Abstract
The purpose of this study is to investigate brain functional changes in patients with intermittent exotropia (IXT) by analyzing the amplitude of low-frequency fluctuation (ALFF) of brain activity and functional connectivity (FC) using resting-state functional magnetic resonance imaging (rs-fMRI). There were 26 IXT patients and 22 age-, sex-, education-, and handedness-matched healthy controls (HCs) enrolled who underwent rs-fMRI. The ALFF, fractional ALFF (fALFF) values in the slow 4 and slow 5 bands, and FC values were calculated and compared. The correlations between ALFF/fALFF values in discrepant brain regions and clinical features were evaluated. Compared with HCs, ALFF/fALFF values were significantly increased in the right angular gyrus (ANG), supramarginal gyrus (SMG), inferior parietal lobule (IPL), precentral gyrus (PreCG), and the bilateral inferior frontal gyri (IFG), and decreased in the right precuneus gyrus (PCUN), left middle occipital gyrus (MOG), and postcentral gyrus (PoCG) in IXT patients. The Newcastle Control Test score was negatively correlated with ALFF values in the right IFG (r = −0.738, p < 0.001). The duration of IXT was negatively correlated with ALFF values in the right ANG (r = −0.457, p = 0.049). Widespread increases in FC were observed between brain regions, mainly including the right cuneus (CUN), left superior parietal lobule (SPL), right rolandic operculum (ROL), left middle temporal gyrus (MTG), left IFG, left median cingulate gyrus (DCG), left PoCG, right PreCG, and left paracentral gyrus (PCL) in patients with IXT. No decreased FC was observed. Patients with IXT exhibited aberrant intrinsic brain activities and FC in vision- and eye movement-related brain regions, which extend current understanding of the neuropathological mechanisms underlying visual and oculomotor impairments in IXT patients.
Highlights
Comitant strabismus is a group of developmental diseases involving ocular motility impairment (Ouyang et al, 2017; Li et al, 2018)
There was no report about gray matter (GM) atrophy previously in intermittent exotropia (IXT) patients, we investigated the amplitude of low-frequency fluctuation (ALFF)/fractional ALFF (fALFF) comparisons with gray matter volume (GMV) as an additional covariate to exclude the effect of GM atrophy
The general trend of regional brain activity was similar between the two groups and some regions exhibited significantly higher ALFF values than other brain regions during the resting state, including the bilateral middle temporal gyrus (MTG) and inferior parietal lobule (IPL)
Summary
Comitant strabismus is a group of developmental diseases involving ocular motility impairment (Ouyang et al, 2017; Li et al, 2018). Many authors proposed that IXT is caused by defective binocular fusion in the brain (Guyton, 2006; Brodsky and Jung, 2015). Li et al (2016) found abnormal brain activity in binocular fusion-related cortices in IXT patients using task-based functional magnetic resonance imaging (fMRI). Yang et al (2014) and Tan et al (2016) confirmed that the abnormal brain activity was exhibited in infantile esotropia and congenital comitant strabismus using rs-fMRI, which cannot totally represent the brain functional changes of IXT. No study about IXT, a subtype of comitant exotropia, explores the spontaneous neural activity changes of attenuation of spontaneous blood oxygen level dependent (BOLD) fluctuations using rs-fMRI at present
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