Metabolic alterations in the visual cortex of glaucoma patients: Insights from MRS
Poster No:
1952
Submission Type:
Abstract Submission
Authors:
Xiaolin Mei1, Lilin Chen1, Lok Hin Chan1, Celia Tsang1, Allen MY Cheong1
Institutions:
1The Hong Kong Polytechnic University, HKSAR
First Author:
Co-Author(s):
Introduction:
Glaucoma is an irreversible ocular disease characterized by progressive degeneration of retinal ganglion cells and associated visual field impairment. The influence of visual field defects on metabolic processes within the visual cortex remains unclear. Previous studies have yielded inconsistent results regarding metabolic parameters that differentiate glaucomatous from healthy individuals (Aksoy et al., 2019; Bang et al., 2023; Guo et al., 2018; Sidek et al., 2016). To improve metabolite quantification, we employed two Magnetic Resonance Spectroscopy (MRS) sequences: MEGA-PRESS for GABA+ and PRESS for glutamate. We focused on total N-acetylaspartate (tNAA) as a marker of neuronal integrity, glutamate (Glu) for excitatory neurotransmission, and GABA+ for inhibitory function, all of which are critical in visual processing and neurodegeneration.
Methods:
A total of 24 glaucoma patients (mean age 63.71 ± 8.34 years; 10 females) and 23 age-matched healthy controls (mean age 62.43 ± 6.67 years; 12 females) were recruited. Participants underwent comprehensive eye examination, including 24-2 Humphrey visual field testing to assess visual function. Brain metabolites were measured using MEGA-PRESS (320 averages) and PRESS (256 averages) sequences on a 3T Siemens system, with a voxel size of 3*3*3 cm³ positioned in the occipital cortex. Independent paired-t test was used to test the group difference.
Results:
Glaucoma patients exhibited a mean deviation (MD) of -17.9 dB ± 5.87 dB in the 24-2 test. They demonstrated significantly lower tNAA concentrations compared to controls (p < 0.01, BH-corrected). Glu levels also differed significantly, with healthy controls showing concentrations of 6.33 ± 0.62 compared to 5.79 ± 0.82 in glaucoma patients (p < 0.05). No significant differences were found in GABA+ levels (healthy: 2.85 ± 0.48; glaucoma: 2.81 ± 0.48; p > 0.05). In the glaucoma group, tNAA and Glu concentration positively correlated with MD (r = 0.44, p < 0.05; r = 0.48, p < 0.05), indicating that less severe glaucoma was associated with higher metabolite concentrations.
Conclusions:
Our findings indicate reduced tNAA and Glu concentrations in the visual cortex of glaucoma patients, suggesting compromised neuronal integrity and impaired excitatory neurotransmission extending beyond primary visual pathways. The correlations between tNAA and Glu levels with clinical indices provide novel insights into the relationship between retinal alterations and cortical metabolic changes, thereby enhancing our understanding of glaucoma's impact on the central nervous system. Further research shall explore the causal relationships and underlying mechanisms of these metabolic changes in glaucoma.
·The voxel position in MRS and the impaired perception in glaucoma (A). The current MEGA-PRESS and PRESS fittings (B). Glaucoma showed reduced tNAA/Glu concentration and correlated with severity (C/D).
Novel Imaging Acquisition Methods:
MR Spectroscopy 1
Physiology, Metabolism and Neurotransmission:
Physiology, Metabolism and Neurotransmission Other 2
Keywords:
Aging
GABA
Glutamate
MR SPECTROSCOPY
Vision
1|2Indicates the priority used for review
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Provide references using APA citation style.
Bang, J. W., Parra, C., Yu, K., Wollstein, G., Schuman, J. S., & Chan, K. C. (2023). GABA decrease is associated with degraded neural specificity in the visual cortex of glaucoma patients. Communications Biology, 6(1), 679.
Guo, L., Wang, R., Tang, Z., Sun, X., Wu, L., Wang, J., Zhong, Y., Xiao, Z., & Zhang, Z. (2018). Metabolic alterations within the primary visual cortex in early open-angle glaucoma patients: a proton magnetic resonance spectroscopy study. Journal of glaucoma, 27(12), 1046-1051.
Sidek, S., Ramli, N., Rahmat, K., Ramli, N. M., Abdulrahman, F., & Kuo, T. L. (2016). In vivo proton magnetic resonance spectroscopy (1H-MRS) evaluation of the metabolite concentration of optic radiation in primary open angle glaucoma. European radiology, 26, 4404-4412.