Focal Cortical Dysplasia IIb in Treatment-Resistant Epilepsy: a 15-Year single-surgeon experience

Introduction: Focal cortical dysplasia (FCD) is a common cause of treatment-resistant epilepsy. While MRI is able to identify FCD, MRI-negative FCD cases are common. Hence, lesion boundary determination can be challenging. Seizure-freedom rates following surgery range from 61%-87%. This study describes a single-surgeon experience, exploring patient and disease characteristics, as well clinical outcomes.

Methods: We identified patients diagnosed with FCD-IIb who underwent epilepsy surgery over a 15-year period. The study evaluates surgical approaches, demographics, clinical presentations, MRI findings and electroencephalographic characteristics. Both neuropsychological assessments and seizure-outcomes were assessed as our main outcomes of interest.

Results: In our study, we identified thirty-six patients with treatment-resistant FCD-IIb. The median ages at seizure onset and at surgery were 5.5 years (IQR=1.2-11.7), and 24 years (IQR=17.2-33.7), respectively. Eight cases presented with focal seizures, three with generalized seizures, five with focal with secondary generalization, and twenty displayed a mixed pattern. Nineteen underwent invasive monitoring through sEEG or SDE. 10 patients were MRI-negative for FCD, while 26 were MRI-positive. Surgical interventions included: 15 patients had partial or complete lobectomies, 18 lesionectomies or topectomies, and 3 received a combined approach. Post-resection electrocorticography revealed sparse or frequent spikes in 12 patients. Nine patients developed postoperative new-onset neurological deficits. At 1-year follow-up, 100% of patients achieved a ≥50% seizure reduction and 54% achieved ILAE Class 1. There was no postoperative neuropsychological deterioration as measured by VIQ, PIQ, and FSIQ scores (p-values= 0.703, 0.342, and 0.535, respectively). Outcomes were similar regardless of MRI characteristics.

Conclusion : FCD-IIb epilepsy can be successfully managed with surgery to improve clinical outcomes. Notably, a significant proportion of patients were MRI-negative, highlighting MRI might not identify some cases. A majority of patients achieved substantial seizure reduction without postoperative cognitive decline. FCD-IIb may be appropriately managed with individualized approaches.