The Role of Histopathologic Subtype in the Setting of Hippocampal Sclerosis-Associated Mesial Temporal Lobe Epilepsy

Publication date: Available online 18 March 2017
Source:Human Pathology
Author(s): Jordan M. Gales, Lara Jehi, Amy Nowacki, Richard A. Prayson
Hippocampal sclerosis (HS) and focal cortical dysplasia (FCD) are among the most common neuropathological findings in those undergoing surgery for refractory mesial temporal lobe epilepsy (MTLE). Existing data regarding differences among the most recent International League Against Epilepsy (ILAE) HS subtypes remains limited. This study sought to characterize the roles of HS subtype and coexistent FCD. Epilepsy surgery pathologic specimens in 307 cases of temporal lobe epilepsy with HS were reviewed (mean age ± SD, 37 ± 15 years, 56% women). HS and coexistent FCD were classified according to ILAE guidelines. Medical records were reviewed for data on seizure recurrence and seizure burden (clinical follow-up mean duration ± SD, 5±4 years). Cases of typical HS (ILAE type I) predominated [ILAE type Ia: 41%, Ib: 47%, II: 11%, III: 0.7%]. The HS subtypes shared similar demographic and etiologic characteristics, as well as associated pathology and post-operative seizure outcomes. Individuals with type Ib HS were more likely to remain seizure free at long term follow-up when compared to other subtypes, and they had a later age of seizure onset. Two hundred-forty-three cases (79%) demonstrated FCD within the adjacent temporal lobe. Its presence was associated with a significantly decreased risk of seizure recurrence (p=.02). When present, FCD was predominantly Type I (98%). HS subtype does not appear to affect epilepsy surgery outcomes, despite some clinical differences between the subgroups. FCD is often observed in association with HS in MTLE; the finding of FCD was associated with better post-operative outcomes.



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