Hippocampal Growth after Febrile Status: FEBSTAT Five Year Follow-Up

The FEBSTAT study (Consequences of Prolonged Febrile Seizures in Childhood) is prospectively examining long term outcomes of febrile status epilepticus ( FSE). We have previously reported the results of the acute2 and 1 year follow-up3 MRIs in the FEBSTAT cohort. This report describes the results of the 5 year follow-up MRIs on the FEBSTAT cohort. In this analysis we have integrated brain growth data from a large group of older normal control subjects obtained from the NIH MRI Study of Normal Brain Development. One hundred and three FSE subjects with 5 year follow-ups (Mean FU 5.45; SD 1.06; Median 5.30 yrs) are included in this report. The major findings of this study are, i) atrophy and T2 signal hyperintensity seen acutely and at one year follow-up in affected hippocampi continues into the 5 year follow up at 5 to 10 years of age and, ii) hippocampi of male FSE subjects with no hippocampal T2 signal increase and normal morphology on MRI are definitely smaller on volumetric measurement than control male hippocampi for at least the first 5 to 7 years after FSE, but female FSE hippocampi are much less affected, iii) in the absence of recurrent episodes of FSE, the finding of normal hippocampal signal on the acute post-FSE MRI reliably predicts normal hippocampal signal in later follow up MRIs and iv) hippocampal malrotation (HIMAL), a developmental abnormality associated with FSE4, slows the growth of the hippocampus.