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fNIRS-VFT is a complementary tool to 18F-FDG PET in presurgical evaluation of drug-resistant epilepsy: an exploratory
Shuting Hong1,2, Huiqin Xiao3, Chengjun Li1,3
1Department of Neurosurgery, the First Affiliated Hospital, Fujian Medical University, Fuzhou, 350005, China.
Background:
Accurate presurgical localization of the epileptogenic zone (EZ) and preservation of postoperative cognitive function are two critical but often competing goals in epilepsy surgery for drug-resistant epilepsy (DRE). This study aimed to (1) evaluate the complementary value of functional near-infrared spectroscopy during a verbal fluency task (fNIRS-VFT) alongside interictal 18F-FDG PET for presurgical EZ localization; and (2) explore whether task-based fNIRS functional connectivity is associated with postoperative verbal memory decline.
Methods:
We retrospectively included patients with DRE who underwent epilepsy surgery between December 2022 and December 2023 and completed both interictal PET and fNIRS-VFT assessments. All analyses in this study were descriptive, and no robust inferential statistical testing was performed. For the localization outcome, concordance between PET hypometabolism and fNIRS-VFT hypoactivation was analyzed in patients who achieved seizure freedom two years after surgery. For the memory outcome, post- vs. pre-operation change of task-based fNIRS functional connectivity was compared between patients with and without clinically significant postoperative verbal memory decline (≥ 4 point reduction on Auditory Verbal Learning Test delayed recall).
Results:
Twenty-eight patients were included in this study. Among 20 patients achieving seizure freedom, PET demonstrated concordant lateralization with the EZ in 14 cases (70%), including 11 with accurate localization; fNIRS-VFT showed concordant lateralization in 9 patients (45%), with 4 accurate localizations including one case in whom PET failed to lateralize the EZ, indicating the complementary value of fNIRS-VFT. Among 19 patients with complete memory data, four showed significant postoperative decline. These patients exhibited more pronounced alterations in task-related functional connectivity, particularly involving frontopolar, dorsolateral prefrontal, premotor, and temporal regions.
Conclusions:
In this exploratory, descriptive analysis, interictal 18F-FDG PET showed higher concordance with lateralization of surgical areas compared with fNIRS-VFT among patients with DRE. Nevertheless, fNIRS may provide complementary information for cases with inconclusive PET findings. Additionally, changes of task-based fNIRS connectivity may be correlated with postoperative verbal memory alterations. These preliminary findings suggest that fNIRS-VFT may provide complementary information in selected cases, which warrants validation in larger prospective cohorts.
