Falcine Sinus and Parafalcine Collateral Veins in Meningiomas Invading the Superior Sagittal Sinus.

BACKGROUND:Venous collaterals form because of occlusion of the superior sagittal sinus (SSS), thus preserving venous drainage. Previous studies have focused on the evaluation and protection of sinuses and cortical veins and have neglected the collaterals between the SSS and deep venous system, which are important for surgical planning. We aimed to study the venous compensatory patterns inside and on both sides of the cerebral falx (parafalx) in patients with meningioma invading the SSS. METHODS:Conventional magnetic resonance imaging, magnetic resonance venography, and a three-dimensional reconstructed venous model of 45 patients were analyzed. The venous collateral pattern of the parafalx was divided into 4 types: A), with cerebral medial cortical vein displacement or hyperplasia; B), collaterals connect the 2 ends of the occluded segment of the SSS; C), collaterals connect the occluded segment of the SSS with the deep cerebral venous system; and D), recanalization or secondary formation of a falcine sinus. The incidence of each type in different occlusion grades and positions of the SSS was analyzed. RESULTS:The 4 types of venous collaterals were ranked according to their prevalence: A, 46.7%; C, 15.6%; D, 8.9%; and B, 4.4%. The collaterals of types B, C, and D were found only in patients with severe SSS occlusion, and both types C and D were found only in middle and posterior occlusions of the SSS. CONCLUSIONS:In meningiomas invading the SSS, especially with complete posterior SSS occlusion, the parafalcine collateral veins and falcine sinus should be evaluated preoperatively to avoid iatrogenic injury.