Complex Febrile Seizures – More Complex than Simple.

I think that it is fair to say that we are all accustomed to the management of Simple Febrile Seizures. Essentially, you ensure that the case fits the defined criteria (age = 6mos-5yrs; generalized Sz; lasts <15min; child returns to baseline after short post-ictal period; and only a single Sz in 24hrs) and then evaluate the patient as if he/she only had the fever {see Morsel from April 1, 2011}. That doesn’t require to many synapses to fire; however, more cognitive muscle is required for Complex Febrile Seizures.

Febrile Seizures

  1. Most common childhood seizure (affecting 2-6% of all children)
  2. Classified as either Simple or Complex
    1. Simple
      1. Are “simple” – see above for criteria
      2. Those who fit the criteria have no greater risk for meningitis than similar patients with fever alone… so evaluate the fever appropriately.
    2. Complex
      1. May have longer duration, may be multiple in 24 hr period, and may be focal.
      2. If the child has not returned to baseline (which would be the case if he/she was having a prolonged seizure) it can be difficult to prospectively discern it from more concerning etiologies, like meningitis.

Seizures and Meningitis

  1. Prevnar and HiB vaccines have reduced the incidence of meningitis, and the true numbers are not yet known.
  2. While, it is appropriate to estimate the overall incidence as having been greatly reduced from pre-vaccine dates, this decrease does not necessary correlate with a decrease in incidence in Meningitis in patients presenting to the ED with a non-Simple Febrile Seizure.
  3. A recent study (Pediatrics July 2010, Vol 126, pp. 62-69) found that patients who were retrospectively deduced as having had a Complex Febrile Seizure had a low rate of bacterial meningitis. That is great…. But let us consider a few issues:
    1. Their population was >90% vaccinated (yours may not be).
    2. Their study only had 3 cases of bacterial meningitis… Does this point to low overall incidence, or to an underpowered sample size to capture a serious condition with low incidence?
When are you able to make the diagnosis of Complex Febrile Seizure? Is it a diagnosis that can be made prospectively at the bedside while evaluating the child in the ED? The child arrives after 40 minutes of focal seizure activity that doesn’t show any sign of stopping… he is febrile and unresponsive. He may have a Complex Febrile Seizure… but how do I tell the difference, in that moment, from a seizure due to bacterial meningitis?

(4) Additionally, the association of Seizure and Meningitis is well established.
(5) It is important to note that Seizure is seldom the sole finding of a patient with meningitis (so thorough exam is imperative – petechiae?)
(6) Most importantly, patients who present with a seizure that is eventually diagnosed as a Complex Febrile Seizure represent a heterogeneous group.

My Humble Opinion and Approach

  1. I am trained to assume the worst… Fever + Seizure = Meningitis; but there is one well known caveat…
  2. If the patient fits Simple Febrile Seizure, then risk of meningitis is the same as if Seizure did not occur… so do thorough physical exam and perform age-appropriate work-up of the fever.
  3. If the child has had more than one Seizure in a 24 hour period, but otherwise fits the definition of Simple Febrile Seizure (is alert and you can perform an appropriate neuro exam and clinical assessment), then this case can be treated as if it were a Simple Febrile Seizure (although I would likely observe the patient to ensure there were not any more Seizures or change in mental status).
  4. If the child arrives and could officially fit the criteria for Complex Febrile Seizure (i.e. seizure is prolonged) but the child cannot be evaluated because of prolonged postictal period or continued seizures, I think you need to err on the side of caution and treat as if there is a serious life threatening condition present. I am completely ok with my colleagues upstairs telling me later that the patient had a Complex Febrile Seizure after the serious medical threats have been ruled-out rather than playing the odds and being wrong … I don’t like to gamble with kids’ brains. It boils down to whether you believe you can confidently assess the child for evidence of serious bacterial infection.

Certainly, I welcome your comments to the contrary or in agreement.

Kimia A, Ben-Joseph EP, Rudloe T, Capraro A, Sarco D, Hummel D, Johnston P, Harper MB. Yiled of Lumbar Puncture Among Children Who Present With Their First Complex Febrile Seizure. Pediatrics. Vol 126(1); July 1 2010: pp. 62-69.


Sean M. Fox
Sean M. Fox
Articles: 583


  1. Dear Sir,
    thank you for your insight.
    my son had a seizure last month and it was for about 1 mt . the seizure happened again last week but twice. 12 hrs between the two seizures. all the three seizures lasted 1 mt and like simple seizure. is it complex? what is your experience on such matter?

    • I am sorry that your child and your family are dealing with this recent development. I, obviously, cannot give out specific medical advice on the internet. I would say that your child should be seen and evaluated by your primary doctor and, likely, see a pediatric Neurologist. Your child’s seizures deserve more attention than can be given with the limited information available online.

      I wish you all the best,

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