Hippocampal damage and the onset of epilepsy

Abstract

To the Editor: In their interesting study, Kalviainen et al. investigated the hippocampus of 64 patients with temporal lobe epilepsy (TLE) by MRI.1 They divided the subjects into three groups: chronic drug-resistant patients (CDRPs) with large number of seizures, well-controlled patients (WCPs) with rare seizures, and newly diagnosed patients (NDPs). The authors found that CDRPs had significantly smaller hippocampus with longer T2 relaxation time on the side of spike focus than healthy controls. Neither NDPs nor WCPs showed significant hippocampal atrophy compared with control subjects. The authors’ interpretation is that recurrent seizures may cause hippocampal damage. In our opinion, this conclusion is unconfirmed because the results may have been caused by other factors. The authors did not consider many studies that found age dependency of development of hippocampal damage in epilepsy. Re-evaluating the data of Kalviainen et al.,1 we found significant differences regarding mean age and age at onset of epilepsy. WCPs were 10 years older on average than CDRPs. This difference is statistically significant (see table 1) and was not mentioned in the original article. Because median duration of epilepsy was practically equal, we suppose that in WCPs …