Resolution of peritumoral brain edema following excision of meningioma.

We studied the resolution of peritumoral brain edema after meningioma excision. In twenty-nine patients with meningioma, the total volume of tumor and the peritumoral edema were measured planimetrically by serial CT scans and MRI with or without contrast enhancement. Four different patterns of postoperative resolution of hypodense volume on CT were observed: Group A: a large hypodensity rapidly decreased and disappeared, which may be related to the clearance of the real peritumoral edema in meningioma. Group B: a small hypodensity gradually disappeared. Group C: the hypodensity remained unchanged, which may result from the damaged brain tissue. Group D: the hypodensity progressively decreased but persisted, which may represent both the peritumoral edema and damaged brain tissue. We have calculated the resolution rate of edema fluid using the clearance curve of Groups A and D. The average resolution rate of edema fluid during the passage through 1 cm3 of the peritumoral white matter was 0.0493 ml/day. We speculate that 50% of edematous white matter, which presented as hypodensity on a CT scan, may be resolved in 4 days after total removal, and that 90% may be resolved in 14 days.