| Objective:Comitant strabismus(CS)is a common form of strabismus,which affects 1~4.2% of the population,it is characterized by a constant angle of deviation in different directions of gaze.Asian exotropia is more common,while Caucasian esotropia is more common.Over the past 10 years,the ratio of exotropia to esotropia in China has gradually increased,mainly due to the increase numbers of patients with concomitant exotropia and the relative decrease numbers of patients with esotropia(mainly accommodative esotropia).In clinical practice,comitant exotropia strabismus also presents with stereopsis impairment,especially in those patients with onset in early childhood,whose stereopsis is substantially impaired,it also may lead to compromised binocular vision and amblyopia.Although previous neuroimaging studies have found a relationship between strabismus and the cerebral cortex,the pathological mechanism of different types of strabismus are still not fully understood.The research in this paper analyzed that whether the brain structure of patients with common exotropia was damaged by voxel-based morphometry(VBM)and structural network from the aspects of connectivity based on diffusion tensor imaging(DTI)datas,which was expected to provide new clues for the research about the pathological mechanism of patients with comitant exotropia strabismus.Subjects and Methods:In this study,a total of 20 patients with comitant exotropia strabismus and 15 healthy subjects with matched age,sex status and education were recruited in General Hospital of Tianjin Medical University from July 2017 to January 2019.All participants underwent Siemens Prisma 3.0 T functional magnetic resonance imaging scans with acquisition of diffusion tensor images and 3D high-resolution T1 WI structural images.3D T1 WI structural images were adopted a network-based statistic(NBS)approach to assess between-group differences in inter-regional white matter connections.DTI datas were processed by VBM to analyze the abnormal gray matter volume of the patients with common exotropia.Results:1.Eliminating the serious motion artifacts,15 patients(7 males and 8 females)in the CES group,aged 19-33 years,averaged 26±4 years,and 15 patients(7 males and 8 females)in the NC group,aged 19-32 years,averaged 26.3±3.5 years were finally enrolled.Compare with NC group in general condition,there was no statistical difference between CES and NC group(P > 0.05).2.Compared with NC group,CS groups showed smaller grey matter volumes at the right middle temporal gyrus(TPOmid.R),the left supramarginal gyrus(SMG.L)and the left inferior cerebellum(Cerebelum9.L),while greater grey matter volume was found at the right precentral gyrus(PreCG.R)and the right gyrus rectus(REC.R).3.Using the NBS analysis,the significantly reduction of altered white matter connections in the CES compared with the controls were find.This network was composed of 12 nodes,including the left parahippocampal gyrus(PHG.L),the bilateral amygdala,the bilateral(AMYG),the bilateral fusiform gyrus(FFG),the bilateral lingual gyrus(LING),the bilateral hippocampus(HIP),the right inferior occipital gyrus(IOG.R),the right cuneus(CUN.R),the left gyrus rectus(REC.L),the left precuneus(PCUN.L),the left calcarine fissure and surrounding cortex(CAL.L),the left temporal pole: middle temporal gyrus(TPOmid.L),the right inferior temporal gyrus(ITG.R).Conclusions:1.It was found that the patients with CES cause the atrophy of GMV in many brain regionswhich suggesting that the patients with CES may have ocular dyskinesia and fusion dysfunction.In addition,the increase of GMV at the right precentral gyrus and the right gyrus rectus may reflect that patients with CES compensate for atrophy of the visual system by increasing the volume of the oculomotor nerve area.2.Varying degrees of the brain white matter structural network connections were damaged in patients,which indicated that mapping brain WM structural network may be helpful for better understanding the neuromechanism of CES. |
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