BILATERAL REDUCTIONS IN HIPPOCAMPAL VOLUME IN ADULTS WITH EPILEPSY AND A HISTORY OF FEBRILE SEIZURES

Objectives-To examine the degree and frequency of reductions in hippoc ampal volume in patients with temporal lobe epilepsy with and without a history of febrile seizures. Methods-In vivo measures of hippocampal volume were computed from three dimensional gradient echo (FLASH) ima ges in 44 patients undergoing comprehensive evaluations for epilepsy s urgery. Twenty one patients (48%) reported a history of febrile seizur es. The volumes from these patients were compared with those from 23 p atients without a history of febrile seizures and 34 healthy controls. Results-The febrile seizure group had significant reductions in volum e, both ipsilateral (30% decrease) and contralateral (15% decrease), t o the EEG seizure focus. Twelve of 18 patients with febrile seizures e xhibited clinically significant ipsilateral volume reductions, defined as volumes falling 2 SD below the mean obtained from the control samp le. Only four of 19 patients without febrile seizures exhibited this d egree of reduction. No significant correlations were found between sei zure variables (for example, duration of epilepsy, seizure frequency) and ipsilateral reductions in volume. However, a significant inverse c orrelation (r=-0.45, P<0.05) between seizure frequency and the volume of the hippocampus contralateral to the seizure focus was found in the febrile seizure group. Conclusion-These results suggest that a histor y of febrile seizures is associated with the finding of a smaller hipp ocampus on the side ipsilateral to the subsequent temporal lobe focus whereas chronic factors seem to be be related to pathology contralater al to the seizure focus.