The FEBSTAT study team of investigators determined whether febrile status epilepticus (FSE) produces acute hippocampal injury that evolves to hippocampal sclerosis. FSE was defined as a febrile seizure (FS) lasting 30 minutes or longer or repetitive FSs, lasting at least 30 minutes without regaining alertness. Acute MRI performed after FSE in 226 children aged 1 month to 6 years showed hippocampal T2 hyperintensity in 22 (10%) children, maximum in Sommer's sector, and in association with increased hippocampal volume. Follow-up MRI obtained ∼1 year later on 14 of the 22 with acute hyperintensity showed hippocampal sclerosis (HS) in 10 and reduced hippocampal volume in 12. In contrast, follow-up of 116 children without acute hyperintensity showed abnormal T2 signal in only 1 (after another episode of FSE). Compared to controls with simple FS, FSE subjects with normal acute MRI had abnormally low right to left hippocampal volume ratios, small hippocampi initially, and reduced hippocampal growth. Impaired growth of normal-appearing hippocampi suggests subtle injury after FSE, even in the absence of T2 hyperintensity. The relationship of these findings to temporal lobe epilepsy requires longer follow-up. [1]

COMMENTARY. The combined MRI findings of increased hippocampal signal and atrophy are considered reliable indicators of HS [2]. In 1964, Falconer MA, neurosurgeon, and associates at Maudsley Hospital, London, UK, recorded the pathological findings in 100 consecutive surgical patients with temporal lobe epilepsy and found a possible association between mesial temporal sclerosis and febrile convulsions in childhood [3]. Sixty years later we are still uncertain of the exact relationship between temporal lobe epilepsy and febrile seizures. Multiple epileptogenic factors may be involved, including HHV6/HHV7 viremia, developmental delay, and pre-existing congenital abnormalities. It is difficult to determine whether HS predates or is the consequence of febrile seizure. As concluded in an invited commentary (Can febrile status cause HS?), the chicken or egg controversy remains unsettled [4]. Of the 9 patients (4% of 226) who developed changes suggestive of HS, 5 had other MRI abnormalities. Longer follow-up should determine the outcome and occurrence of TLE in this cohort.