Evaluation of MRI post-processing methods combined with PET in detecting focal cortical dysplasia lesions for patients with MRI-negative epilepsy.

OBJECTIVE: Accurate detection of focal cortical dysplasia (FCD) through magnetic resonance imaging (MRI) plays a pivotal role in the preoperative assessment of epilepsy. The integration of multimodal imaging has demonstrated substantial value in both diagnosing FCD and devising effective surgical strategies. This study aimed to enhance MRI post-processing by incorporating positron emission tomography (PET) analysis. We sought to compare the diagnostic efficacy of diverse image post-processing methodologies in patients presenting MRI-negative FCD. METHODS: In this retrospective investigation, we assembled a cohort of patients with negative preoperative MRI results. T1-weighted volumetric sequences were subjected to morphometric analysis program (MAP) and composite parametric map (CPM) post-processing techniques. We independently co-registered images derived from various methods with PET scans. The alignment was subsequently evaluated, and its correlation was correlated with postoperative seizure outcomes. RESULTS: A total of 41 patients were enrolled in the study. In the PET-MAP(p = 0.0189) and PET-CPM(p = 0.00041) groups, compared with the non-overlap group, the overlap group significantly associated with better postoperative outcomes. In PET(p = 0.234), CPM(p = 0.686) and MAP(p = 0.672), there is no statistical significance between overlap and seizure-free outcomes. The sensitivity of using the CPM alone outperformed the MAP (0.65 vs 0.46). The use of PET-CPM demonstrated superior sensitivity (0.96), positive predictive value (0.83), and negative predictive value (0.91), whereas the MAP displayed superior specificity (0.71). CONCLUSIONS: Our findings suggested a superiority in sensitivity of CPM in detecting potential FCD lesions compared to MAP, especially when it is used in combination with PET for diagnosis of MRI-negative epilepsy patients. Moreover, we confirmed the superiority of synergizing metabolic imaging (PET) with quantitative maps derived from structural imaging (MAP or CPM) to enhance the identification of subtle epileptogenic zones (EZs). This study serves to illuminate the potential of integrated multimodal techniques in advancing our capability to pinpoint elusive pathological features in epilepsy cases.

Diffusion spectrum imaging based semi-automatic optic radiation tractography for vision preservation in SEEG-guided radiofrequency thermocoagulation.

OBJECTIVE: To assess the efficacy and safety of stereoelectroencephalography (SEEG)-guided radiofrequency thermocoagulation (RFTC), using diffusion spectrum imaging (DSI) tractography to preoperatively delineate the optic radiation (OR) and reduce the risk of visual field defects (VFDs) where the epileptogenic zones (EZs) are located in or close to the eloquent visual areas. METHODS: We prospectively followed up twenty-four consecutive patients (12 males and 12 females) who underwent SEEG-guided RFTC in or near the OR pathway. A distance of ≥ 3.5 mm away from the OR on the targeted electrodes contacts that exhibited relevant ictal onset patterns, IEDs and EES during SEEG recordings, was required as our selection criterion prior to performing RFTC, enough to theoretically prevent VFDs. Using default tracking parameters, the optic radiation was tracked semi-automatically in DSI-studio. RESULTS: There were 12 male and 12 female patients ranging in age from 6 to 57 years, with follow-up period ranging from 6 to 37 months. Nineteen patients responded to RFTC (R+, 79.16 %), and 5 patients did not benefit from RFTC (R-, 20.83 %). The preoperative application of DSI semi-automatic based OR tractography was successful in the protection of the OR in all 24 patients. Three patients experienced a neurologic deficit following RFTC, and five patients had a partial quadrant visual field deficit prior to surgery that did not worsen, and none of the remaining nineteen patients had a quadrant visual field deficit. CONCLUSION: Our study validates the safety and efficacy of SEEG-RFTC as a viable therapeutic approach for epileptic foci situated in or adjacent to the visual eloquent regions. We demonstrate that DSI-based tractography offers superior precision in delineating the OR compared to DTI. We establish that implementing a criterion of a minimum distance of ≥ 3.5 mm in radius from the OR on the targeted electrode contacts prior to conducting RFTC can effectively mitigate the risk of VFDs.