The value of the modified Knosp grade in pituitary adenoma surgery

Cavernous sinus invasion in pituitary adenomas, nowadays categorized with the modified Knosp grade, is strongly correlated with incomplete resection, lower rates of biochemical remission, and increased risk of recurrence. The aim of this study was to apply the modified KG to our institutional pituitary surgery cohort and to determine its association with gross total resection, serving as a contemporary external validation with an emphasis on interinstitutional reproducibility.

Prospectively collected data between 2011 and 2024 of patients with pure transsphenoidal endoscopic pituitary surgery in our tertiary academic referral center was analyzed. Uni- and multivariate regression models were applied to identify predictors for gross total resection.

A total of 482 patients were included in the study. Gross total resection was achieved in 69% of patients (grade 0: 97%, grade 1: 82%, grade 2: 79%, grade 3A: 45%, grade 3B: 35%, and grade 4: 7%). Multivariate logistic regression model showed that the modified Knosp grade remained the strongest independent predictor of achieving gross total resection.

In our cohort, the modified Knosp grade served as a reliable predictor of achieving gross total resection in pituitary adenoma surgery. The modification of Knosp grade 3 into 3A and 3B offers clear prognostic insights, since grade 3B demonstrates a significantly higher rate of incomplete resection. These findings serve as valuable information for determining treatment strategy and preoperative counseling for patients undergoing pituitary surgery.