Morphological And Functional Changes Of Central Nervous System In Primary Open Angle Glaucoma By Mri

Glaucoma is the second leading cause of blindness worldwide. It is a multi-factorial, progressive and degenerative optic neuropathy characterized by loss of retinal ganglion cells (RGCs) and subsequent visual field defects in corresponding areas. Recently, more and more studies indicate that the glaucomatous damage in Primary open-angle glaucoma (POAG) not only occurred to retinal ganglion cells in the eyes, but also went across optic nerves, visual chiasm, lateral geniculate nucleus (LGN) and finally the visual cortex, the neural degenerations could be identified through the whole visual system. Most research data of the disease in this aspect are from animal experiments. Magnetic resonance imaging (MRI) technique with noninvasive, repeatable, high temporal and spatial resolution characteristics, has been widely used in fundamental researches and clinical neuroscience applications, which provides a powerful means for investigation of brain damage in POAG in vivo.Based on 3.0 Tesla high resolution MRI, from the perspective of a combination of morphology and function, morphological changes of the lateral geniculate nucleus (LGN), nerve fibers damage of the central visual pathway, brain function of resting-state changes in POAG are investigated in this study. Part 1Morphological changes of lateral geniculate nucleus in Primary open-angle glaucomaPurpose:To investigate morphological changes of the lateral geniculate nucleus (LGN) measured by magnetic resonance imaging (MRI) and to analyze the relationship with damage to the optic disc and loss of visual function in primary open-angle glaucoma (POAG) patients.Methods:25 patients with POAG (19 males and 6 females,21-54 years old) and 24 age and gender matched healthy subjects (19 males and 5 females,21-55 years old)were enrolled. On each subject, structural damage to the optic disc:cup-to-disc ratio (CDR, by NIDEK Fundus Camera), the retinal nerve fiber layer thickness (RNFLT, by Stratus Optical Coherence Tomography) and visual function (mean sensitivity, MS and mean defect, MD*, by Octopus 101 Automated Perimeter) were measured,3.0 Tesla MRI examinations of LGN were performed (3D-BRAVO and Proton density sequences, Advantage work-station software). Bilateral LGN were identified and manually extracted, the maximum heights and volumes of LGN were compared with clinical damage to the optic disc and visual function.Results:The maximum height(right 4.36±0.62mm, left 4.32±0.62mm) and volume(right 97.48±27.61mm3, left 92.68±25.79mm3)of bilateral LGN in POAG group were significantly less than normal control group(5.02±0.42mm, 4.99±0.41mm and 143.46±22.81 mm3,142.88±20.47 mm3) (p<0.001). In glaucoma group, the maximum height and volume of bilateral LGN were statistically negatively correlated with CDR, positively correlated with RNFLT, and positively correlated with MS, negatively correlated with MD*(p<0.05). In normal group, morphological changes of LGN varied inconsistently with parameters of optic disk, visual function or ages (p>0.05).Conclusions:LGN atrophy in POAG was altered in a manner consistent with damage to the optic disk and visual function. The morphological changes of LGN measured by MRI in this study may be a useful means for quantifying neuropathy of optic nerve loss of visual function in POAG. Part 2 Nerve fibers damage of the central visual pathway in POAGPurpose:To investigate the damage to nerve fiber of visual pathway in patients with primary open angle glaucoma (POAG) by tract-based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI), and correlation with the clinical severity of glaucoma (damage to the optic disc and loss of visual function) and LGN atrophy.Methods:25 individuals with POAG and a comparison group of 24 healthy controls were recruited in the study as above. DTI of the visual pathway was performed with a 3.0-T MR scanner. Diffusivity changes of nerve fiber in the visual pathway were calculated by TBSS analysis of DTI (FMRIB's Diffusion Toolbox), including mean diffusivity (MD) and fractional anisotropy (FA) values. CDR, RNFLT around the optic disc, loss of visual function and LGN atrophy were evaluated for comparison with DTI parameters.Results:Compared with normal controls, bilateral optic tracts and optic radiations of POAG patients showed significantly decreased FA and increased MD (p< 0.05). In glaucoma group, FA values for optic tracts and optic radiations varied consistently with CDR, RNFLT, and visual function analysis (MS and MD*), respectively (p< 0.05). MD values for optic tracts correlated with these ophthalmological measurements (p< 0.05), while no significant correlation was observed between MD values for optic radiations and the ophthalmological measurements (p> 0.05). FA values for optic tracts and optic radiations varied consistently with LGN atrophy (p< 0.05), and the optic tract presented more severe injuries than that of the optic radiation (p< 0.05). In control group, no correlation was found between diffusion indices (FA and MD) and ages(p> 0.05).Conclusions:The optic tract and optic radiation of POAG patients were injured and varied consistently with damage to the optic disc and loss of visual function. TBSS of DTI is an objective and effective means for detecting loss of cortical nerve fibers in POAG. Part 3 Brain function Changes of resting-state MRI in POAGPurpose:To investigate the changes of brain function of resting-state MRI in POAG.Methods:25 individuals with POAG and a comparison group of 24 healthy controls were recruited in the study as above. Resting-state MRI of the whole brain was performed with a 3.0-T MR scanner. Regional homogeneity (ReHo) analysis was used (REST software). Brain regions with significant difference of brain function of resting-state between these two groups were showed.Results:Compared with normal controls, in glaucoma group, ReHo of brain function of resting-state in bilateral occipital lobe, inferior frontal gyrus, right temporal lobe, was decreased(p< 0.05), while bilateral dorsal thalamus, superior frontal gyrus, pontine back, and fusiform gyrus showed increased ReHo(p< 0.05).Conclusions:POAG patients showed an abnormality of brain functional activity of resting state in several brain regions, this kind of multiple brain region dysfunction may participate in the pathogenesis of POAG.