The radiological diagnosis of meningiomas, the impact of EMI scanning.

A review of the impact of computerized axial tomography on the radiological diagnosis of meningiomas is presented. Seventy-one intracranial and eight orbital cases have been examined by this new method using the 160 X 160 matrix. The diagnostic accuracy of the method is compared with established neuroradiological methods of examination (plain X rays, angiography, pneumography and isotope scanning). The new non-invasive method is undoubtedly the most accurate diagnostic tool yet available. It provided a specific diagnosis of meningioma in 77% of the intracranial cases without contrast enhancement and diagnosed the presence of tumour in a further 19% giving an overall tumour diagnosis of 96%. There were three false negatives (4%). After intravenous injection of contrast medium specific diagnosis of meningioma was made in a further six cases raising the specific diagnostic rate to 86%. Specific identification of intra-orbital meningiomas is more difficult though the presence of retro-orbital tumour was correctly diagnosed in all eight cases examined (100%). In none of our cases was a false positive diagnosis of tumour made. However, there are areas where a specific diagnosis of meningioma can only be made as part of a wider differential diagnosis. Apart from the orbit these include the suprasellar area, the cerebello-pontine angle, and the intraventricular regions. Occasionally also supratentorial gliomas or secondaries can simulate meningiomas.