EEG and MRI Findings in Children with Febrile Status Epilepticus

Abstract & Commentary

By Sotirios Keros, MD, PhD, Instructor, Department of Pediatrics, Division of Pediatric Neurology, Weill Cornell Medical College

Dr. Keros reports no financial relationships relevant to this field of study.

Synopsis: Focal EEG slowing is the most common abnormality seen after febrile status epilepticus, and is associated with radiologic hippocampal injury.

Source: Nordli DR Jr, et al. Acute EEG findings in children with febrile status epilepticus: Results of the FEBSTAT study. Neurology 2012;79:2180-2186.

Although many children with a first febrile seizure will have had a simple febrile seizure, a relatively common and benign childhood illness, a subset will present in febrile status epilepticus, the most severe in the spectrum of febrile seizures. Despite the risks, most children with febrile status epilepticus will have very good outcomes. On the other hand, febrile status epilepticus is associated with medically refractory temporal lobe epilepsy with variable prognosis. However, prospective study data are lacking.

In this paper, the authors investigated EEG and MRI abnormalities associated with febrile status epilepticus from the ongoing, prospective Consequences of Prolonged Febrile Seizures (FEBSTAT) study. Children eligible for enrollment were between 1 month and 5 years of age and presented with febrile seizures (temperature > 101° F) lasting > 30 minutes and did not otherwise have a history of febrile seizures, acute brain injury or infection, or severe neurologic disability. EEGs were obtained within 72 hours, and were interpreted by multiple investigators in a blinded manner. MRIs were also interpreted by radiologists blinded to the clinical history.

Of the 199 children enrolled, 58% were younger than 18 months of age, 53% were male, 57% had continuous febrile status epilepticus, 86% were developmentally normal, and 80% had no history of prior febrile seizure. The peak median temperature was 102.7° F (IQR 101.5°-103.5° F) and the median duration of seizures was 70 minutes (IQR 47-110). Focal status epilepticus was present in 68%.

Fifty-five percent of all EEGs were considered to be normal. Only 7% of the EEGs had epileptiform activity, primarily in the form focal sharp waves or spikes, of which half were located in a temporal lobe. Non-epileptiform abnormalities were noted in 43% of the children, consisting of focal slowing (24%), diffuse slowing (11%), and focal attenuation (13%). Of the 47 cases with significant focal slowing, 45 were in the temporal region. Focal slowing was more common on the right (77%) as was focal attenuation (60%). There were 19 children who had both lateralizing seizures and focal slowing or focal attenuation. Of these, in 79%, the EEG abnormality was on the expected side, while in 21% it was contralateral to the side of the expected cortical origin of the seizure based on lateralizing signs.

MRI abnormalities were noted in approximately 23% of study patients. MRI abnormalities, primarily of the hippocampus, were positively associated with focal slowing or attenuation on EEG, with hippocampal T2 signal changes showing the strongest association. In a previous paper based on the same group of patients,1 there were no hippocampal T2 signal abnormalities in a control group of 96 children who presented with only simple febrile seizures as opposed to those with febrile status epilepticus.

Commentary

This is a much-needed study that hopefully will provide, in the future, an opportunity to answer the question of whether febrile status epilepticus is indeed a risk factor for hippocampal sclerosis and medically refractory temporal lobe epilepsy. Very few patients had any epileptiform activity on EEG, but almost half had slowing or attenuation, a marker of cerebral dysfunction. As the authors note, this is consistent with a model where status epilepticus leads to brain injury that can in turn cause epilepsy. Ideally, the study will be able to identify risk criteria based on these early EEG and MRI findings, as well as follow-up EEGs and imaging, and provide an opportunity to test interventions that may prevent intractable epilepsy and improve overall outcomes in those patients most at risk.

Reference

  1. Shinnar S, et al. MRI abnormalities following febrile status epilepticus in children: The FEBSTAT study. Neurology 2012;79:871-877.