Difficulties in diagnosis of intracranial meningiomas by computed tomography.

The false positive and false negative computed tomography diagnoses of meningioma made using EMI 1010 and 5005 machines on a consecutive series of patients seen over a period of four years are described. About 1.2% of intracranial meningiomas were not detected on initial CT scan, 6.6% were misdiagnosed including 5.2% which were thought to be malignant lesions; in 9.4% of the cases identified as meningioma another diagnosis was subsequently established of which 6.3% were malignant.