Brain scanning--cerebral scintigraphy. An evaluation of the diagnostic value or scanning compared with other methods of investigation, based on results from 981 patients

Computed tomography of supratentorial meningioma

The appearance on C.T. of 28 meningiomas is described. On the plain scan they presented as a rounded, well defined lesion with a high density in 18 cases and a density equal to or lower than brain tissue in 10 cases. The density could be related to certain histologic features as the amount of connective tissue and extracellular water and the presence of psammoma bodies or lipid storage cells. After administration of contrast a homogeneous, markedly increased, sharply marginated density was seen in most meningiomas. Contrast enhancement appeared to be dependent on the vascularity of the tumour. +/- 50% of the cases demonstrated edema grade II or III. On first interpretation 93% of the meningiomas were recognized as a lesion and a tumour (2 false negative) and 79% as a meningioma (2 false negative and 4 incorrect). Only one false positive C.T. scan was encountered. As a screening method R.N. scanning has about the same accuracy as C.T.; in establishing a definite diagnosis angiography equals C.T.; but C.T. is superior as it combines the diagnostic qualities of both methods.

Clinical reliability of posterior fossa scintigraphy

Radioisotope imaging of the brain is considerably less useful in posterior fossa lesions than in supratentorial diagnosis, due to the peculiar technical difficulties and biological characteristics of infratentorial lesions. Exceptions are acoustic neurofibromas and probably meningiomas, which can be reliably detected. The importance is stressed of making skull and chest radiographs at the time of the examination, in order to enhance the diagnostic accuracy of the scintigraphic result.

Scintigraphic diagnosis of acoustic neurofibromas

Radioisotope brain scanning gave positive results in 57 out of 68 acoustic neurofibromas in three British neurosurgical centres. Acoustic neurofibromas over 2 cm in diameter may be expected to give a positive scintigraphic result, and tumours of this size also erode the petrous bone. Since most are 3-4 cm in diameter, correlation between the results of petrous radiography and cerebral scintigraphy often permits a specific diagnosis of acoustic neurofibroma to be made. No other radiological investigation may be necessary preoperatively.