Regional Homogeneity And Frequency-dependent Alterations In The Amplitude Of Low-frequency Fluctuations In Primary Angle-closure Glaucoma:A Resting-state FMRI Study

Objective: To investigate the altered regional homogeneity(Re Ho) and amplitude of low-frequency fluctuation(ALFF) of the brain using resting-state functional magnetic resonance imaging(rs-f MRI) within different band of fluctuation( slow-4: 0.027-0.073Hz; slow-5: 0.01-0.027Hz) in patients with primary angle-closure glaucoma(PACG).Methods: Forty PACG patients and 40 age- and gender- matched healthy controls(HC) were included in the rs-f MRI scans, the data preprocessing was performed using Data Processing Assistant For Resting-state(DPARSF). Data analysis include:(1) The brain Re Ho of two groups were calculated and compared with two-sample t test. Then the correlations between Re Ho and the clinical measures were analyzed.(2) The brain ALFF of two groups were calculated, a two-way repeated-measures analysis of variance(ANOVA)were performed using SPM8 to analyze the effects of group(PACG HC) and frequency band(slow-4, slow-5). Then, two-sample t tests were performed to observe the ALFF between PACG and HC in slow-4 and slow-5.Results :(1) Compared to HC, PACG patients showed decreased Re Ho in the right fusiform gyrus, left middle occipital gyrus, left inferior occipital gyrus, left middle temporal gyrus, left superior parietal lobule, bilateral precentral gyrus, left postcentral gyrus, left paracentral lobule, meanwhile, Re Ho values significantly increased in bilateral cerebellum posterior lobe, right superior frontal gyrus( p<0.05,GRF corrected). Decreased Re Ho in the right fusiform gyrus(r= 0.452, p=0.003), left middle occipital gyrus(r= 0.472, p=0.002) was positively correlated with retinal nerve fiber thickness(RNFLT), increased Re Ho in superior frontal gyrus(r= 0.443, p=0.004) was negatively correlated with visual acuity(VA).(2) Regional differences in ALFF at two bands showed that right caudate nucleus, the left inferior orbitofrontal gyrus had increased ALFF in slow-5 band compared to slow-4(p < 0.05, FDR corrected). Compared to HC, precuneus, cuneus, bilateral lingual gyrus, bilateral middle occipital gyrus, bilateral calcarine, bilateral postcentral gyrus, right precentral, right middle temporal gyrus, right middle frontal gyrus, bilateral superior parietal lobule, right paracentral lobule, left inferior parietal lobule showed decreased ALFF, meanwhile, left superior and inferior temporal gyrus, left cerebellum posterior lobe, bilateral parahippocampa gyrus, left inferior frontal gyrus, right limbic lobe, right insula, posterior cingulated showed increased ALFF(p < 0.05, FDR corrected).Conclusions:(1) PACG patients was associated with altered Re Ho in visual cortices, motor and sensory cortices, cognitive and emotional processing regions. Moreover, the alterations of Re Ho in multiple brain regions were correlated with the severity of PACG.(2) PACG patients had abnormal ALFF within and beyond the visual pathway. Slow-5 band and slow-4 band could detect brain abnormalities from a different perspective, it provides new insights into the understanding of the pathological changes of PACG.