Abstracts

Hippocampal changes in temporal lobe epilepsy include neuronal loss and glial proliferation. The majority of quantitative studies on hippocampal cells involve the neuronal population. Recent studies suggest possible participation of glial cells in epileptogenesis, but the hippocampal glial density has been rarely investigated. We studied the hippocampal glial density in surgically resected hippocampi from 192 patients, who underwent partial anterior temporal lobectomy for intractable temporal lobe epilepsy. Six-micrometer thin paraffin sections of the hippocampus were made, and Nissl and/or hematoxylin and eosin stains were done. The hippocampus was divided into four CA sectors, and glial cells (astrocytes and oligodendroglial cells) were counted in multiple consecutive 200X400 micrometer unit areas. Twenty-three age-and gender-matched postmortem cases were included for control. In the epilepsy group, every CA sector showed a moderate to marked increase in glial density (165% in CA2 to 349% in CA1, compared with the control group). There was statistically significant inverse correlation between the glial and neuronal density in each sector (p, [lt]0.001, all sectors). History of febrile seizures, absence of extra-hippocampal pathology and long duration of seizure history were positively correlated with the glial density. However, family history of seizures, gender and age at the time of surgery failed to reveal any correlation with the glial density. More interestingly, the CA1 glial density in the group with an improved clinical outcome was significantly higher than that of the non-improved group. Further, the glial density in the improved group was numerically higher in the rest of CA sectors compared with the non-improved group. The hippocampal glial density is significantly higher in temporal lobe epilepsy, and is inversely correlated with the neuronal density. Enhanced hippocampal glial density may predict a better surgical outcome, which, in turn, speaks for a role of glial cells in epileptogenesis. (Supported by 2PO1 NS039092)