AIM:To study the imaging features of extraocular muscles (EOMs) and ocular motor nerves of a Chinese family with congenital fibrosis of extraocular muscles (CFEOM) by magnetic resonance imaging (MRI), and approach the etiopathogenisis of CFEOM to provide theory basis for the treatment of it.METHODS:In a autosomal dominant inheritance of CFEOM family, 2 cases of three generations were scanned by high resolution MRI, and 12 healthy people were selected as control group. Scanning method:orbital region were performed 3mm, T1-weighted imaging(T1WI); intracranial region were performed 1mm, 3D FIESTA imaging. The changes of EOMs and ocular motor nerves of two groups were compared.RESULTS:Compared to healthy people, the volumes of patients'' 5 EOMs were smaller than those of control group, especially the superior rectus (P＜0.05) . And diameters of ocular motor nerves(oculomotor nerve, abducent nerve) were smaller, too (P＜0.05) .CONCLUSION:The EOMs of patients with CFEOM are atrophied compared with that of healthy people, intracranial ocular motor nerves are dysplasia, which indicates that this disease can be caused by dysplasia of ocular motor nerves.