Objective: Mesial temporal lobe epilepsy (MTLE) constitutes a heterogenic entity with different clinical histories, pathomorphological findings and varying postoperative outcome.
Method: 64 MTLE patients, scheduled for hippocampal resection were included. Initial precipitating injuries (IPI), structural and functional findings and neuropathological classification of hippocampal specimens were related to prediction of surgical outcome.
Results: Patients with severe hippocampal sclerosis (MTS Type 1b) became significantly more often completely seizure free (80% Engel Ia) compared to ca. 40% of seizure freedom in other types of MTS or in patients without hippocampal cell loss (non-MTS), irrespective of the extent of hippocampal resection. The age at IPI was found to be related to MTS variants (p<0.01) and significantly correlated to cell loss in the CA1 sector and the dentate gyrus (p < 0.05).
Presurgical magnetic resonance imaging (MRI) discriminates between MTS and non-MTS, but did not discriminate between different MTS subtypes. Most reliable predictors of MTS-type 1b were the Wada memory scores combined with interictal and ictal EEG.
Conclusions: A particular cohort of MTLE patients benefit most from surgical treatment. These patients are clinically best recognised as presenting with (1) very early IPI; (2) silent period of about 5 years (3) unequivocal unilateral EEG-localisation. (4) MRI signs for MTS, (5) Wada Test indicates contralateral memory compensation and ipsilateral reduced memory capacity. MTS type 1b, characterized by severe cell loss in all hippocampal subfields including the DG and associated with optimal postoperative seizure control was preoperatively clinically best differentiated from other MTS types by WADA memory test.