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Normal tension glaucoma (NTG) is a neurodegenerative disease involves multiple brain areas, but the mechanism remains unclear. The aim of this study is to investigate the correlation between structural injury and functional reorganization in the brain of NTG, using resting-state functional MRI and diffusion kurtosis imaging (DKI) data acquired for 26 NTG patients and 24 control subjects. Granger causality analysis (GCA) was used to calculate the effective connectivity (EC) between visual cortices and the whole brain to reflect the information flow. The fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) derived from DKI of visual cortices were extracted to evaluate structural injury. Microstructural abnormalities were detected in bilateral BA17, BA18, and BA19. NTG patients showed significantly decreased EC from BA17 to higher visual cortices and increase EC from higher visual cortices to BA17. The EC from BA17 to posterior cingulate cortex (PCC) and from PCC to BA17 both significantly increased, while the EC from right BA18 and BA19 to PCC significantly decreased. Decreased EC between somatosensory cortex and BA17, as well as the decreased ECs between supramarginal gyrus (SMA) and BA17/BA19 were detected. Several abnormal ECs were significantly correlated with microstructural injuries of BA17 and BA18. In conclusion, NTG causes reorganization of information flows among visual cortices and other brain areas, which is consistent with brain microstructural injury., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Purpose: To investigate if abnormal interhemispheric homotopic functional connectivity were accompanied by corresponding anatomic connectivity changes in primary open-angle glaucoma (POAG) patients, and to relate connectivity changes with retinal nerve fiber layer (RNFL) thickness and ganglion cell complex (GCC) thickness., Methods: Resting-state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) were performed in 16 POAG patients and 19 healthy controls. Indices of interhemispheric homotopic functional connectivity and the underlying anatomic connectivity changes were derived with voxel-base whole-brain voxel-mirrored homotopic connectivity (VMHC) analyses and VMHC-guided probabilistic tractography. Pearson correlation analyses were used to explore the correlations between interhemispheric homotopic functional connectivity changes and anatomic connectivity alterations, and RNFL and GCC thickness., Results: Reduced VMHC values between bilateral homotopic cortical areas located in Brodmann area (BA)17, BA18, and BA19. Decreased anatomic connectivity connecting bilateral visual cortical areas inside BA17 and BA18 were observed in POAG patients. Furthermore, positive correlations between average RNFL thickness and reduced VMHC values of BA17 (r = 0.572, P = 0.021)/BA18 (r = 0.600, P = 0.014)/BA19 (r = 0.550, P = 0.027) are found using Pearson correlation analyses., Conclusions: Combinations of interhemispheric homotopic functional connectivity and anatomic connectivity changes may help to elucidate the mechanism of interhemispheric synchronization injury in POAG patients. Reduced VMHC values positively correlate with glaucomatous changes of RNFL thickness, which strengthens the hypothesis that POAG affects the visual cortex using a novel functional MRI characteristic.

Objective: To study the alteration of the optic radiations in patients with primary open-angle glaucoma (POAG) by diffusion tensor imaging (DTI) and tractography, and to reveal the correlation between the DTI derived parameters and the severity of the disease. Methods: A total of 24 patients with POAG and 20 age- and gender-matched healthy controls were enrolled in this study from January 2011 to June 2013.All subjects underwent ophthalmoscopy, standard automatic perimetry, intraocular pressure measurement and MRI scanning.All the eyes of POAG patients were evaluated by Hodapp-Anderson-Parrish (HAP) system.Then the stages of bilateral eyes were added together to evaluate the disease severity.Tractography was used to measure the fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD) of the optic radiations of these subjects.The results of the two groups were compared.Partial correlation was then used to reveal the correlation between these derived DTI parameters and the severity of POAG. Results: Compared with health controls, POAG patients showed significant decreased FA ( t =-3.299, P =0.002) and AD ( t =-2.485, P =0.013), increased RD ( t =2.365, P =0.018) in optic radiation .The alteration of MD was not significant ( t =0.719, P =0.454). Mean FA values of the optic radiations were negatively correlated with POAG stages ( r =-0.643, P = 0.001), while mean RD values ( r =0.570, P = 0.004) and mean MD values ( r = 0.448, P = 0.028) were positively correlated with POAG stages.No correlation between AD values and severity of POAG was found. Conclusion: In the optic radiations of POAG patients, the FA values and AD values decrease, while RD values increase, indicating the fiber integrity changes.The alterations of FA, RD and MD are correlated with disease severity.

Background: Indirect traumatic optic neuropathy (ITON) is a devastating cause of permanent visual loss. Axonal degeneration, the characteristic pathological change of ITON, cannot be assessed by conventional imaging. Diffusion tensor imaging (DTI) has been widely used as a sensitive non-invasive imaging technique to obtain information on axonal integrity., Purpose: To study time-dependent changes in ITON patients with DTI and to provide imaging evidence for clinical diagnosis and therapy., Material and Methods: We enrolled 28 subjects with unilateral ITON who underwent detailed ocular examinations and magnetic resonance imaging (MRI) examinations. The differences between injured optic nerve (ON) and contralateral ON were tested. The patients were divided into three groups based on time (from injury to examination). Groups 1, 2, and 3 corresponded to the time taken from injury to examination: <7 days, 7-30 days, and >30 days, respectively. DT magnetic resonance imaging (MRI) differences among the groups were compared, including the relationship between diffusion parameters and mean thicknesses of the peripapillary retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) in the macular area., Results: Compared with contralateral ON, we observed reduced fractional anisotropy (FA) of injured nerves in group 2. Reduced FA and decreased axial diffusivity (λ//) and increased radial diffusivity (λ┴) and mean diffusivity (MD) of injured nerves were observed in group 3. The mean FA value of injured nerves showed a progressive decreasing trend, and mean λ┴ value exhibited a progressive increasing trend. For injured eyes, the MD and λ┴ increases strongly correlated with the decreased mean thicknesses of RNFL and GCC. Conversely, FA was significantly associated with mean RNFL thickness., Conclusion: DT-MRI parameters could be useful biomarkers in detecting ON changes in ITON patients., (© The Foundation Acta Radiologica 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.)

Objective: Optic neuritis (ON) is defined as an inflammation of the optic nerve and provides a useful model for studying the effects of inflammatory demyelination of white matter. The aim of this study was to assess the diffusion changes in both the optic nerve and optic radiation in patients with acute and chronic ON using diffusion tensor (DT) MRI. Methods: 33 patients with idiopathic demyelinating optic neuritis (IDON) and 33 gender- and age-matched healthy controls were examined with DT-MRI and with T1 and T2 weighted MRI. Results: Compared with controls, both first-episode and recurrent patients with IDON in the acute stage showed significantly increased radial diffusivity (λ˔) and decreased mean fractional anisotropy (FA) in the affected nerves. Reduced FA, increased λ˔, mean diffusivity (MD) and axial diffusivity (λ‖) were determined in patients with subacute IDON. We found no significant difference in the directional diffusivity of optic radiation in patients whose disease had lasted less than 1 year compared with healthy controls. However, significant changes in the FA and lH of the optic radiation were detected in patients with disease duration of more than 1 year. Conclusion: These results show the great potential and capacity of DT-MRI measures as useful biomarkers and indicators for the evaluation ofmyelin injury in the visual pathway. [ABSTRACT FROM AUTHOR]