Background: The causal relationship of complicated febrile seizures in infancy with hippocampal injury and subsequent development of hippocampal sclerosis/atrophy is an often debated issue in neuropediatrics.
Case report: We report the case of a 16-month-old boy with unusually rapid onset of hippocampal injury and development of cortical hemiatrophy after a complicated febrile seizure of 30 minutes duration. The generalized tonic-clonic seizure stopped after 10mg diazepam, however, the boy presented with a left-sided hemiparesis and anisocoria. At admission, the patient suffered from a throat infection with a body temperature of 39.3°C, but he had no history for previous seizures. Family history was unremarkable. Laboratory findings and CSF analysis were normal except for CrP (13mg/L) without evidence for viral or bacteriological infection. Twenty hours after the seizure, diffusion-weighted cerebral MRI imaging showed a focal swelling in the right hippocampus region suggesting intracellular oedema. While the clinical symptoms rapidly resolved, serial EEG recordings noted delta-wave slowing over the right hemisphere. MRI follow-up investigations after 4 months and 1 year revealed a significant atrophy of the right cortex including hippocampal sclerosis. In addition to that, FDG-PET demonstrated a right-hemispheric hypometabolism, and a decreased perfusion (-20%) of the right hemisphere was shown by ECD-SPECT. In follow-up investigations the boy's neurological status and EEG were unremarkable, and he remains well without evidence for convulsive seizures.
Conclusions: This case report underlines the variability of morphological changes after complicated febrile seizures. Interestingly, our patient demonstrated an unusually short interval for the development of cortical hemiatrophy. To differentiate these neuroimaging findings from Rasmussen encephalitis, serial EEG-recordings and FDG-PET investigations are helpful.
