Difficulties in diagnosis of supratentorial gliomas by CAT scan.

The false positive and false negative computed tomography diagnoses of glioma made using an EMI 1010 machine on a consecutive series of patients seen over a period of two years are recorded. About 1.5% of gliomas were not detected on initial CAT scan, 6.5% were misdiagnosed as benign lesions, and in 6.5% of the cases identified as glioma a non-malignant condition was subsequently diagnosed.