| Purpose: To prospectively investigate optic nerve and optic radiation neurodegeneration in patients with primary open-angle glaucoma (POAG) utilizing MR diffusion tensor imaging (DTI) and determine whether DTI-derived parameters correlate with disease severity. Materials and Methods: The study was approved by the institutional review board. 24 patients with known POAG and 24 age-matched healthy volunteers were examined. Disease severity was clinically assessed with use of a six-stage system based on static threshold visual field parameters. All subject underwent imaging on a 3T MR system utilizing a DTI sequence(TR/TE 13000/68.9 msec, slice thickness 2 mm without interslice gaps, matrix 128×128, field of view 240 mm×240 mm, number of signal averages (NEX) 2, maximal b value 800 sec/mm2 along 30 directions, scan time 13′39〞)and a BRAVO sequence to provide a structural view for DT imaging(TR/TE/TI 6.8/3.5/380 msec, slice thickness 1 mm without interslice gaps, matrix 256×256, field of view 240 mm×240 mm, in-plane resolution 1mm, NEX 1, bandwidth 41.67 Hz, flip angle 15°, scan time 2′43〞). All the original data were processed by tract-based spatial statistical(TBSS) analysis, a part of FMRIB soft library(FSL). Mean diffusivity (MD) and fractional anisotropy (FA) maps of dorsal visual pathway in the POAG patients were compared with the healthy controls and the correlation between the POAG group and the clinical stages were further made.Results: The dorsal visual pathway of patients with glaucoma, as compared with control subjects, had significantly higher MD of POAG group((1.24±0.41)×10-3 mm2/sec versus control group (1.11±0.31)×10-3 mm2/sec, p<10-3)and significantly lower FA(mean value of POAG group 0.46±0.13 versus control group 0.56±0.10, p<10-3). The mean MD values for the dorsal visual pathway were positively correlated with glaucoma stages (r=0.597,p<10-3) while the mean FA values were negatively correlated with glaucoma stages (r=-0.793,p<10-3).Conclusion: Glaucoma is a neurologic degenerative disease that affects dorsal visual pathway. Our findings that the value of DTI parameters (MD and FA ) in the patient group is different from that in control group and the changes of parameters in dorsal visual pathway are in correlation with glaucoma severity suggest that these parameters could serve as complementary indicators of disease severity. Purpose: To analyse functional connectivity (FC) of the visual cortex in patients with primary open-angle glaucoma (POAG) utilizing resting-state functional MRI.Materials and Methods: 22 patients with known glaucoma and 23 age-matched healthy volunteers were included in this IRB-approved study. All subjects underwent imaging on a 3T MR system utilizing resting-state blood oxygenation level dependent (BOLD) sequence(TR/TE 2000/30 msec, Matrix 64×64, FOV 240 mm×240 mm, slice thickness 3 mm with interslice gaps 1 mm,total slices 33, scan time 8′)and three-dimension Brain Volume imaging (3D BRAVO) sequence(TR/TE/TI 6/2/380 msec, slice thickness 1.2 mm without interslice gaps, matrix 192×192, field of view 240 mm×240 mm, NEX 1, flip angle 15°, bandwidth 41.67Hz, scan time 1′40″). The data post-processing was executed by domestic software(data processing assistant for resting-state fMRI, DPARSF) through follow steps: converting data format, removing first 10 time points, slice timeing, head motion correction, normalization, smoothing, removing linear trend, filtering, removing effect of nuisance covariates and FC analysis. The averaged time course was obtained from the Brodmann area(BA) 17/18/19, as regions of interest(ROI), which was performed in a voxel-wise way to generate the FC map(t value map) to show the FC between the ROI and the full brain voxel by voxel. The averaged time course of ROI(BA17/18/19/7) was then analysed in a ROI-wise way to show the correlations among these ROIs and the correlation coefficient r value was converted into z score by Fisher's r-to-z transform.Results: As compared with control group, the POAG group showed increased functional connectivity between the primary visual cortex (BA17) and the follow areas, including left cerebellum, bilateral limbic gyrus, medial prefrontal cortex and right inferior frontal gyrus (p<0.05). Some regions, however, showed decreased connectivity, such as right inferior temporal gyrus, left medial occipital lobe and bilateral precentral gyrus (p<0.05). Significant greater connectivity between the senior visual cortex (BA18/19) and some brain region (right inferior frontal gyrus, medial prefrontal cortex, right medial temporal gyrus and bilateral limbic gyrus) while a decreased connectivity between BA18/19 and these region (bilateral medial frontal gyrus, right inferior parietal lobule, right frontal gyrus and right cerebellum) was observed in POAG group compared with control group (p<0.05). The correlation between BA17 and BA19 was found significantly weaker in POAG group than that in control group (p<0.05).Conclusion: This is the first study to employ resting-state functional magnetic resonance imaging to investigate the functional connectivity of the visual cortex in patients with POAG. These findings suggest that patients with POAG bear functional connectivity changes between visual cortex and some relative visual area. Further, we find disrupted connectivity between primary visual area and senior visual area in patients with POAG. Purpose: To value the application of blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) on visual stimulus in patients with primary open-angle glaucoma (POAG) and to explore whether the result of BOLD-fMRI is varied with that of ophthalmological examination consistently.Materials and methods: 25 patients and 25 age-matched healthy volunteers were included in the study. 27 eyes of patients and 49 eyes of controls were eventually put into analysis. BOLD-fMRI and three-dimension brain volume imaging (3D BRAVO) sequences were scanned using 3 tesla magnetic resonance (3T MR) machine. Full-screen black-white shift checkboard used in the visual stimulus block design of fMRI experiment were executed on each eye of all subjects by special visual-acoustical system. All the data were firstly processed by statistical parametric mapping (SPM) via head motion correction, coregistering, normalization and smoothing and then put into data analysis. After the last step was finished, of which the statistical threshold was set as follow: p value was 0.05 in FWE correction and the minimum valid voxel was 10, several mappings including individual activated mapping, intra-group mean activated mapping and inter-group variant mapping were observed and some indicators such as voxel number, intensity and Montreal Neurological Institute (MNI) coordinate of the activated clusters showed on the mappings were recorded. In patient group, Xjview software was applied to obtain the activated voxel number of visual cortex in each patient and the retinal nerve fiber layer (RNFL), cup/disc (C/D) and glaucoma stage by Hodapp-Anderson-Parrish (HAP) system was recorded by ophthalmologist. Spearman non-parametric correlation method was used to analyse the correlation between BOLD-fMRI and clinical result.Results: Both intra-group mean activated mappings of patients and control group showed obvious activation in bilateral lingual gyrus in occipital lobe. As compared with control group, significantly different activation as well as lower RNFL and higher C/D were observed in POAG group (p<0.05). The value of RNFL is varied with C/D consistently (r=0.7,p<10-3) and both the value of RNFL and C/D was correlated with HAP glaucoma stage (r=-0.837, r=0.624 respectively). However, there were no correlation between the activated voxel number of visual cortex in occipital lobe and the value of RNFL or C/D in patients with POAG ( p>0.05).Conclusion: Evaluating glaucoma severity, so far, as we know, is mainly fulfilled by or to some degree depended on ophthalmological examination. In our study, the finding that fMRI shows different activation in the visual area in patients with POAG suggesting it maybe a promising complementary method in diagnosis of glaucoma. However, fMRI could not serve as a substitute method for the ophthalmological examination in evaluation of the disease severity since the insufficient proof was given. There is no correlation between BOLD-fMRI and clinical examination result showed in our study. |
PDF Full Text Request