Cranial fibrous dysplasia (FD) is also known as cranial fibrous dysplasia, fibrous degeneration of bone, and fibrous osteoma. The etiology of FD is unknown, and it is thought to be caused by abnormal growth of the mesenchyme that forms bone in the embryonic stage, or metabolic and endocrine disorders. FD is a benign lesion, with fewer malignant lesions, and when malignant, a large number of chondrocytes appear, transforming into chondrosarcoma. Pathology: Bone is destroyed by osteoclasts, and the destroyed part is filled by fibrous connective tissue, i.e., composed of immature bone trabeculae and fibrous mesenchyme. The trabeculae are of different sizes. Fibrous interstitium is mainly composed of spindle-shaped cells arranged in a capsule, with collagen formation. Clinical manifestations] The patients are mostly young people and children, and there are more females than males. In addition to the skull, the bones of the limbs can also be involved. Cranial bone mostly occurs in the fronto-orbital, temporal and parietal bones, and the cranium can be significantly thickened. It usually protrudes outward and rarely grows into the skull; therefore, there are usually no symptoms of brain tissue compression. Involvement of the anterior cranial fossa and orbital plate is more common, and the eyeballs protrude due to orbital narrowing. The lesion is usually located on one side only. If the lesion is located in the saddle region, precocious puberty may occur. Imaging] X-ray examination can have three manifestations: 1, in the skull cap and early for the cystic type, the bone plate of the skull is thinned, the plate barrier is widened, and it is round or oval. 2, in the base of the skull and late for the sclerotic type, the lesion is more extensive, and deformity often occurs, and the bone density is sclerotic changes, which is seen in the base of the anterior cranial fossa and the pteronotum; 3, the mixed type is the one that resides in the cystic and the sclerotic types, and the two types exist at the same time, and are seen in the cranial vault. 4, in the base of the cranial fossa, the cystic and sclerotic type is the one that exists at the same time. The mixed type is the one in which both cystic type and sclerotic type exist together. MRI examination mostly suggests T1 low signal T2 high signal, and the signal is not uniform. Treatment: For those who invade the orbit and optic nerve foramen, causing eyeball protrusion and visual impairment, kyphoscoliectomy and optic nerve foramen decompression are feasible. For the severe bread deformity, local bone resection or chiseling can be used to flatten the protruding area, and the protruding part can also be smoothed with a magic drill. For the cranial cap, craniectomy + cranial repair can be required. Radiotherapy as well as medications have no significant effect. The disease develops rapidly before puberty and usually stops on its own in adulthood, with a good prognosis. Fig. The lesion is located in the left temporal bone, which is the most common site of FD, and is more likely to develop on one side.E suggests that it tends to protrude outward, and seldom grows intracranially, i.e., the inner walls of the skull on both sides are equal to the midline.A, B, C, and D show that the cranium is thickened, with a thinning of the bony plates, and a widening of the baffle, which is rounded or oval in shape.