Table 2.
Outcomes of studies with structural brain analysis.
| Author, year | Brain area analyzed | Parameter analyzed | Results |
|---|---|---|---|
| DTI | |||
| Bolacchi et al., 2012 | Intraorbital optic nerve at two different levels: proximal and distal to the ONH | Fractional anisotropy (FA) and mean diffusivity (MD) | At early stage higher MD at the proximal site with respect to the distal site. In contrast, at severe stages both the proximal and the distal portion showed altered MD. FA is altered in both stages both in the proximal and distal part. |
| Boucard et al., 2016 | White matter of all brain | FA and MD | Reduced FA in clusters in bilateral occipital pole (comprising OR and forceps major), superior parietal lobe, body and splenium of corpus callosum. |
| Chen Z. et al., 2013 | White matter of all brain | FA and MD. Correlation with clinical measurement | Bilateral OT and OR showed decreased FA and increased MD. FA correlates with CDR, RNFL thickness and visual function. |
| El-Rafei et al., 2011 | Optic radiation | Axial, radial, mean diffusivities and FA | Glaucoma subjects have increased radial diffusivity and mean diffusivity significant voxels with a main concentration in the proximal part of the right optic radiation |
| El-Rafei et al., 2013 | A specified ROI on the segmented optic radiation | Different diffusion tensor derived measures. Their ability for detecting and discriminating different glaucoma entities | The discrimination accuracy between healthy and glaucoma (POAG and NTG) subjects was 94.1%, between healthy and POAG was 92.4% and it increased to 100% between healthy and NTG groups. Discrimination between glaucoma entities (POAG and NTG) had an accuracy of 98.3%. |
| Engelhorn et al., 2011 | Optic radiation | Volume of the optic radiation and grading of microangiopathic lesions (mild, moderate and severe) | 44% glaucoma patients showed significant rarefaction of the optic radiation: the volume was reduced to 67 ± 16% compared with controls. Cerebral microangiopathy of OR was higher among glaucoma patients. |
| Frezzotti et al., 2014 | Whole brain white matter | FA, axial diffusivity (AD), radial diffusivity (RD) | Altered integrity (decreased FA or increased diffusivities) along the visual pathway (optic tracts, chiasm, radiation) of POAG and also in nonvisual WM tracts (superior longitudinal fascicle, anterior thalamic radiation, corticospinal tract, middle cerebellar peduncle). |
| Frezzotti et al., 2016 | Whole brain white matter | FA, AD, RD. Differences between healthy and whole POAG and between healthy and early stage POAG. | Decreased FA and higher AD along the visual pathway (optic tracts, chiasm, radiation) of POAG and also in nonvisual WM tracts (superior longitudinal fascicle, supramarginal gyrus and superior parietal lobule). Similar results in the early stage glaucoma. |
| Garaci et al., 2009 | Optic nerve and optic radiation | FA and MD. Correlation with disease severity | POAG NO and OR had significantly higher MD and significantly lower FA. A negative correlation between mean FA for the optic nerves and glaucoma stage was observed. |
| Giorgio et al., 2018 | Whole brain white matter | FA, AD, RD. Differences between healthy, POAG and NTG. | Decreased FA and higher AD along the visual pathway (optic tracts, chiasm, radiation) and also in nonvisual WM tracts (superior longitudinal fascicle, WM adjacent to precuneus, inferior frontal gyrus, superior parietal lobe) in both POAG and NTG. Differences were found in the nonvisual areas abnormalities between POAG and NTG. |
| Kaushik et al., 2014 | Optic radiation | RD, AD, MD, FA in OR. OR fibers were separated into tracts subserving the superior of inferior hemifield of the visual field. | FA was lower and MD was higher in POAG OR compared with controls. Unaffected OR tracts showed changes in RD compared with controls |
| Lu et al., 2013 | Occipital white matter | FA | Occipital white matter in POAG had lower FA values. |
| Michelson et al., 2013 | Optic radiation | FA, AD and RD of the optic radiations and their correlation with glaucoma severity indicators | DTI-derived parameters of the axonal integrity (FA, AD) and demyelination (RD) of the optic radiation are linked to HRT-based indices of glaucoma severity. |
| Murai et al., 2015 | Optic radiation | FA of optic radiation. Correlation with glucose metabolism in the striate cortex studied with PET | FA in optic radiations was lower in patients with glaucoma. There were significant correlations between FA of the optic radiation and ipsilateral striatal glucose metabolism. |
