Abstracts

Rationale: Focal cortical dysplasia (FCD) is the most frequent cause of drug resistant epilepsy in the pediatric population and one of the leading causes in adults. Surgical cohorts demonstrate that they are a common finding in temporal epilepsies (Martinoni et al., 2015) and that this finding lowers the surgical outcome. (Schmeiser et al., 2016). However, the data regarding the clinical and functional outcomes in various subtypes of FCD is still very limited. Our study addresses this issue by analyzing a population explored in a homogenous method both from the epileptological and the neuropsychological perspective. Methods: Between 01.2012 and 01.2018, 41 patients were operated in Rennes University Hospital for temporal lobe epilepsy and had a diagnostic of focal cortical dysplasia. The extracted tissue was analyzed and classified by our histopathology department based on the ILAE consensus. (Blumcke et al., 2011) Visual and verbal memory (Weschler Memory Scale revised) as well as language-naming (David.D et al. 1999) were evaluated by the same experienced neuropsychologist before the surgery and 6 months after. The need for intracranial explorations, the extent of the brain resection and the seizure outcome (Engel classification) were recorded in 01.2019. For statistical testing Chi square test was used for categorical data and paired T-test or Mann Whitney for normally distributed or non-normally distributed numerical. Results: 20 patients had type II A FCD, 10 with left-sided and 10 with right-sided temporal epilepsy. From the left-sided group 7 had associated hippocampal sclerosis while this was also found in 2 patients in the right-sided group. 11 benefited from an SEEG exploration. 14 had extended temporal resections including the inferior insula and half of the T1 gyrus, while 6 had standard temporal lobectomies. 16 were completely seizure free (Engel IA), 19 had a good outcome (Engel I). For the left sided group there was a significant drop in global memory of 9.2p (p=0.007), in verbal memory 16.4p (p=0.0093) and an important but not significant impairment in naming 18.7p. No significant impairment was found in right sided resections.21 patients had type III FCD (7 type III A, 9 type III B and 5 type III C). 10 benefited from an SEEG exploration. 3 patients had extended temporal resections, 5 standard lobectomies while 13 limited resections or lesionectomies. 13 were seizure free while 20 had a good outcome – Engel I. For the left sided group there is a significant drop in global memory 10.7p (p=0.047) and even plus in verbal memory 16.2p (P=0.008). No impairment in naming was found for this group – 3.7p.The statistical analysis found no significant difference between type II and III FCD in chances to be considered in need of an intracranial exploration (55% vs 48%), to be completely seizure free – Engel IA (80% vs. 67%) or to have a good outcome Engel I (both 95%). Patients with type II FCD had more chances to require extended temporal resections (70% vs. 14%, p<0.001) while patients with type III were offered more limited resections or lesionectomies (57% vs. 0%, p=0.001). Conclusions: Our study demonstrates that focal cortical dysplasia related temporal drug-resistant epilepsy has a high chance for being surgically curable. This comes with a risk of post-surgery global and verbal memory deficit when operating in the dominant hemisphere. A careful exploration must thus be proposed, often including intracranial recordings, especially to extent or to limit the resection in the dominant language and memory networks. Funding: No funding