Cystic intracranial tumours. Cyst fluid, biochemical changes and computerised tomographic findings.

The concentrations of five biochemical substances were studied in cyst fluid from 49 cystic intracranial tumours and the findings were compared with the computerised tomographic (CT) scan and histological appearances of the tumours. The attenuation of the cyst wall on unenhanced CT was found to be related to cyst fluid alkaline phosphatase levels. Enhancement of the cyst wall with contrast medium was associated with higher levels of protein, cholesterol, alkaline phosphatase, phosphohexose isomerase (PHI) and lactate dehydrogenase (LDH) in the cyst fluid. Lesions of high grade malignancy had higher levels of protein, cholesterol, alkaline phosphatase, LDH and PHI than lesion of low grade malignancy and also higher levels of alkaline phosphatase, LDH and PHI than benign lesions. Oedema around a lesion was associated with increased malignancy.