The Volume Alterations of the Amygdala in Autism Spectrum Disorder: A Meta-Analysis on MRI Study
Authors: Chen Yunhua , Zheng Xiaoli , wang xue , Wen Min , Zhou Bo 
Published: August 2021

Abstract
Background:Due to the unclear etiology and pathogenesis of autism spectrum disorder (ASD), there is still a lack of effective drugs for prevention and treatment of ASD, which can improve the prognosis of autism through early intervention. However, the current diagnostic methods are mainly based on qualitative indicators such as behavioral standards, which cannot timely and accurately diagnose autism. A large number of studies have found abnormal amygdala volume in autism patients.This study aimed to evaluate amygdala volume in patients with ASD and elucidat the potential relationship between amygdala volume and ASD by using systematic review and meta-analysis, with a view to providing a new approach for early diagnosis of ASD. Methods: Comprehensive electronic search in Pubmed, Web of Science, EBSCOhost, Embase, the Cochrane Review Library, CNKI and WanFang data to find original articles about the relationship between amygdala volume and the ASD. Heterogeneity across studies were assessed using I2 and Q statistics. Random-effects model was used to estimate the odds ratios (ORs) with 95% confidence intervals (CIs). Sensitivity analyses to assess the influence of individual studies on the pooled estimate. Publication bias was investigated using funnel plots and Egger's regression test. If the funnel plot is asymmetry, the reason is distinguished by using the contour-enhanced funnel plots and trim-and-fill method. Results: The results showed that the volume of the right amygdala significantly increased in patients with ASD (WMD: 0.137, 95% CI: [0.051, 0.222], Z = 3.132, P < 0.001). Subgroup analysis by age showed that the volume of the left amygdala significantly increased in young child patients with ASD (MD: 0.153, 95% CI: [0.025, 0.281], Z = 2.341, P < 0.05), but not change in child (MD: 0.153, 95% CI: [-0.026, 0.332], Z = 1.672, P > 0.05), adolescent (MD: 0.095, 95% CI: [-0.189, 0.379], Z = 0.654, P > 0.05) and adult (MD: 0.068, 95% CI: [-0.103, 0.240], Z = 0.781, P > 0.05) ASD patient. The volume of the right amygdala significantly increased in young child (MD: 0.174, 95% CI: [0.043, 0.304], Z = 2.60, P < 0.05) and child patients(MD: 0.192, 95% CI: [0.040, 0.343], Z = 2.480, P < 0.05) with ASD, but not change in adolescent (MD: 0.208, 95% CI: [-0.201, 0.618], Z = 0.998, P > 0.05) and adulthood patients (MD: 0.126, 95% CI: [-0.040, 0.291], Z = 1.488, P > 0.05). Subgroup analysis by gender showed that the volume of the left amygdala not change in male (MD: 0.101, 95% CI: [-0.031, 0.233], Z = 1.498, P > 0.05) and female group (MD: 0.067, 95% CI: [-0.023, 0.157], Z = 1.452, P > 0.05). The volume of the right amygdala significantly increased in female group (MD: 0.099, 95% CI: [0.019, 0.178], Z = 2.439, P < 0.05), but not change in male group (MD: 0.117, 95% CI: [-0.014, 0.248], Z = 1.755, P > 0.05).Conclusions: The volume of the amygdala significantly increased in young children with ASD. These findings suggest that the volume of the amygdala in young children might be a potential early auxiliary imaging diagnosis method of ASD.