Mesial temporal lobe epilepsy: clinical and neuropathologic findings of familial and sporadic forms

Purpose: To evaluate the clinical and hippocampal histological features of patients with mesial temporal lobe epilepsy (MTLE) in both familial (FMTLE) and sporadic (SMTLE) forms.
Methods: Patients with FMTLE (n = 20) and SMTLE (n = 39) who underwent surgical treatment for refractory seizures were studied at the University of São Paulo School of Medicine at Ribeirão Preto. FMTLE was defined when at least two individuals in a family had clinical diagnosis of MTLE. Hippocampi from all patients were processed for Nissl/HE and Timm's stainings. Both groups were compared for clinical variables, hippocampal cell densities, and intensity of supragranular mossy fiber staining.
Results: There were no significant differences between FMTLE and SMTLE groups in the following: age at the surgery, age of first usual epileptic seizure, history of initial precipitating injury (IPI), age of IPI, latent period, ictal and interictal video-EEG patterns, presence of hippocampal atrophy and signal changes at MRI, and postoperative outcome. In addition, no differences were found in cell densities in hippocampal cornu ammonis subfields (CA1, CA2, CA3, CA4), fascia dentata, polymorphic region, subiculum, prosubiculum, and presubiculum. However, patients with SMTLE had greater intensity of mossy fiber Timm's staining in the fascia dentata-inner molecular layer (p< 0.05).
Discussion: Patients with intractable FMTLE present a clinical profile and most histological findings comparable to patients with SMTLE. Interestingly, mossy fiber sprouting was less pronounced in patients with FMTLE, suggesting that, when compared to SMTLE, patients with FMTLE respond differently to plastic changes plausibly induced by cell loss, neuronal deafferentation, or epileptic seizures.