Abstract: Heterotopic gray matter (HGM) is a rare congenital developmental abnormality caused by the accumulation of neurons in abnormal parts due to the blockage of neuronal migration in the embryonic stage. The authors analyzed the imaging characteristics of a patient with HGM by¹⁸F-fluorodeoxyglucose (FDG) PET/CT-MRI three-mode imaging, in order to improve the understandingof the imaging manifestations of the disease, so as to facilitate accurate diagnosis and timely treatment.