HUMAN FASCIA-DENTATA ANATOMY AND HIPPOCAMPAL NEURON DENSITIES DIFFER DEPENDING ON THE EPILEPTIC SYNDROME AND AGE AT FIRST SEIZURE

This study determined fascia dentata anatomy and hippocampal neuron de nsities in patients with different epileptic syndromes. Based on presu rgical data, patients were classified into: (a) pediatric patients (n= 19); (b) temporal mass lesion cases (n=14); and (c) hippocampal sclero sis patients (n=31). Surgically removed hippocampi and autopsies (n=34 ) were studied for: (a) hippocampal neuron densities; (b) stratum gran ulosum (SG) widths and lengths; and (c) hilar areas. The number of gra nule cells and hilar neurons per tissue section were estimated from th e neuron densities and fascia dentata area measurements. Results showe d that compared with autopsies (p<0.05): (a) pediatric patients had si milar SG and hilar areas; granule cell density was lower (but not hila r neuron density); and the estimated number of granule cells was lower (but not the number of hilar neurons); (b) the widths of SG and hilar areas were greater in mass lesion cases; the density of granule cells and hilar neurons was lower; and the total estimated numbers of granu le cells and hilar neurons were similar to those of the autopsies; and (c) hippocampal sclerosis patients had wider, yet shorter SG; hilar a reas were smaller; granule cell and hilar densities were lower; and th e total estimated numbers of granule cells and hilar neurons were lowe r than those of the autopsy cases. The duration of the seizures did no t correlate with lower fascia dentata neuron densities or estimates of total granule cell and hilar neurons. Furthermore, greater SG widths correlated with lower hilar and CA4 neuron densities, but not with age at first seizure or duration of epilepsy. These results indicate that the size of the fascia dentata SG and hilus along with hippocampal ne uron densities differ between surgical patients with different epilept ic syndromes, and a wider SG was associated with a lower density of en d folium neurons. These findings support the hypothesis that hippocamp al sclerosis and granule cell dispersion are not the consequence of re petitive seizures beginning at an early developmental age, but seem to differ depending on the type of epileptic syndrome.