A study on peritumoral brain edema around meningiomas by MRI and contrast CT.

In the present study upon 9 meningiomas, the volume of peritumoral brain edema was calculated by integration of the cross-sectional edematous areas on serial MRI slices. It was zero in 3 cases and ranged from 11 to 176.4 ml in the other cases. There was disruption of the cortex in all cases, ranging from slight to severe. T1 and T2 measurements were made at the level of maximum edema extension (at 1.5 T), using a mixed sequence. From the T2 values tissue water content in % was calculated using equations, which had been obtained by correlating water content with relaxation rates. These had been measured on human brain autopsy specimens subjected to hydration or dehydration. Assuming that spread of contrast agent marks the advancement of the front of edema produced by the tumor, calculation of the excess of edema production per unit tumor volume Veff/VN was performed on the basis of CT-studies made before, and at 1.5, 3 and 6 hr after contrast infusion. Of 6 tumors with edema (mean water content of peritumoral white matter of 91% and mean edema volume of 69.2 ml) the Veff/VN was 0.18-1.08 ml/h/cm3 tumor volume, whereas 3 tumors without associated edema had a Veff/VN of 0.03-0.12 ml/h/cm3. In meningiomas cortex penetration seemed to be a separate factor determining the spread of edema.