WASHINGTON, DC—Childhood convulsive status epilepticus (CSE) may not damage the hippocampus unless it occurs years after the causative event, according to a study presented at the 67th Annual Meeting of the American Epilepsy Society. Prolonged febrile seizures also may not impair hippocampal growth in children.
Neurologists have long hypothesized that prolonged febrile seizures, the most common form of childhood CSE, cause mesial temporal sclerosis (MTS), which entails a loss of neurons and scarring of the hippocampus. Whether prolonged convulsions lead to long-term damage to the hippocampus or to MTS is uncertain.
A team of investigators from the United Kingdom and the United States used three-dimensional MRI imaging to measure hippocampal volume in 144 children. The cohort included 74 patients with seizures classified into four subgroups: prolonged febrile seizure, acute symptomatic (CSE at time of causative event such as meningitis or head injury), remote symptomatic (CSE months to years after causative event), and idiopathic or unclassified. The cohort also included 70 healthy controls.
Each hippocampal slice was measured independently by two investigators blind to clinical details. The hippocampal volume was measured on each side, and right–left asymmetry was calculated using asymmetry index. Volumetric images were taken at a mean follow up of 8.5 years (range 6.3 to 10 years) after the convulsive episode. The investigators also compared these measures across all patient groups.
The researchers found no significant corrected volumetric differences between the groups, except for the subgroup of children with remote symptomatic CSE, whose mean corrected hippocampal volume was 553 mm3 lower than that of controls. Asymmetry of the hippocampal structure also was significantly greater in the remote symptomatic subgroup, compared with the other groups. The investigators found no significant differences in asymmetry or corrected volume between the other CSE groups and healthy controls.
“On group analysis, hippocampal growth in children who had prolonged febrile seizures, acute symptomatic, and idiopathic or unclassified CSE was not impaired at a mean follow-up of 8.5 years post CSE,” said Suresh Pujar, MD, clinical research fellow in epilepsy at the Institute of Child Health, University College of London, and lead author of the study. “But children with remote symptomatic CSE have a significant reduction in hippocampal volume and increased asymmetry, compared with all the other groups in our study.”
The results of the study suggest that prolonged seizures, whether febrile or afebrile, may not have a lasting effect on hippocampal growth in children who were neurologically normal before CSE, according to the investigators.
—Erik Greb