Physical Examination
Along with the patient’s history, the physical examination should focus primarily on determining a possible seizure etiology. The entire body should be thoroughly evaluated for evidence of trauma. The head should be carefully evaluated for signs of deformity or swelling; the fullness of the anterior fontanel should be carefully assessed; and the pupils should be examined for signs of increased intracranial pressure (ICP). In the older pediatric patient with closed fontanelles in whom a cervical spine injury has been ruled out, assessment of the neck for evidence of meningeal irritation should be performed. Stigmata of underlying medical disease, along with the presence of dysmorphic features associated with particular genetic syndromes, also should be evaluated. In addition, signs of common toxidromes should be sought.
Common Etiologies and Diagnostic Evaluation by Age
Since seizure etiologies and diagnostic evaluation vary greatly along the pediatric age spectrum, it is helpful to divide this population into three main groups: neonates and infants (ages 0-12 months), toddlers and young children (ages 12 months-10 years), and preadolescents and teenagers (ages 11-18 years).
In patients with known seizure disorders, the majority of cases are due to subtherapeutic antiepileptic medications either from a patient “outgrowing” his or her weight-based dose or from medication noncompliance. For the purposes of this article, we have limited our discussion to patients with first-time seizures.
Neonates and Infants.
In infants, hypoxic ischemic encephalopathy (HIE) due to perinatal asphyxia is the most common cause of seizures, the vast majority of which present within the first 24 to 48 hours of life.2 Although EPs may encounter children with seizures caused by HIE, it is rare that these represent an initial seizure. Far more common etiologies of first-time seizures in infants are infection (eg, meningitis, encephalitis, sepsis) and nonaccidental trauma.
Electrolyte Imbalance. Although electrolytes are frequently checked in all age groups with seizures, infants are by far the most likely to experience seizures secondary to electrolyte abnormalities. Therefore, this is the only group in which routine evaluation of electrolytes is recommended. Common conditions associated with electrolyte imbalance include hyponatremia, hypocalcemia and hypomagnesemia, as well as errors of metabolism.
Hyponatremia in infants can be secondary to congenital adrenal hyperplasia or formula overdilution. Hypocalcemia and hypomagnesemia, associated with hypoparathyroidism may be the initial presentation in infants with DiGeorge syndrome. In addition, inborn errors of metabolism frequently lead to hypoglycemic seizures. Thus, in all patients with ongoing seizures refractory to medication, electrolyte abnormalities should be strongly considered.
Computed Tomography. A computed tomography (CT) scan of the head should be highly considered in this patient population as it is often difficult to determine if the patient has returned to neurological baseline. Since the fontanelles are open in infants, they can tolerate larger increases in intracranial volume (whether from blood or mass lesion) before evidence of increased ICP becomes clinically evident.
Lumbar Puncture. A lumbar puncture (LP) to analyze the cerebrospinal fluid (CSF) for infection should be considered in all afebrile infants with seizures, though some recent evidence shows a relatively low yield in such testing.10,11
Toddlers and Young Children.
Within this age group, febrile seizures tend to predominate. A febrile seizure is defined as a seizure occurring between ages 6 months and 5 years that is associated with fever (temperature >38˚C [100.4˚F]) but without evidence of intracranial infection, neurological disease, or another defined cause.1 These seizures can be simple or complex. Simple febrile seizures last less than 15 minutes, have generalized clinical features, and occur only once in a 24-hour period. In contrast, complex febrile seizures last longer than 15 minutes, have focal manifestations, or recur multiple times in 24 hours.3
Simple Febrile Seizures. The vast majority of patients presenting with simple febrile seizures require very limited diagnostic evaluation. If the patient has no evidence of intracranial infection, a normal neurological examination, and is back to baseline mental status, then no further evaluation is necessary. Serum electrolytes should only be checked if the patient does not quickly return to neurological baseline, at which point checking a serum glucose level would be prudent. Any further laboratory testing should be for the sole purpose of determining the source of the patient’s fever.
Most patients do not require CSF testing. In the consensus statement on the neurodiagnostic evaluation of patients with simple febrile seizures, the American Academy of Pediatrics listed only being younger than 6 months of age as a strong indicator to perform an LP. An LP should, however, be considered in patients aged 6 to 12 months who are deficient in their immunizations (especially Haemophilus influenza type B and Streptococcus pneumoniae) and in all patients pretreated with antibiotics as this could mask the signs of meningitis and encephalitis.12