[A case of giant osteoma in the occipital bone]

A 51-year-old female patient, admitted with a chief complaint of dizziness, had bulging of the occipital area, which had started insidiously. On admission, a bony hard swelling with a smooth surface was noted in the left occipital region, extending over the midline of the skull. Plain X ray films revealed a uniform shadow of an osteoid mass inside the occipital bone. A tomogram indicated that the mass originated in the diploë or outer table of the skull, although there was no evidence of destruction of the inner table. CT scan revealed mixed density mass with high density of bone and an irregularly shaped low density area. In the T1-weighted images of MRI, the entire mass showed a low intensity, while in the T2-weighted image the mass showed 3 areas with different intensities. Bone scintigraphy was performed with 99mTc-MDP and revealed an image of accumulation in the mass. Carotid and vertebral angiograms were negative for evidence of feeding arteries to the mass, for tumor stain, and for occlusion of either sigmoid sinus or transverse sinus. The mass was diagnosed as a giant osteoma, and was totally removed. The excised tumor measured 10 x 9 x 5 cm, and inspection at operation revealed it to be composed of a fragile osteoid portion and a comparatively soft connective tissue portion. The histological diagnosis of the mass was that it was a spongy osteoma including a comparatively large amount of connective tissue. The postoperative recovery of the patient was satisfactory and her dizziness disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)