Febrile seizures are common in the general pediatric population, with an incidence of 2% to 5%.
The definition of a simple febrile seizure is a generalized tonic-clonic seizure lasting <15 minutes with a fever 38°C (100.4°F) in a child 6 months to 5 years of age that occurs only once in a 24-hour period.51,52 The American Academy of Pediatrics holds that no blood studies, neuroimaging, or electroencephalogram is necessary for most simple febrile seizures and the evaluation should focus on identifying the source of fever (e.g., urinalysis and culture).51,52,53,54 The American Academy of Pediatrics does recommend that a lumbar puncture be strongly considered in these children when there are clinical signs or symptoms that suggest meningitis or intracranial infection. Consider lumbar puncture for infants 6 to 12 months of age who are unimmunized for Haemophilus influenza type B or streptococcus pneumonia and those taking antibiotics, which can mask the signs and symptoms of meningitis.51,52
Parents of children experiencing a simple febrile seizure need education regarding the natural history of febrile seizures. Only 50% of children <12 months and 30% of children >12 months will have another simple febrile seizure.54 Having a febrile seizure does not mean that a child will develop epilepsy. In fact, children who experience a simple febrile seizure have roughly the same 1% risk as the general population of developing epilepsy by the age of 7 years. Factors that increase that risk to 2% to 4% include a family history of seizures, multiple febrile seizures, and first febrile seizure before 12 months of age. Other factors that increase the risk of recurrence include developmental delay, focal seizures, Todd's paralysis, focal neurologic findings on examination, and abnormal findings on electroencephalogram, CT, or MRI.54
Complex febrile seizures are defined as seizures with fever that last >15 minutes, that recur within a 24-hour period, are focal, or occur in children <6 months or >5 years of age without any signs of serious infection.51,54 Routine blood tests and imaging are not indicated, even in the setting of complex febrile seizure, if the child returns to baseline in the ED. Consider lumbar puncture for prolonged febrile seizures: one study noted that children with fever and seizures lasting >30 minutes had a significantly higher incidence of bacterial meningitis (15% to 18%) than children with simple febrile seizures (0.4% to 1.2%)55; another study, however, found only two patients with meningitis among 526 complex febrile seizures, and both had clinical signs and symptoms of meningitis.56
Children with a prolonged seizure associated with a fever who appear ill should undergo evaluation to rule out serious bacterial infection in the blood and cerebrospinal fluid,29,56 although parenteral antibiotics should not be delayed while sick children are being evaluated.55
Treatment of Febrile Seizure
Anticonvulsant therapy is not recommended for simple febrile seizures since side effects outweigh the minor risks of seizure recurrence.54 Although antipyretics are indicated in children with fever, there is no evidence that antipyretics can prevent subsequent febrile seizures.54,57
In 2000, the American Academy of Neurology published a practice guideline for the evaluation of a first afebrile seizure in a child, which pertains only to the child who returns to baseline following the seizure.58,59 The guideline suggests that routine laboratory evaluations and emergent neuroimaging are not necessary. If there is evidence that the child had vomiting or diarrhea, is dehydrated, or fails to return to baseline, laboratory tests are recommended. A toxicology screen should also be included if there is concern for drug exposure or substance abuse or the cause of the seizure cannot be determined. Lumbar puncture is unnecessary unless there is a concern for meningitis or encephalitis. An electroencephalogram should be performed, although the timing is unclear: an electroencephalogram within 24 hours of the seizure is most likely to show abnormalities; however, an electroencephalogram within 24 to 48 hours may also show some transient postictal slowing.
Indications for emergent head CT include children with a condition predisposing them to intracranial abnormalities, those with focal seizures, and children younger than 33 months of age with new-onset seizures.9 Patients who do not meet the criteria for high risk and are well appearing may be discharged with outpatient follow-up. Outpatient MRI should be considered in any child with any of the following: significant cognitive or motor impairment, abnormal findings on neurologic examination, abnormal electroencephalogram findings, partial seizure, or infants <1 year of age.58,59
The overall risk of recurrence after a single afebrile seizure is about 40%.58,59,60 Factors that increase this risk are a family history of seizures, previous febrile seizures, developmental delay, abnormal CT or MRI findings, presence of focal deficits on neurologic examination, Todd's paralysis, abnormal electroencephalogram findings, and seizure occurring during sleep.58,59 Most neurologists do not recommend initiating daily anticonvulsant medications after a first seizure.59 Noninitiation of treatment does not increase the risk of epilepsy, prognosis, or increase the risk of intractable epilepsy or death, but does allow the physician to better clarify the type and frequency of seizures and also avoids the side effects of unnecessary daily anticonvulsant medications in those not destined to for recurrence.58,59,60
Neonates do not have a fully developed neurologic system, and seizures in this age group can be subtle, are more likely to be focal, and often carry a poor prognosis.44 Seizures occur in 1.4% of full-term infants and 20% of premature infants.
Identifying seizure activity in the neonate and distinguishing it from normal newborn myoclonus and jitters can be challenging. Subtle focal movements or stereotyped activities (e.g., lip smacking, eye deviation, or bicycling) may represent seizure activity; neonates less often have generalized tonic-clonic seizures.44 Apparent life-threatening events with pallor or cyanosis and a change in muscle tone may be a manifestation of seizure activity.
