Predictive Value of Cavernous Sinus Invasion on Extent of Resection Following Endoscopic Transsphenoidal Resection of Pituitary Macroadenomas

Introduction: Cavernous sinus invasion is widely considered to be a significant determinant limiting extent of resection (EOR) following transsphenoidal removal of pituitary adenomas. Introduction of the endoscope to transsphenoidal surgery has enabled more panoramic visualization within the sella, allowing for potentially more complete resection of macroadenomas with cavernous sinus extension. In this study, we retrospectively assessed the frequency of gross total resection (GTR) of pituitary macroadenomas with cavernous sinus invasion as defined by the Knosp classification.

Methods: We retrospectively identified 77 patients with pituitary macroadenomas and cavernous sinus invasion with at least 1 year of postoperative clinical and radiographic follow-up. Cavernous sinus invasion was defined on coronal preoperative T1-weighted gadolinium-enhanced MRI according the Knosp classification. Extent of resection was defined based on postoperative MRI scans obtained within 1-3 days following surgical intervention and at approximately 3 and 12 months. The presence of residual nodular tissue within the intrasellar, suprasellar, or cavernous sinuses was considered a subtotal resection. The extent of resection for patients with cavernous sinus invasion was compared with a similar subset of patients over the same time period without cavernous sinus extension.

Results: Seventy-seven patients with pituitary macroadenomas with cavernous sinus invasion who underwent endoscopic transsphenoidal resection between 2006 and 2011 were identified. The primary pathologies included 68 nonfunctional adenomas, 7 growth hormone-producing adenomas, and 2 hemorrhagic prolactinomas. Tumor volume ranged from 0.66-94 cm³ (average, 13.3 cm³). Gross total tumor resection was achieved in 34/77 (44%) of patients overall with cavernous sinus invasion. Knosp grade significantly correlated with EOR. GTR was achieved in 12/17 (71%) patients with grade 1, 7/7 (50%) with grade 2, 13/25 (52%) with grade 3, and 2/16 (13%) with grade 4 cavernous sinus extension. Comparatively, over the same time period, GTR was achieved in 82% of patients with pituitary macroadenomas without cavernous sinus invasion.

Conclusions: Cavernous sinus invasion continues to significantly reduce the likelihood of complete surgical removal of pituitary macroadenomas. However, utilization of the endoscopic approach has enabled GTR to be accomplished in the majority of patients with Knosp grade 1-3 extension. Despite improved visualization, Knosp grade 4 cavernous sinus invasion remains associated with a persistently low rate of complete surgical resection.