The significance of morphological changes in the brain-tumor interface for the pathogenesis of brain edema in meningioma:: Magnetic resonance tomography and intraoperative findings.

Purpose: The aim of the study was to verify a possible correlation between macroscopic changes of the brain-tumor interface (BTI) and the development of a peritumoral brain edema in meningiomas. Methods: 27 meningiomas were investigated in this prospective study using an optimized inversion-recovery (IR) sequence. After i.v. administration of 0.2 mmol Gd-DTPA/kg axial and coronary images were acquired (slice thickness=2 mm). The distances of signal altered cortex and obliterations of the subarachnoid space (SAS) were measured at the BTI and related to the pial tumor circumference (cortical-index and SAS-index). Intraoperatively the BTI was divided into the following categories: 0: SAS not obliterated, 1: SAS partially obliterated, 2: direct contact between tumor and white matter, 3: tumor infiltration into brain. Results: Edema-associated meningiomas showed a significantly (p = 0.0001) increased SAS-index (0.47 vs. 0.07) and cortical index (0.45 vs. 0.0) compared to cases without edema. Intraoperatively 95% of meningiomas with brain edema showed SAS-obliterations, compared to 50% of cases without an edema. Conclusions: Arachnoid adhesions at the BTI with obliteration of the SAS seem to play an essential role in the induction of brain edema in meningiomas.