Hippocampal chemical anatomy in pediatric and adolescent patients with hippocampal or extrahippocampal epilepsy.

We determined whether age or seizure types were associated with hippocampal neuron loss, mossy fiber (MF) and GABAergic synaptic reorganizations or postsynaptic receptor densities. Children and adolescents were grouped into: (1) nonhippocampal sclerosis (non-HS; n = 11) and (2) hippocampal sclerosis (HS; n = 11). The most important results showed that: (1) regardless of the etiology of the seizures, there were greater cell losses in Ammon's horn with older ages in years; in the non-HS group, cell losses were greater with the older ages or with longer epilepsy durations; however, in the HS patients, the cell losses were not related to the patients' ages or epilepsy durations; (2) in both HS and non-HS, CA1 had greater cell losses than CA4; (3) in HS, CA1 and CA4 had greater cell losses than those in non-HS; (4) in non-HS, MF sprouting was greater with ages or with longer epilepsy durations; by contrast, in HS, MF sprouting was not related to the patients' age or epilepsy duration; (5) densities for AMPA GluR1, GABA-Abeta and for GABA axonal terminals were positively increased with age. These findings support the hypothesis that hippocampal cell losses and aberrant synaptic reorganizations are greater in the hippocampi of adolescents than in children, even for non-HS pathologies.