SECONDARY EPILEPTOGENESIS IN PATIENTS WITH LOCALIZATION RELATED EPILEPSY SECONDARY TO HISTOPATHOLOGICALLY PROVEN CORTICAL DYSPLASIAS

Objectives: The cortical dysplasias are intrinsically epileptogenic and secondary epileptogenesis may alter surgical prognosis. We sought to determine the spatial and temporal profile of secondary epileptogenesis and identify risk factors for secondary epileptogenesis.

Methods: We retrospectively studied 34 children with intractable localization related epilepsy with histopathological confirmed cortical dysplasia. We reviewed their seizure semiology, MRI, serial EEG/VEEG and MEG findings on presurgical evaluation. We correlated demographic variables and histopathology with surgical outcomes according to Engel. We defined secondary epileptogenesis based on a new ictal onset or remote and independent interictal discharges on subsequent VEEG, and/or a new cluster or scatter on subsequent MEG studies.

Results: We found secondary epileptogenesis in 74% (25/34) of our patients most commonly in the frontal lobe. A=5 year seizure history had an attributable risk of 56% of secondary epileptogenesis. Age at seizure onset, number of AEDs, age at surgery and grades of dysplasia did not constitute significant risk factors.

Conclusion: Secondary epileptogenesis did not necessarily predict a poor surgical outcome with high and stringent concordance on presurgical evaluation. These findings lend strong clinical evidence to the phenomenon of kindling and may have implications on the timing of epilepsy surgery in cortical dysplasias.