions
How can clinicians distinguish between seizures, syncopal events, and other seizure mimics?
What historical features are helpful? What diagnostic tests are appropriate?
Which patients with new-onset seizures require an antiepileptic drug?
How should patients with status epilepticus be managed?
A seizure is defined as a sudden attack of involuntary behavior or sensory experiences resulting from abnormal cortical neuronal activity. About 10% of the population of the United States will experience a seizure at some point during their lifetime, and seizure accounts for 1% to 2% of emergency room visits in the United States each year. Epilepsy is a disease of the brain defined by any of the following conditions: (1) at least two unprovoked (or reflex) seizures occurring greater than 24 hours apart; (2) one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years; (3) diagnosis of an epilepsy syndrome. Epilepsy is the fourth most common neurological disorder in the United States, and has a lifetime prevalence of 3%. The World Health Organization (WHO) reports that in primary care settings worldwide, epilepsy is the second most common neurologic condition, after headache.
TRIAGE AND HOSPITAL ADMISSION
Epilepsy and seizures are also common in the inpatient setting. In a large multicenter study in both community and academic hospital emergency departments, 1.2% of 31,508 patient visits were related to seizures. Overall, 27% of these patients were admitted. Of those patients suspected of having new-onset seizures, 63% were admitted. Reasons for admission of patients with seizures include diagnostic evaluation, uncontrolled seizures, toxicity from antiepileptic drugs (AEDs), and injuries sustained during a seizure.
CLASSIFICATION AND CLINICAL FINDINGS
Seizures are classified into two broad categories, based on whether the primary onset is focal or generalized (Table 211-1). The terminology has recently been updated, so both the updated and the former terms will be presented. Focal seizures (formerly known as partial seizures) start with abnormal neuronal discharges from a seizure focus limited to one cerebral hemisphere. The abnormal electrical activity may remain limited to that hemisphere, or can generalize to involve both hemispheres. Focal seizures are further subdivided based on whether there is an associated change in mental status or awareness. During a focal seizure without dyscognitive features (previously called a simple partial seizure), the patient remains awake and aware throughout and does not experience a change in cognition. In contrast, a focal seizure with dyscognitive features (previously termed a complex partial seizure) arises from abnormal electrical activity in one cerebral hemisphere and is accompanied by alteration in awareness or consciousness during the event. This change in consciousness may manifest as inattentiveness, blank staring, or unresponsiveness to questions or stimulus, but unless the seizure secondarily generalizes, it does not involve loss of consciousness.