Investigations

In the child who has clearly fully recovered from the effects of the seizure - i.e. is happy, smiling and cooperative - and there is a clear cause for the pyrexia, no further investigation is required.

If the child has not yet recovered it is necessary to exclude more serious causes of convulsions such as:

• meningitis
  • routine lumbar puncture (LP) is not indicated since the incidence of bacterial meningitis is low in children with febrile seizures (1)
  • the American Academy of Pediatrics (AAP) recommends that
    • LP should be performed in any child who presents with a seizure and fever and has meningeal signs and symptoms or in any child whose history and examination suggests the presence of meningitis or intracranial infection
    • LP is an option in
      • any infant between 6 and 12 months of age who presents with a seizure and fever who is underimmunized or of questionable vaccination status
      • in child who presents with a seizure and fever and is overtreated with antibiotics (2)
• urinary tract infection
  • urine analysis and urine culture specially if a source of infection cannot be identified

Once central nervous system infections are excluded, investigations should be aimed at identifying other causes of fever:

• serum electrolytes, calcium, phosphorus, magnesium, or blood glucose or complete blood cell count should not be carried out routinely to identify the cause of febrile seizure
• investigations carried out in a febrile child can be found at the National Institute for Health and Care Excellence (NICE) guideline on “fever in under 5s: assessment and initial management”

An EEG and neuro imaging have limited value in simple febrile seizures and has no additional diagnostic or prognostic value

• EEG is only indicated if there are repeated convulsions over a period of time, or a single convulsion was unusual, for example if there is a persistent resultant neurological abnormality, or the convulsion lasted more than 20 minutes. In this case the diagnosis of febrile convulsion is in doubt.
• neuroimaging should be considered in the following situations
  • patients with prolonged postictal neurological deficits
  • in recurrent complex febrile seizures
  • children with developmental impairment or with signs of a neurocutaneous syndrome (1)

Reference:

• (1) Patel N et al. Febrile seizures. BMJ. 2015 ;351:h4240
• (2) American Academy of Pediatrics. Neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-94