Hippocampal volumetry in children 6 years or younger: assessment of children with and without complex febrile seizures

Purpose: To study the relationship of complex febrile seizures (CFS) in the evolution of mesial temporal sclerosis. Methods: We studied five children 22-68 (mean 44) months old with MRI volumetry 2 days-46 months after their first CFS, and compared total hippocampal volumes and right to left hippoca mpal volume ratios to those of 11 controls, 15-83 (mean 55) months old, who had MRI for complaints which turned out to be neurologically insignificant . Results: In control children, total hippocampal volumes increased linearl y with age, while right to left hippocampal volume ratios tended to decreas e with age. In children with CFS total hippocampal volumes tended to be sma ller than in controls. Right to left ratios were greater than 1 in all five children with CFS compared to seven of 11 controls. Hippocampal asymmetry was noted in only one child, with the right to left volume ratio exceeding two standard deviations from the control mean. The MRI of this child also d emonstrated a subarachnoid cyst in the left frontocentral region, ipsilater al to the smaller hippocampus. Visual inspection of the remaining patients revealed no definite structural cortical abnormalities. None of the childre n developed subsequent afebrile seizures during the brief follow-up period. Conclusions: Hippocampal volumetry in controls revealed a linear increase in total hippocampal volumes and a statistically nonsignificant trend towar d reduced right larger than left hippocampal ratios between 17 and 83 month s old. The tendency for smaller total hippocampal volumes and larger right to left hippocampal volume ratios in children with CFS compared to controls could suggest a developmental abnormality, injury during CFS, or be age-re lated. The significant hippocampal asymmetry in a single child with CFS sug gests that age may not be a factor in every case. Further studies are neede d to collect control data in young children as well as prospectively follow children with CFS with serial imaging to better understand the relationshi p between CFS and the evolution of hippocampal atrophy. (C) 1999 Elsevier S cience B.V. All rights reserved.