Abstracts

There is continued debate on whether status epilepticus can cause acute hippocampal damage leading to 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 serial changes in the limbic circuitry using HV and diffusion weighted image (DWI) in children with PFS., We studied 12 children (mean age: 32 [plusmn] 21 months, range 10 months to 5 years) within 5 days of a first episode of PFS (duration range: 40 to 95 minutes). HV were measured on high-resolution MRI (T1-FFE sequence, 1mm3 isotropic voxels) using manual segmentation and signal intensity was evaluated visually on DWI (5mm thickness with 1.5 mm gaps, b=1000 s/mm2, TR/TE 2700/90). Patients had no neurological abnormalities before the onset of seizures. In 7/12 patients, PFS lasted more than 60 minutes despite intravenous diazepam. In the 5 others, seizures were controlled by a single dose of diazepam. HV in patients were compared with those of 13 healthy controls (age mean 31 [plusmn] 16 months, range 15 months - 5 years). Those patients who presented with DWI abnormalities (n=3) were re-examined few weeks later and HV were re-measured approximately after 1 month. HV was correlated to PFS duration., HV in patients were not significantly different from those of controls. However, patients with PFS longer than 60 minutes had significantly larger HV than controls. There was a positive correlation between HV and PFS duration (left: r = 0.75, p = 0.01; right: r = 0.64, p = 0.04). DWI showed a unilateral hippocampal hyperintensity in 3/7 patients with PFS, associated with ipsilateral thalamic hyperintensity in 2 of them. Hippocampal hyperintensity was reduced at the time of follow up. HV was re-examined in nine patients. Volume reduction was observed bilaterally in seven patients, and in the right side of another one patient. In the 3 patients with DWI abnormalities, re-examination revealed a significant HV reduction., Intractable, prolonged PFS may lead to an acute increase in hippocampal volume and hyperintense signal, possibly related to cytotoxic edema. These transitory changes are rapidly followed by a loss in hippocampal volume. Prolonged PFS may cause structural changes in limbic structures that could promote epileptogenesis.,