Febrile Seizures Workup

Updated: Sep 19, 2017
  • Author: Nooruddin R Tejani, MD; Chief Editor: Kirsten A Bechtel, MD  more...
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Workup

Laboratory Studies

In children under the age of 5 with complex febrile seizures, over one-third of experienced pediatric emergency physicians would do extensive workup, nearly half would admit, but variability exists in the approach to optimal management of patients with CFS. Past studies support more aggressive workup for patients under the age of 18 months, but future prospective studies on this subject are warranted. [32]

Routine laboratory studies usually are not indicated for febrile seizure unless they are performed as part of a search for the source of a fever.

Electrolytes assessments are rarely helpful in the evaluation of febrile seizures. [6]

Patients with febrile seizures have an incidence of bacteremia similar to patients with fever alone. [33]

A study found the European children with febrile seizures have lower Ferritin than those with fever alone, and iron deficiency, but not anemia, is associated with recurrence. The study also suggested that iron status screening should be considered to help determine which children with febrile seizures may be at risk for recurrence. [34]

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Imaging Studies

A CT scan should not be performed in the evaluation of a child with a first simple febrile seizure.

A CT scan should be considered in patients with complex febrile seizures. However, a study by Teng et al analyzed data in 71 children with first complex febrile seizure. [35] Fifty-one (72%) had a single complex feature (20 focal, 22 multiple, and 9 prolonged), and 20 (28%) had multiple complex features. None of the 71 patients (1-sided 95% confidence interval, 4%) had intracranial pathologic conditions that required emergency neurosurgical or medical intervention. Forty-six had normal acute scans; the rest were normal on clinical follow up without a scan. The confidence interval means that this study cannot exclude a risk of intracranial pathology of 4% or less.

Kimia et al reported a retrospective cohort review in children presenting with first complex febrile seizure (CFS). Of 526 subjects with CFS, 268 had emergent head imaging: 4 had a clinically significant finding; 2 had intracranial hemorrhage; 1 had acute disseminated encephalomyelitis; and 1 patient had focal cerebral edema (1.5%; 95% CI, 0.5-4%). Assigning low risk to patients not imaged and not returning to the emergency department within a week of the original visit, the risk of intracranial pathology was 4 (0.8%; 95% CI, 0.2-2.1%). Three of these 4 patients had other obvious findings (nystagmus, emesis, and altered mental status; persistent hemiparesis; bruises suggestive of inflicted injury). In the absence of other sign and symptoms, patients presenting with CFS are at very low risk for intracranial pathology. [36]

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Other Tests

An electroencephalogram (EEG) is not necessary in the routine evaluation of a child with a simple febrile seizure. In a prospective study, Nordli et al recruited 199 children with febrile status epilepticus (severe type of complex febrile seizure) within 72 hours of presentation. Of these, 45.2 % had an abnormal EEG with focal slowing and attenuation seen maximally over the temporal areas in almost all cases and were highly associated with MRI evidence of hippocampal injury. [37]

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Procedures

Lumbar puncture

Controversy exists regarding the need for a lumbar puncture in a child presenting with a simple febrile seizure. Lumbar puncture is not needed for young children with first simple febrile seizure. [38]

Certainly, meningitis can present with a seizure, although the seizure usually is not the only sign of meningitis. Patients who have a first-time febrile seizure and do not have a rapidly improving mental status (short postictal period) should be evaluated for meningitis.

Several reviews of the medical literature report less than 5% incidence of meningitis in children presenting with seizures and fever.

Hom and Medwid, in an evidence-based review, examined the risk of bacterial meningitis as diagnosed by lumbar puncture in children presenting to the emergency department with a simple febrile seizure. The study population consisted of fully immunized children aged 6-18 months with an unremarkable history and normal physical examination. Of 461 children, 150 enrolled for febrile seizure underwent lumbar puncture to rule out meningitis. The rate of bacterial meningitis was 0% (95% CI, 0-3%). [39] Fletcher and Sharieff also determine that acute bacterial meningitis (ABM) is rare in patients presenting with a first complex febrile seizure. Patients presenting only with 2 short febrile seizures within 24 hours may be less likely to have ABM, and may not require lumbar puncture without other clinical symptoms of neurological disease. [40]

Risk factors for meningitis in patients presenting with seizure and fever include the following:

  • A visit to a healthcare setting within the previous 48 hours
  • Seizure activity at the time of arrival in the ED
  • Focal seizure, suspicious physical examination findings (eg, rash, petechiae) cyanosis, hypotension, or grunting
  • Abnormal neurologic examination
  • Pretreatment with antibiotics, as it can mask signs and symptoms of meningitis

In 1996, the American Academy of Pediatrics (AAP) recommended that a lumbar puncture be strongly considered in patients younger than 12 months presenting with fever and seizure. [2] The AAP also recommended that a lumbar puncture be considered in patients aged 12-18 months. A lumber puncture is not routinely necessary in patients older than 18 months. This recommendation is conservative, but it takes into account the difficulty in recognizing meningitis in infants and young children and the range of experience in the evaluation of pediatric patients among healthcare providers.

In 2011, the AAP revised this guideline. It no longer recommends routine lumbar puncture in well-appearing, fully immunized children who present with a simple febrile seizure and makes lumbar puncture an option in infants age 6-12 months who are deficient in Haemophilus influenzae or Streptococcus pneumoniae immunizations or when immunization status cannot be established. [41]

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