EM Nerd-A Brief Addendum to the Adventure of the Red-Headed League

What is the clinical significance of a post traumatic seizure (PTS) in children presenting to the Emergency Department following minor head trauma?

This is a question surrounded by myth and dogma. As with most questions regarding traumatic brain injury (TBI) in children, the PECARN authors have come to our aid.

Badawy et al published a secondary analysis of the massive PECARN dataset in Academic Emergency Medicine, examining the prevalence of TBI and recurrent seizures in children presenting to the Emergency Department following a PTS (1). The original PECARN trial was a massive undertaking involving 25 Emergency Departments, enrolling 42,242 children in their derivation and validation of the PECARN head CT rule. The authors identified the children in this cohort who presented following a PTS, defined as a witnessed seizure episode following a traumatic event. The seizures were categorized according to their timing in relation to the initial event, (immediate (on impact), within 30 minutes, or more than 30 minutes after the traumatic event), and in terms of the length of witnessed seizure activity (less than 1 minute, 1-4 minutes, 5-15 minutes or greater than 15 minutes).

The authors examined the prevalence of TBI found on CT, the need for neurosurgical intervention, and the rates of recurrent seizures in patients that presented following TBI. Of the 42,424 children included in the original PECARN dataset, 536 (1.3%) had a PTS and were included in the final analysis and 466 (86.9%) of these patients received a CT scan in the Emergency Department. 72 (15.5%) children who experienced a PTS, had findings concerning for TBI on head CT and 20 required neurosurgical intervention.

The rate of TBI in children presenting with PTS is high, and a concerning portion of these injuries required neurosurgical intervention. The authors demonstrated a stepwise increase in the risk of TBI corresponding to the time from injury to seizure onset as well as the duration of seizure activity. But with any of these predictive models, the question should not be how does any individual variable predict the outcome in question, but how it performs when used in concert with the remainder of the clinical presentation.

This study and the original PECARN publication highlight, that while some children who present with TBI following a traumatic event will have a PTS heralding the injury, almost all will present with other clinical signs announcing the presence of that injury. Of the children who experienced PTS with none of the factors included in the original PECARN prediction rule, only one had an injury identified on CT. This patient was found to have pneumocephalus and was discharged directly from the ED. A finding that the original PECARN dataset would not have considered a clinically important TBI (ciTBI)(2). Of the children with PTS who had a ciTBI requiring neurosurgical intervention, all but one exhibited an altered level of consciousness. Even this single patient had multiple PECARN variables concerning for ciTBI. Of the 15 patients who experienced recurrent seizures following an episode of PTS, only one patient with a GCS of fifteen (0.3%) experienced a subsequent seizure.

So often we become mesmerized by big data, lured in by the statistical confidence these large sample sizes provide. Taken out of context many data points can appear to be strong predictors of adverse outcomes. But is important to remember that these variables are just one small piece of the greater picture. Each representing a small part of a larger story. In this case, it is a tale of children presenting with ciTBI after a traumatic event who bear an extraordinary resemblance to children presenting with ciTBI after a traumatic event. When examined in isolation PTS appears to be a strong predictor of TBI, however in this full clinical context, it adds very little predictive value.

Sources Cited:

Badawy MK, Dayan PS, Tunik MG, et al. Prevalence of Brain Injuries and Recurrence of Seizures in Children with Post Traumatic Seizures. Acad Emerg Med. 2017;
Kuppermann N, Holmes JF, Dayan PS, Hoyle JD, Atabaki SM, Holubkov R, et al. Identification of children at very low risk of clinically important brain injuries after head trauma: a prospective cohort study. Lancet 2009; 374:1160-70.