It’s pretty clear that you don’t need to do an LP to rule out meningitis in simple febrile seizures. But what about complex febrile seizures? What if you consult a Neurologist and they recommend one? Read on to find answers to this pertinent question.

First, what defines a complex febrile seizure

Complex febrile seizures are generally defined as follows;

  • Focal onset Which admittedly can be hard to define since you are relying on caregiver report
  • Prolonged >15 minutes (which is a really long time, though some advocate for a 10 minute limit)
  • Recurrent within 24 hours

In most series ≤20% of febrile seizures are complex, and in general focal features are more rare than a prolonged seizure. Most kids who have a complex febrile sierra do so their first time. This doesn’t mean that all subsequent febrile seizures will be complex. Conversely, it is more rare for a simple febrile seizure child to have a subsequent complex one – though it does happen about 5% of the time.

Complex febrile seizures are important, as children that have them are more likely to have abnormal development and be younger in age, see Hesdorffer et al. for more information.

This is different than febrile status epilepticus

Febrile status epileptics seizures last >30 minutes. There is evidence that an LP is warranted in this group, but this is beyond the scope of this post. So let’s move on.

Is there any evidence on the need for LP?

The answer is yes, there’s evidence, and no, you probably don’t need to do an LP. Let’s take a look at a couple of studies.

Kimia et al. Yield of lumbar puncture among children who present with their first complex febrile seizure. Pediatrics, 2010

This was a retrospective cohort of 526 children with complex febrile seizures. The rate of LP was 64%, though the data were from 1995-2000, crossing vaccine eras. Only 14 (2.7% [95% confidence interval [CI]: 1.5-4.5]) has CSF pleocytosis. Only 3 of these kids had bacterial meningitis. One had S. pneumo, and was apneic with a bulging fontanelle, and another was unresponsive. Another with CSF pleocytosis had a positive blood culture for S. pneumo, but a negative CSF culture. No patients in this cohort without an LP performed came back to the hospital with bacterial meningits.

Fletcher et al. Necessity of Lumbar Puncture in Patients Presenting with New Onset Complex Febrile Seizures. Western J Emerg Med, 2013

This retrospective cohort of 193 children 6 months to 5 years with first complex febrile seizures between 2005-2010 saw 136/193 (70%) getting LPs, with only 1/14 that had pleocytosis on the CSF having bacterial meningitis. LPs were more likely in kids with seizure focality, status epilepticus, or a need for intubation. 43/193 had ≥2 seizures in 24 hours. In my practice I see this more often than locality or length >15 minutes. None of the 17/43 that had an LP performed had bacterial meningitis.

Guedj et al. Do All Children Who Present With a Complex Febrile Seizure Need a Lumbar Puncture? Ann Emerg Med, 2017

This multi center retrospective study of 839 children with complex febrile seizures saw rates of bacterial meningitis (0.7%) and HSV meningitis (0%). All 5 patients with bacterial meningitis had signs and symptoms of meningitis.

Lee et al. Complex Febrile Seizures, Lumbar Puncture, and Central Nervous System Infections: A National Perspective. Acad Emerg Med, 2018

A large national database report of almost 29,000 children with complex febrile seizures from 2007-14 saw declining rates of LP overall. The rate of CSF infection (not specified virus or bacteria unfortunately) was 0.3% (80 encounters, 95% CI = 41-112). They also noted that 51.0% (95% CI = 47.9%-54.1%) were admitted. This study was limited by the data source, but also shows on a macro level just how rare CSF infection is.

Are there any guidelines? I like guidelines…

The answer is no, not really… See the AAP’s guideline for simple febrile seizures below. We can abstract some