Nature Abhors A Cavity: The Relationship Between Intradural Dead Space and Risk of Cerebrospinal Fluid Leak Following Resection of Olfactory Groove Meningiomas

Background: Rates of cerebrospinal fluid (CSF leak) following endoscopic endonasal resection of olfactory groove meningiomas (OGM) range between 10-30% and remain a significant challenge in managing these tumors due to the propensity for further morbidity. Despite improvements in reconstructive techniques with multilayer reconstruction and vascularized flaps, persistent CSF leak remains a troublesome complication. Objective: The authors aim to determine whether increased tumor volume, and subsequently greater intracranial dead space following resection, is associated with an increased risk of post-operative CSF leak. A secondary aim is to identify high-risk patients and propose adjustments to the reconstructive algorithm to prevent postoperative CSF leak. Methods: This is a retrospective case series at a single institution. All patients who underwent EEA for OGM between 2014-2025 who had imaging available for review were included. Pre-operative MRI was reviewed to measure maximal tumor dimensions in anterior-posterior (AP), lateral (L), and cranial-caudal (CC) dimensions. Post-operative CT head was used to measure AP and L dimensions of the bony defect, as a proxy for the dural defect. Other perioperative details were reviewed including lumbar drain usage, initial reconstructive technique, and management of any post-operative leaks. Univariate analysis was performed. Results: 53 patients met inclusion criteria. The overall CSF leak rate was 21.1%. 51 patients were reconstructed with a dural substitute inlay, a fascia lata only, and a nasoseptal flap. 1 patient was reconstructed with a pericranial flap, and 1 patient was reconstructed with temporalis fascia. Gross total resection was achieved in 34 patients. 14 patients had a subtotal resection with >90% of tumor resected, and 4 patients had partial resections with