| Nucci et al., 2012 | Optic nerve | FA and MD. Correlation with optic nerve structure (GDx-VCC, HRT, OCT) | DTI parameters of the axonal architecture of the optic nerve show good correlation with morphological features of the optic nerve head and RNFL documented with GDx-VCC, HRT-III and OCT. |
| Omodaka et al., 2014 | Optic nerve | FA and AD. Correlation with optic nerve structure (OCT) and MD | DTI parameters correlated with RNFL and MD at VF. |
| Schoemann et al., 2014 | Optic radiation | FA. Correlation with the extent of cerebral white matter lesions (WML). | There was a significant correlation between FA and WML in POAG regarding the total brain, the periventricular region, and the optic radiation in both hemispheres. |
| Sidek et al., 2014 | Optic nerve and optic radiation | FA and MD and their discriminant power between mild and severe glaucoma and correlation with RNFL. | FA and MD in the optic nerve and optic radiation decreased and increased respectively as the disease progressed. FA at the optic nerve had the highest sensitivity (87%) and specificity (80%). FA values displayed the strongest correlation with RNFL thickness in the optic nerve. |
| Tellouck et al., 2016 | Optic radiations | FA, MD, RD, AD | FA was lower and RD higher than controls. Correlation with functional and structural damage. |
| Wang et al., 2013 | Optic nerve | FA, MD. Correlation with RNFL measured with OCT | FA was lower and MD higher than controls. Correlation with RNFL. |
| Zhang et al., 2012 | Optic nerve | FA, MD. Correlation with RNFL measured with OCT | FA was lower and MD higher than controls. Correlation with RNFL. |
| Zhou et al., 2017a | Optic tract and optic radiation | FA, RD, AD, MD. Correlation with visual field loss and RNFL | FA was lower along the optic tracts and radiations in POAG. FA correlated with visual field loss but not with RNFL. |
| Zikou et al., 2012 | Whole brain white matter | FA and MD | A significant decrease of FA was observed in the inferior fronto-occipital fasciculus, the longitudinal and inferior frontal fasciculi, the putamen, the caudate nucleus, the anterior and posterior thalamic radiations, and the anterior and posterior limbs of the internal capsule of the left hemisphere. |
| VBM | |||
| Boucard et al., 2009 | whole brain 21 mm diameter VOI at the posterior pole: 1 posterior and 1 anterior in both superior and inferior banks of the calcarine sulcus in each hemisphere | Changes in gray matter density in the all brain and VOI analysis. | (1) bilateral reduction of gray matter density on the medial aspect of the occipital lobe, at the anterior half of the calcarine fissures. (2) gray matter density is more reduced in the anterior than in the posterior region. |
| Chen Z. et al., 2013 | Whole brain | Differences in gray matter volume (GMV) | POAG showed a significantly decreased GMV in the lingual gyrus, calcarine gyrus, postcentral gyrus, superior frontal gyrus, inferior frontal gyrus, and rolandic operculum of both sides, and in the R inferior occipital gyrus, L paracentral lobule, R supramarginal gyrus, and R cuneus. The GMV was significantly larger in POAG in both sides of the middle temporal gyrus, inferior parietal gyrus, angular gyrus, and L superior parietal gyrus, L precuneus, and L middle occipital gyrus. |
| Frezzotti et al., 2014 | Whole brain | Differences in gray matter volume | POAG patients showed brain atrophy in both visual cortex and other distant GM regions (frontoparietal cortex, hippocampi and cerebellar cortex). |
| Frezzotti et al., 2016 | Whole brain | Differences in gray matter volume | No differences considering whole POAG. Lower GM volume in occipital cortex and hippocampus only in advanced POAG. |
| Giorgio et al., 2018 | Whole brain | Differences in gray matter volume between healthy, POAG and NTG. | Both groups showed reduced GMV in visual cortex and beyond it. Compared with NTG, POAG had more atrophic visual cortex. |
| Hernowo et al., 2011 | ROI: optic nerve, optic chiasm, optic tracts, lateral geniculate nuclei (LGN) and the optic radiations | Volume of ROIs and correlation with VF sensitivity | Compared with the controls, subjects with glaucoma showed reduced volume of all structures along the visual pathway, including the optic nerves, the optic chiasm, the optic tracts, the LGN, and the optic radiations. No significant correlation between the volume of visual pathway and MD of VF. |
