Commentary on long‐term seizure outcome in 211 patients with focal cortical dysplasia

To the Editors: We have read with great interest the paper by Fauser et al.,1 titled “Long-term seizure outcome in 211 patients with focal cortical dysplasia. ” This study is a valuable effort to identify the predictors of long-term seizure control in epilepsy surgery for focal cortical dysplasia (FCD). As the authors stated, FCD represents a common architectural or cytoarchitectural cortical disorder underlying pharmacoresistant epilepsy. We agree with the authors about the importance in epilepsy surgery of both identifying the factors predicting seizure outcome and relating seizure outcome to histopathologic diagnosis.2-9 The value of this study is represented by the large number of enrolled patients and the relationship between seizure outcome and FCD types. However, it is our opinion that considering FCD independently of the site involved (left or right hemisphere, critical cerebral areas) and of the different surgical approaches (ranging from lesionectomy to multilobar lobectomy) represents a notable bias. We think that this methodology likely may have contributed to masking of some important differences among FCD types I, II, and IIIa, thereby preventing the acquisition of statistically significant differences regarding seizure freedom. In our temporal lobe epilepsy surgery experience, the most common pathology in adult patients has been FCD type IIIa.3, 7 Furthermore, according to the literature,9, 10 the patients with hippocampal sclerosis (HS) associated with FCD type I (now classified as FCD IIIa) show a seizure outcome similar to that of patients with isolated HS (84% Engel class I vs. 82%) and better than patients with isolated FCD type I (63% Engel class I).3, 7, 10-12 Our results indicate also that cases of associated FCD type II are not as rare as previously reported, such as for instance, the association between FCD type II and other structural abnormalities, namely, HS or epilepsy-associated tumors (EATs).3, 7, 13 On the contrary, the International League Against Epilepsy (ILAE) Task Force FCD Classification2 reported the combination of these atypical findings as a rare association (dual pathology [FCD type II–HS] and double pathology [FCD type II–EAT]). However, we found 18 “atypical” cases of 80 FCD cases (20.5% of all FCD cases and 26.6% of FCD associated with a principal lesion): 10 cases of FCD II-HS and 8 cases of FCD II-EAT. Regarding the seizures outcome results in these “Atypical” cases (i.e., FCD type II + HS and FCD type II + EAT): 5 of 10 patients (50%) with FCD type II + HS were in Engle class Ia, whereas 6 of 8 patients (75%) with FCD type II + EAT were completely seizure free.7 These aspects may prove a useful parameter for more precise histopathologic classification that may help to clarify the relationship with seizure outcome and the implications for pathogenetic epileptogenic mechanisms. Finally, a methodologic approach utilized for other brain pathologies, such as cerebral tumor or vascular lesions, will be unavoidable due to the continuous remarkable advances in pathologic knowledge of underlying epilepsy lesions. This unifying methodologic approach aims to relate the surgical results to the precise type of pathology, the site of the lesion, and the surgical strategy utilized. We think that this approach will help epilepsy surgery to come out of a long-lasting status of indeterminateness and promote a greater spread and application of the practice. We have no conflict of interest in publishing this letter. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.