Identifying the epileptogenic zone by 18F-FDG PET/MRI in drug-resistant epilepsy with focal cortical dysplasia type IIIa.

OBJECTIVE: Focal cortical dysplasia (FCD) type IIIa, distinct from isolated FCD in drug-resistant epilepsy, is typically confirmed via postoperative histopathology. This study aimed to evaluate the diagnostic utility of preoperative noninvasive 18F-fludeoxyglucose (FDG) PET/MRI co-registration in localizing the epileptogenic zone (EZ) in FCD type IIIa.

METHODS: We performed a retrospective study that included 60 patients with FCD type IIIa who underwent resection for drug-resistant epilepsy. The sensitivity of each modality for localizing the EZ was calculated, with invasive stereoelectroencephalography (SEEG) as a reference. Diagnostic accuracy and value of each modality were further assessed with respect to SEEG and postoperative outcomes for all patients and MRI negative/doubtful patients.

RESULTS: We analyzed the diagnostic value of the different non-invasive diagnostic techniques with respect to concordance with SEEG findings and postsurgical seizure outcomes. For all included patients, 18F-FDG PET/MRI showed the highest sensitivity (75.7 %) for localizing the EZ across all modalities. We also found that 18F-FDG PET/MRI demonstrated the best accuracy and diagnostic value for localizing the EZ (60.0 %). Among MRI-doubtful/negative patients, 18F-FDG PET/MRI not only showed the highest sensitivity (79.3 %) but also achieved most promising accuracy and diagnostic value for identifying the EZ (61.7 % accuracy) across all modalities.

SIGNIFICANCE: 18F-FDG PET/MRI coregistration appears to be overwhelmingly rewarding in affording localization of EZ for patients with FCD type IIIa. This technique is potentially valuable as a noninvasive method to identify the EZ in patients with drug-resistant epilepsy due to FCD type IIIa, especially for MRI-negative/doubtful patients.