Abstracts

There is continued debate on whether status epilepticus can cause acute hippocampal damage, which could lead to mesial temporal lobe epilepsy. Previous reports in children have shown enlarged hippocampal volumes (HV) within five days of prolonged febrile seizures (PFS). Our purpose was to assess HV and signal changes on diffusion weighted imaging (DWI) within five days of PFS and compare them with the PFS duration. We studied 10 children (mean age: 36 [plusmn] 21 months, range 11 months to 5 years) within five days of a first episode of PFS (a seizure or series of seizures lasting for [ge] 30 minutes, without return of consciousness between the seizures). The hippocampus was segmented manually on a high-resolution MRI (T1-FFE sequence, 1mm3 isotropic voxels) and signal intensity abnormalities were evaluated visually on DWI (TR 2700 TE 90). The patients had no neurological abnormalities before the onset of seizures. Seizure duration ranged from 40 to 95 minutes. In 7/10 patients, seizures were intractable and lasted more than 60 minutes despite intravenous infusion of diazepam. In the three other patients, seizures were controlled by single dose of diazepam. HV in patients were compared with those to of 12 neurologically normal controls (age mean 32 [plusmn] 16 months, range 15 months - 5 years). HV abnormalities were correlated to PFS duration. Both the left HV and right HV were larger in patients than controls (3000 [plusmn] 499 mm3 vs. 2790 [plusmn] 312 mm3 in the left; and 3194 [plusmn] 416 vs. 3060 [plusmn] 309 mm3 in the right). However, the difference was not significant. When considering only patients with PFS longer than 60 mins, HV were significantly larger than in controls (left 3217 [plusmn] 401 mm3, p = 0.02; right 3390 [plusmn] 315 mm3, p = 0.04). In patients, there was also a positive correlation between HV and PFS duration (left r = 0.75, p = 0.01; right r = 0.64, p = 0.04). DWI showed unilateral hippocampal hyperintensity in three patients with intractable seizures, and ipsilateral thalamic hyperintensity in one of them. Large HV and hippocampal hyperintensity on DWI were seen in patients with intractable PFS. Our results suggest that medically intractable PFS longer than 60 minutes may cause structural changes in limbic structures that could promote epileptogenesis.