history or physical examination, determination of serum glucose, sodium, and calcium levels are indicated Other ancillary tests that may be indicated, depending on the clinical picture, include serum magnesium, hepatic transaminases, ammonia, serum or urine toxicology tests, electrocardiogram (ECG), and neuroimaging of the brain LP is rarely emergently necessary in the afebrile child without meningeal signs or altered mental status, although it should be considered in neonates even without fever In children with a known seizure disorder, subtherapeutic anticonvulsant levels are the most common reason for breakthrough seizures The name and dosage of anticonvulsant medications used should be elicited, as well as the time of the last dose given, any missed doses, the last change in dosage, and recent levels, if known Intercurrent illness may also play a role because the metabolism of some medications is affected by systemic illness Such children should have blood drawn for measurement of anticonvulsant levels Although many drugs have a standard therapeutic range ( Table 97.3 ), individual patients may require levels outside that range for adequate seizure control; conversely, dose-dependent toxic effects may be observed in some children even at typically therapeutic levels Computed tomography (CT) (or magnetic resonance imaging [MRI], if available) is indicated in the emergency evaluation of prolonged or focal seizures, when focal deficits are present, when there is a history of trauma, when the child has a ventriculoperitoneal shunt, or when there are associated signs of increased ICP For other children with a normal neurologic examination, MRI may be useful in identifying structural anomalies and determining prognosis, but such studies may be deferred to a follow-up visit Cranial imaging is not indicated in the evaluation of simple febrile seizures EEG is also helpful in the evaluation of children with nonfebrile seizures EEG is rarely beneficial in acute management, but children with nonfebrile seizures should be referred for outpatient testing