Intracranial epidermoids--concerning the low absorption value on computerized tomography.

The authors analysed the contents of two intracranial epidermoids showing low density on computerized tomography. Although both cases had approximately similar composition, 85, 83% for water, 12, 12.5% for protein, 3, 4.5% for total lipid including cholesterol, respectively, the absorption values differed from each other. Both tumours were identified to communicate with CSF, one by delayed metrizamide CT scan and the other by direct aspiration during operation. The low absorption values in both cases resembled or were slightly higher than that of CSF in each case, and not a single pixel showed negative values for lipid. These findings suggest that it is the CSF content within the anatomical interstices or structural crevice of the tumour, rather than cholesterol, which is responsible for the low absorption values which appeared in the CT scan.