Objective:To analyze whether patients with myasthenia gravis (MG) have cognitive impairment and changes of brain structure, and explore the possible mechanisms of cognitive impairment in MG patients from the perspective of brain structure.Methods:Twenty-eight patients with MG admitted to Department of Neurology, First Affiliated Hospital of Soochow University from July 2019 to December 2021 were selected as MG group, and 30 family members from MG patients or healthy subjects who underwent physical examination in Physical Examination Center during the same period were selected as healthy control group. Neuropsychological test was used to evaluate the cognitive function. VBM was used to analyze the changes of brain structure on structural MRI (sMRI). Correlations of gray matter volumes of different brain regions with cognitive function between the two groups were analyzed.Results:Compared with the healthy control group, the MG group had significantly decreased scores of Mini-mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Clock Painting Test (CDT), and Verbal Fluency Test (VFT), and significantly decreased Rey Auditory Verbal Learning Test (RAVLT) immediate memory and delayed memory scores, while statistically increased time consuming in Making Track Test Part A (TMT-A), and Hamilton Depression Scale (HAMD) and Hamilton Anxiety Scale (HAMA) scores ( P<0.05). Compared with healthy control group, MG group had significantly decreased gray matter volumes of the left orbital superior frontal gyrus, right orbital middle frontal gyrus, right triangular inferior frontal gyrus, left insula, left middle frontal gyrus, right superior limbic gyrus, right anterior cingulate gyrus, right lateral cingulate gyrus, left medial cingulate gyrus, left lateral cingulate gyrus, left medial superior frontal gyrus, and left dorsalateral superior frontal gyrus ( P<0.05). Correlation analysis showed that gray matter volume in the left insula was negatively correlated with time consuming in Stroop Color-Word Test-A ( r=-0.407, P=0.035). Conclusion:Patients with MG may have cognitive decline and gray matter cortical atrophy of some brain regions, and brain areas with gray matter cortical atrophy correspond to areas of cognitive impairment.