L．CHANGHoNG．C．NAlYIN．G．YUEHUAN and Z．LIANZHONG<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Department of Radiology，Guangdong Provincial Hospital，Guangdong. China

Accepted for Publication 29 octobet 1996

Meningioma constitutes 14％ to 20％ of intracranial neoplasms^[1]．Sites of predilection directly correlate with abundant arachnoid granulations and Iess than l％ are extradual intraosseous：parasagittal and falx(5％), convexity (18％)，sphenoid ridge(18％)，olfactory groove (12％), parasellar (12％), posterior fossa (10％), intraveventicular (2％), intraorbital (1％)^[2] and extradural tissues (1％)^[3]. Extradural tissue includes the skin, the neck, the paranasal sinuses, the nasal cavities and the diploe of the cranial bones ^[3-5]. The intraosseous tissue refers to the diploe of the cranial bones.

Plain skull radiographs can detect abnormalities in 30％ to 60％ of cases, including hyperostosis, thinning of bone, speckled or granular calcification and prominent vascular markings. Angiography demonstrates the presence of symptomatic meningiomas in 95％Of patients and may permit accurate pre-operative diagnosis of meningioma in 70％of patients ^[3]. The characteristic features include vascular blush as homogeneous sharply maginated opacification and regularly aligned tumour vessels of similar sized calibre^[3].

Most meningiomas on CT are homogeneously solid tumours, but foci of necrosis and scarring, cystic degeneration, or areas of heavy lipid storage are identified in 15％. After administration of intravenous contrast medium，there is typically a striking degree of homogeneous enhancementof the tumour mass.