Pathology-Based Approach to Seizure Outcome after Surgery for Pharmacoresistant Medial Temporal Lobe Epilepsy

BACKGROUNDS: Hippocampal sclerosis (HS) is the most common cause of drug-resistant medial temporal lobe epilepsy (MTLE). Structural abnormalities such as HS, granule cell pathology (GCP) and focal cortical dysplasia (FCD), have been histopathologically classified possibly allowing more accurate prognostic seizure and neuropsychological outcome assessment. We correlated seizure outcome with comprehensive temporal lobe pathological findings, identified according to the most recent classification systems of HS, GCP and FCD. METHODS: All the 83 patients submitted to anterior temporal lobectomy (ATL) for drug-resistant MTLE and with a proven diagnosis of HS between April 2001 and May 2014 were collected. Patients were divided in two main groups: 1) Isolated HS with/without GCP (HS +/- GCP) 2) HS associated with FCD with/without GCP (HS+FCD +/- GCP). Patients were followed up at least 1 year and seizure outcome was reported in accordance with Engel classification. RESULTS: Group I: HS +/- GCP: Statistical analysis confirmed a better outcome in HS + GCP patients than in HS-noGCP (p < 0,05). Moreover, a better outcome for the patients affected by GCP type I was observed (p < 0,05). Group II: HS+FCD +/- GCP: Patients with HS variant type I presented a better seizure outcome than the patients with HS type II (Engel class IA HS type I vs. type II: 69% vs. 40%). CONCLUSIONS: A pathology based approach to epilepsy surgery might improve the interpretation of the results, could predict which cases will enjoy a better seizure outcome and could help to the comprehension of the causes of failures