Reduced Functional and Anatomic Interhemispheric Homotopic Connectivity in Primary Open-Angle Glaucoma: A Combined Resting State-fMRI and DTI Study

Abstract

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.