Meningeal or meningeal brain bulge refers to the outward expansion of meninges or meninges and brain tissue from the congenital defect of the skull, i.e., the cranial fissure, the incidence of which has been reported differently, and the causes of its formation are not yet fully understood, some believe that it may be related to the neural tube closure disorder, but most scholars believe that it occurs shortly after the neural tube closure, brain tissue through the interstitial defect area of the skull and dura that will develop to form the bulge. Clinically, the meningoencephalic bulges are classified into three major categories according to their location: retrooccipital, fontanelle and basal, with the main type being retrooccipital, accounting for about 75%. Those related to rhinology are fontanelle type and basal type. The fontanelle type includes the nasal frontal type, the nasal sieve type and the nasal orbital type; the basal type is divided into the nasal blade type and the nasal blade type. The basal type is more likely to be diagnosed as a nasal polyp, while the basal type is more likely to be diagnosed as a nasal polyp, as two of the four cases were misdiagnosed as nasal polyps in outside hospitals. Cases 1 and 3 were first seen in our department, and because of the young age of the children, a nasal mass was found, and CT examination was performed promptly, and a skull base defect was found and an early diagnosis was made. Therefore, in children with recurrent nasal discharge and polypoid neoplasm in the nasal cavity, especially those with recurrent high fever, nasal masses should not be removed easily, but imaging must be performed to clarify the diagnosis. Coronal sinus CT can generally detect bone defects at the base of the skull. MRI is not as clear as CT in the case of skull defects, but has higher resolution of the bulging contents, and can observe the morphology of the subarachnoid space, brain parenchyma and ventricles, which is significantly better than CT, and shows well in sagittal position, and can well show the density of the nasal mass and the relationship with the meningeal brain tissue. Therefore, imaging examination can clearly diagnose and accurately determine the site and size of skull base bone defect, and is also important for the selection of surgical procedure. Meningoencephalic bulge into the nasal cavity should be differentiated from nasal glioma, nasal polyp and nasal mucous cyst, etc. In addition to the medical history and clinical signs, imaging examination can also assist in the diagnosis. Nasal glioma shows intact skull on imaging with soft tissue density or soft tissue signal and no enhancement on enhancement scan, nasal polyp also shows soft tissue density but significantly enhanced, and mucus cyst shows a typical non-enhancing homogeneous mass with significant high signal on MRI T2WI.