The Role of the Expanded Endoscopic Endonasal Approach in Staged Surgery for Giant Olfactory Groove Meningioma: Technical Nuances

Background Giant olfactory groove meningiomas (OGMs) are unique tumors that present a formidable challenge to skull base surgeons. They are highly vascular lesions, deriving their main blood supply from the anterior and posterior ethmoidal arteries. Each skull base approach and technique have advantages and limitations that must be considered when selecting the optimum treatment plan for each patient. Craniotomies are limited when dealing with severe brain edema, reaching the tumor blood supply, hyperostosis of the skull base, and sinonasal invasion. Endoscopic endonasal approaches (EEAs) are limited reaching lateral meningioma implantation. Therefore, planning the surgical strategy to attack these tumors while achieving the optimum outcome with minimal complications is demanding.

Objective To review tour experience with a cohort of patients who underwent a two-stage approach for the surgical management of giant OGM. We aimed to delineate the advantages, drawbacks, and surgical nuances of combining different approaches for the staged resection of OGM.

Results We present four cases with OGM for whom a two-stage surgery was performed. EEA was performed as a first-stage procedure in all the cases. Early devascularization of the tumor was achieved, allowing the second-stage surgery to be performed on a devitalized residue. The second stage was performed after 2 to 12 months later. The timing for the second stage was based on vision and cognitive outcome after EEA stage. A right or left lateral fronto-orbital craniotomy was performed in all cases depending on tumor configuration. A right-sided approach was used on symmetric cases. The brain was very relaxed in all cases and the tumor was basically devascularized. Microsurgical technique was used to accomplish a total resection with exception of one case where the decision was to leave tumor around the anterior cerebral arteries. Radiation was applied to the only patient with residual tumor. EEA allowed for optimum drilling of the hyperostotic skull base bone, and complete resection of any tumor in the sinonasal cavity and the dural attachment of the tumor. EEA allowed for internal debulking of the tumor while obviating brain retraction.

Conclusion Patients with giant OGM with significant frontal lobe edema, sinonasal invasion, and/or skull base hyperostosis seem to benefit the most from this strategy. In our opinion, EEA should be considered as a first-stage procedure in select cases of giant OGM; however, larger multicentric case series should be conducted to further validate our experience.