Strategic Wide Arachnoid Release for Venous Mobilization in Transsulcal Parasagittal Surgery: Mitigating Vessel Wall Injury and the Gravity-Buoyancy Conflict (operative Technique and 2D Video).

Surgical resection of a single brain metastasis improves survival. However, lesions in the parasagittal perirolandic region pose a therapeutic challenge due to high eloquence and the "gravity-buoyancy conflict." Under physiological conditions, cerebrospinal fluid buoyancy reduces the brain's effective weight by approximately 95%. Loss of this support upon opening the dura leads to gravitational sag of the hemisphere. This increased functional weight pulls the bridging veins downward, creating a valve-like effect and a mechanical kink at the rigid dural entry point. A 59-year-old male presented with a 3-cm cystic metastasis in the posterior superior frontal gyrus (SFG). Intraoperatively, gravitational sag of the tumor-expanded gyrus created significant downward traction on the vein of Trolard. This tension induced a potential focal kink at the rigid dural interface, resulting in flow stasis, recognized by distal colorless depletion and dark, pulsatile proximal blood. Consent for the procedure and image publication was obtained, and Queen's University Ethics Board approved this report. Wide splitting of both the superior frontal and precentral sulci allowed for necessary safe access to the tumor and potential decoupling of the tumor-bearing SFG from the hemisphere. To resolve the dural entry kink, a strategic wide arachnoid release was performed along the vein to provide vascular laxity. After early cyst drainage and unloading the pathological weight, the created laxity allowed the vein to return to its physiological location, resolving the stasis. Untethering the vein from its arachnoid anchors allowed the vein to tolerate necessary traction on the vessel wall during tumor resection ( Video 1 ).