| Jiang et al., 2017 | Whole brain | Differences in gray matter volume. Correlation with RNFL | The regions of the brain with increased volumes compared with the control group were the midbrain, L brainstem, frontal gyrus, cerebellar vermis, L inferior parietal lobule, frontal lobe, caudate nucleus, thalamus, precuneus, and BA 7, 18, and 46. |
| Li et al., 2012 | Whole brain | Differences in gray matter volume | Compared with controls, brain regions with GM density changes were not found in the early stage but only in the advanced-late stage of POAG patients. GM density reduction was mainly located in the bilateral primary visual cortex (BA17 and BA18), bilateral paracentral lobule (BA5), R precentral gyrus (BA6), R middle frontal gyrus (BA9), R inferior temporal gyrus (BA20), R angular gyrus (BA39), L praecuneus (BA7), L middle temporal gyrus (BA21), and superior temporal gyrus (BA22). Increased GM density was found in BA39. In the advanced-late stage of POAG, some reduced GM density areas were related to binocular mean defect (MD) and disease duration. |
| Wang et al., 2016 | Whole brain and ROI (LGN, V1, V2, amygdala, hippocampus) | Gray matter volume. Correlation with clinical parameters. | Significant volume shrinkages in the LGN bilaterally, R V1, L amygdala and no difference in V2 and hippocampus. Correlation with clinical variables. |
| Williams et al., 2013 | 93 brain structures | Differences in gray matter volume | 5 differed regions differ significantly between POAG and healthy: all were larger in the glaucoma group and were all components of the visual association cortex. Total brain volume was also larger in the glaucoma group. |
| Zhang et al., 2015 | Whole brain | Differences in gray matter volume | Compared to controls, a region with significant reduction of GMV was detected in the anterior calcarine fissure of advanced POAG patients but not in early-moderate POAG. |
| Zikou et al., 2012 | Whole brain | Differences in gray matter volume | In POAG there were a significant reduction in the L visual cortex volume, the L lateral geniculate nucleus, and the intracranial part of the ONs and the chiasma. |
| SBM | |||
| Bolacchi et al., 2012 | Whole brain cortex | Cortical thickness on flat map | Local thinning in the visual cortex areas in POAG: 1 cluster in BA19 LH (lingula), 2 cluster in BA19 RH (fusiform gyrus and cuneus). |
| Wang et al., 2016 | V1 and V2 | Cortical thickness. Correlation with clinical parameters. | The right V1 thickness was significantly reduced in glaucoma. Correlation with clinical variables. |
| Yu et al., 2013 | Whole brain cortex | Cortical thickness. Correlation with clinical parameters. | POAG patients showed bilateral cortical thinning in the anterior half of the visual cortex around the calcarine sulci (calcarine cortex) including the right BA 17 and left BA 17 and BA 18. Some smaller regions located in the left middle temporal gyrus (BA37) and the fusiform gyrus (BA19) also showed thinning relative to normal controls. The thickness of the VC correlated positively with RNFL thickness. Significant differences between mild and severe groups were observed. |
| Yu et al., 2014 | ROIs: V5/MT+, anterior and posterior subregions of V1 and V2 | Cortical thickness and volume in normal, mild (MP) and severe (SP) POAG patients. Correlation with clinical parameters | Decreased cortical thickness in V5/MT+ area in the MP group and in all of the visual areas except the posterior subregion of V1 in the SP group. Gray matter volume in the posterior subregion of V2 and mean curvature in the V5/MT+ were significantly changed in the SP group. The clinical measurements were positively correlated with the cortical thickness. |
| Yu et al., 2015 | ROIs: V1, V2, ventral V3, V4 and V5/MT+ | Cortical thickness in normal, mild (MP) and severe (SP) POAG patients. Correlation with clinical parameters | Decreased cortical thickness was detected in the bilateral V5/MT+ areas in the MP group and the L V1, bilateral V2 and V5/MT+ areas in the SP group. Cortical thinning of the bilateral V2 areas was detected in the SP group compared with the MP group. Cortical thinning of these visual areas was related to the ophthalmologic measurements. |
BA, Brodmann Area; LH, Left Hemisphere; RH, Right Hemisphere; VOI, Volume of interest; OR, optical radiation; OT, optic tracts; CDR, cup-disc ratio; RNFL, retinal nerve fiber layer; WM, white matter; GM, gray matter; GMV, gray matter volume; MD, mean deviation; MT+, middle temporal visual area.