Altered Functional Connectivity Of The Thalamus In Primary Angle-closure Glaucoma Patients: A Resting-state FMRI Study

Objective:Glaucoma is one of the leading irreversible causes of blindness worldwide,and previous studies have shown that there is abnormal functional connectivity(FC)in the visual cortex of glaucoma patients.The thalamus is a relay nucleus for visual signals;however,it is not yet clear how the FC of the thalamus is altered in glaucoma.This study use the methods of static functional connectivity(s FC)and dynamic functional connectivity(d FC)to observe the functional connectivity and variability of the thalamus in primary angle closure glaucoma(PACG)patients,and to analyze the possible relationship between abnormal brain areas clinical ophthalmic parameters.Methods:Eighty-three patients with PACG diagnosed and healthy controls between July2014 and October 2022 were retrospectively analyzed.Thirty-four PACG patients and thirty-three healthy controls who meeting the enrollment criteria and matched for age and sex were included.Patients in the PACG group were diagnosed by senior attending physicians from the First Affiliated Hospital of Nanchang University according to the clinical diagnostic criteria proposed in the Chinese Glaucoma Guidelines(2020)in PACG.All PACG patients underwent complete ophthalmological examinations;included retinal nerve fiber layer thickness(RNFLT),intraocular pressure(IOP),average cup-to-disc ratio(A-CDR),and vertical cup-to-disc ratio(V-CDR).All subjects underwent 3.0T resting-state functional brain MRI data acquisition,after the MRI data were preprocessed,the bilateral thalamus was chosen as the seed points to analyze the s FC at the whole brain level.Meanwhile,the variation coefficients of d FC in the two groups were captured by sliding time window method.Finally,the functional connections of different brain regions were extracted for correlation analysis with clinical ophthalmic parameters.Result:(1)The results of s FC showed that compared with the HCs,the functional connections between the bilateral thalamus and right transverse temporal gyrus as well as left anterior cingulate cortex,and between the left thalamus and left insula were decreased.Concurrently,FC between the bilateral thalamus and left superior frontal gyrus in PACG patients was increased.(2)The results of d FC showed that compared with the HCs,PACG patients had reduced d FC variability between left thalamus and right superior temporal gyrus,right thalamus and right brainstem,and had increased d FC variability between right thalamus and right cerebellar anterior lobe.(3)Correlation analysis showed that the value of s FC between the bilateral thalamus and left superior frontal gyrus was positively correlated with RNFLT and negatively correlated with the A-CDR and V-CDR.Besides,the value of s FC between the left thalamus and left insula was negatively correlated with IOP.Conclusions:In this study,we found abnormal FC changes in the bilateral thalamus of PACG patients,and the s FC and d FC analysis provided complementary results,confirming that the thalamus of PACG patients had extensive abnormal FC of resting states with the brain regions related to vision,hearing,emotional regulation and cognitive control,and there was a certain correlation with clinical ophthalmic parameters.It is suggested that abnormal FC of thalamus plays an important role in disease progression in PACG patients.