Approximately 5% of children will have at least one seizure before the age of 20 years.¹ A seizure is the manifestation of abnormally synchronized electrical activity in the brain. The initial approach to a patient with a seizure should focus on stabilizing the patient and evaluating for potentially reversible seizure causes. While most unprovoked seizures are brief and resolve spontaneously, seizures secondary to metabolic disturbances, infections, or intracranial hemorrhage may be more prolonged. Timely evaluation and treatment are essential in preventing or minimizing the complications of a prolonged seizure, including hypoventilation, tissue hypoxia, and cerebral edema.

Most children who experience a single seizure, which is often provoked by fever or acute illness, do not go on to develop epilepsy. Epilepsy is diagnosed by the presence of recurrent unprovoked seizures and has a prevalence in childhood of approximately 0.5%.²

CLINICAL PRESENTATION

The presentation and seizure semiology (symptoms during a seizure) depends on the region of brain involved as well as the underlying etiology. Epilepsy classification systems are clinically useful frameworks and provide diagnostic and therapeutic criteria.

Previous classification systems (e.g. the 1981 International Classification of Epileptic Seizures and the 1989 International Classification of Epilepsies, Epileptic Syndromes, and Related Disorders), although widely accepted, were based primarily on the phenomenology of the seizure and concepts that predate the era of neuroimaging, genetic technologies, and modern molecular biology. Since 2001, the International League Against Epilepsy (ILAE) has moved toward a classification that allows for neuroscientific advances to be incorporated into clinical practice.³ Additional revisions were made in 2006 and 2010.⁴

According to the 2010 ILAE revised terminology, seizures have been classified as either generalized or focal (Table 118-1). Generalized seizures are defined as originating anywhere within, and rapidly involving, bilateral hemispheres. They can be asymmetric. This produces a loss or impairment of consciousness and may produce tonic activity (stiffening), clonic activity (rhythmic jerking), tonic-clonic activity (stiffening followed by or alternating with rhythmic jerking), atonic activity (loss of tone), myoclonic activity (sudden contraction of muscles), or absence seizures (typically with staring, blinking, and automatisms). Focal seizures originate from networks limited to one hemisphere. Simple partial and complex partial terms, while still used in clinical practice, are being replaced by different focal seizure descriptors according to the degree of impairment during seizures (Table 118-2). For example, a focal seizure beginning in or rapidly spreading to the left motor strip (left frontal cortex) would likely involve clonic movements of the right arm, leg, or face without impairment of consciousness. A focal seizure arising from the temporal lobe might result in an abnormal psychic experience such as déjà vu. A focal seizure can spread to involve the entire cortex and produce generalized seizure activity.

The stereotypical presentations of focal and generalized seizures are as described earlier, but any change in consciousness or unexplained loss of consciousness can be due to electrical seizure activity without other outward signs. Therefore seizure—particularly nonconvulsive status epilepticus—must be included in the differential diagnosis of any patient with an altered mental status or altered level of consciousness.

The new classification also formalized the term electroclinical syndrome, which consists of clinical features, signs, and symptoms as well as electrographic features that define a distinctive clinical disorder (Table 118-3).

Status epilepticus, or a continuous seizure, is usually defined as a single clinical seizure lasting longer than 30 minutes or recurrent seizures over a period longer than 30 minutes without intervening return to baseline mental status.⁵

DIFFERENTIAL DIAGNOSIS

The differential diagnosis of seizure includes a variety of neurologic and non-neurologic conditions (Table 118-4). In a previously normal child, the evaluation of a first seizure should include a careful review of the event itself and its possible precipitating factors. In most cases, a description of the event by the parent or caretaker, or possibly from the child, must suffice in arriving at a working clinical diagnosis.

DIAGNOSIS AND EVALUATION

The causes of a new seizure in a previously healthy child or an increase in seizure frequency in a child with known seizures should always be investigated. Although an otherwise healthy child is unlikely to have an occult abnormality, children with known epilepsy may have an underlying infection, such as a urinary tract infection, or other systemic disturbance that tend to decrease the seizure threshold. Factors that can provoke seizures are listed in Table 118-5. The likelihood of each must be judged on the basis of the entire clinical picture. The same precipitating factors apply to children with epilepsy who are taking antiepileptic medication, along with the additional considerations listed in Table 118-6.

The pace and extent of the diagnostic evaluation depend on the clinical setting. A detailed history and physical examination—with immediate assessment of airway, breathing, circulation, and glucose, followed by a comprehensive general and neurologic examination—should guide the evaluation. Table 118-7 presents several approaches to the diagnostic evaluation of a child with seizures, based on the clinical history and state of the patient.

In a stable, well-appearing, otherwise healthy child who presents with a brief new-onset seizure, extensive laboratory evaluation is of little diagnostic value. In the emergency department, a typical evaluation includes measurement of glucose, serum electrolytes, and calcium. There is evidence that even this limited screen for abnormalities is not necessary in patients older than 6 months with no concern for dehydration or gastrointestinal losses who have returned to baseline mental status.⁶ The history and clinical judgment must be used to decide whether other tests, such as urine toxicology screening, are needed. A previously healthy child with a new unprovoked seizure should have neurologic follow-up within 1 to 2 weeks for a comprehensive evaluation, including an electroencephalogram (EEG). Outpatient magnetic resonance imaging (MRI) should be performed after a first-time seizure in most cases, including all children younger than 1 year of age and children with a history of focal seizures or convulsive seizures for which the onset may have been focal, even if not directly observed. In addition, children with an abnormal neurologic history or examination or with EEG abnormalities that do not fall into the category of a primary generalized or benign epilepsy syndrome (e.g. childhood absence epilepsy).⁶ Both EEG and MRI can be helpful in assessing the risk of seizure recurrence.

Ill-appearing children warrant a more extensive initial evaluation. In the presence of fever and findings that suggest the possibility of meningitis or encephalitis, CT of the head should be followed by lumbar puncture. These tests should not delay the administration of broad-spectrum antibiotics or acyclovir in an ill-appearing febrile child who has had a seizure. If a patient does not return to a normal baseline neurologic status, an EEG is required to evaluate for nonconvulsive status epilepticus.