A birth and maternal history may identify risks for congenital or neonatal infection (e.g., herpes simplex virus, cytomegalovirus, or group B streptococci) or potential withdrawal from maternal narcotics.44 Complications with labor and delivery may suggest birth asphyxia with subsequent seizures. Regardless of the history or presence of fever, neonates with witnessed seizures require extensive evaluation. Obtain cultures of blood, urine, and cerebrospinal fluid and test for herpes simplex virus and begin empiric parenteral antibiotics and acyclovir. Toxicologic evaluation may provide the physician with evidence of withdrawal or overdose of abused substances. Neonates with seizures are more likely to have electrolyte abnormalities than older children, and electrolytes including calcium and glucose should be measured. Consider head CT for concerns of nonaccidental trauma, intracranial hemorrhage, infarction, or mass (even without external signs of injury). Finally, if inborn errors of metabolism are suspected, obtain serum levels of lactate and ammonia, as well as serum amino acids and urine organic acids (see chapter 144, Metabolic Emergencies in Infants and Children).38 All neonates with witnessed seizure require admission to the hospital.
Treat the actively seizing neonate with benzodiazepines as with older children; consider phenobarbital for second-line therapy. Identify and treat hypoglycemia and electrolyte abnormalities.
SEIZURES IN CHILDREN WITH EPILEPSY
Parents, old records, and pediatric neurologists can be very helpful in identifying past causes of seizures, successful (and unsuccessful) treatments, and other issues that can help direct the care of patients with epilepsy presenting to the ED with seizure. Table 135-6 lists common anticonvulsants prescribed for children with epilepsy. Subtherapeutic drug levels may result when a child outgrows a previously prescribed dose, vomits medications due to an intercurrent illness, starts a new medication (due to changes in drug pharmacokinetics from drug interactions), or does not adhere to the original drug regimen. Subtherapeutic drug levels are a common cause of breakthrough seizures, and serum levels of home antiepileptic medications should be checked as part of the routine ED evaluation of these patients, although results may not be readily available for some newer agents. When low levels are identified, the cause should be determined so that proper adjustments in daily anticonvulsant dosing can be made with advice from the patient's neurologist.
TABLE 135-6List of Anticonvulsants Commonly Used in Children ||Download (.pdf) TABLE 135-6 List of Anticonvulsants Commonly Used in Children
Children with epilepsy may have a lower seizure threshold with febrile illness, even with therapeutic anticonvulsant levels, and the ED evaluation in these situations may be limited to determining the source of fever. Lumbar puncture is unnecessary unless there are clinical signs or symptoms of meningitis.
SEIZURES IN CHILDREN WITH VENTRICULOPERITONEAL SHUNTS
Many children with ventriculoperitoneal shunts also have a medical history of seizures. Considerations include underlying epilepsy, shunt malfunction, and central nervous system infection. The standard approach to the evaluation for a shunt malfunction consists of a radiographic ventriculoperitoneal shunt series and a head CT or "quick brain MRI" to evaluate for increased ventricular size. If central nervous system infection is a concern, a pediatric neurosurgeon should be consulted and the shunt tapped for cerebrospinal fluid analysis and culture. Seizures in children with ventriculoperitoneal shunts are more likely to be related to shunt infection than to mechanical shunt malfunction, especially if associated with fever,61 and the risk of infection increases in children with a history of a prior shunt infections.62 In most cases, consulting past medical records, parents, and the neurosurgeon who placed the shunt is needed for prudent decision making.
"Impact seizures" (seizures that occur within minutes of head trauma) do not, by themselves, increase the risk of having an intracranial injury; seizures that occur in a more delayed fashion, however, are more indicative of severe injuries. Guidelines for the ED evaluation and management of head injury increasingly focus on strategies for risk stratification in order to avoid the potential long-term effects of ionizing radiation and are discussed in detail in chapter 138, Head Injury in Infants and Children. Children with identified intracranial injury and a witnessed seizure should be treated with a loading dose of antiepileptic medication, typically fosphenytoin 20 milligrams/kg IV, to prevent short-term recurrence that can worsen traumatic brain injury and increase intracranial pressure; benzodiazepines remain first-line treatment for active seizures in the setting of trauma.
Infants and toddlers presenting with vague complaints and seizures may be the victims of abusive head trauma (see chapter 110, Pediatric Trauma), which can present without external signs of injury. Most children with abusive head trauma are <2 years of age, and the majority occur in the first year of life (shaken baby syndrome).63,64 Subdural hematoma is the most often identified inflicted intracranial injury in these infants. Maintain a high index of suspicion for trauma in the setting of afebrile seizures in infants. If intracranial injury is identified, a more complete evaluation for other abusive injuries is necessary, including skeletal survey, retinal examination by an ophthalmologist, screening for blunt abdominal trauma (liver and pancreatic enzymes), and bleeding studies.63
Acknowledgments: The author gratefully acknowledges the contributions of Michael A. Nigro, MD, the author of this chapter in the previous edition; Dr. Nanette Dudley, MD (Pediatric Emergency Medicine, University of Utah), Dr. Jeff Schunk, MD (Pediatric Emergency Medicine, University of Utah), Dr. Kim Statler, MD (Pediatric Intensive Care, University of Utah), and Pamela Carpenter, graphic design specialist.