Analysis of occipital lobe activation during functional MRI in patients with open-angle glaucoma and correlation with clinical results

Objective To evaluate the activation of the visual cortex in patients with primary open-angle glaucoma (POAG) and to explore whether the neuronal activity corresponds with retinal nerve fiber layer (RNFL) and cup-to-disc (C/D) values. Methods Twenty-five patients and 25 gender-and age-matched healthy volunteers were studied.Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-f MRI) and three-dimensional brain volume imaging (3D BRAVO) sequences were obtained using 3 T MR imaging system.A full-screen black-white shift checkerboard was used for visual stimulus during the f MRIexperiment and was performed on each eye of all subjects using a visual-acoustical system.All acquired data were postprocessed and analyzed by statistical parametric mapping (SPM).After analysis,individual activated mapping,intra-group mean activated mapping,and inter-group variant mapping were observed.The voxel number,intensity,and Montreal Neurological Institute (MNI) coordinate of the activated clusters were recorded.The Xjviewer software was utilized to obtain activated voxel numbers in occipital lobe.A Pearson correlated test was performed to test the correlation between the number of activated voxels and RNFL,C/D and Hodapp-Anderson-Parrish (HAP) clinical stage. Results Intra-group mean activated mappings of both patients and volunteers showed obvious activation in bilateral occipital lobes.As compared with healthy volunteers,the POAG patients exhibited statistically significantly decreased activation in bilateral occipital lobes,left hippocampus,and left cerebellum,along with lower mean RNFL[ (71.56±21.54) μm versus (111.88±9.96) μm] and higher C/D values (0.71±0.18 versus 0.36±0.08; tvalue was respectively-10.901 and 11.643,P 0.05). Conclusions f MRI demonstrated differences in visual cortex activation in POAG patients relative to healthy volunteers,suggesting it might be a promising complementary method for diagnosing glaucoma.However,f MRI findings did not correlate with POAG extent,as measured by RNFL and C/ D values.Ophthalmological examination remains to play an important role in the evaluation of openangle glaucoma. Key words: Glaucoma; Magnetic resonance imaging; Photic stimulus