OBJECTIVE

This study aimed to examine the reliability of existing Knosp grade (KG) and modified KG for cavernous sinus invasion (CSI).

METHODS

A thorough search of literature from 1993 to 2020 in six databases was performed. Studies that reported the intraoperative confirmation of CSI using KG and/or modified KG were included. The pooled estimates were calculated by meta-analysis with a bivariate mixed-effect model and the assessment of heterogeneity with I statistic.

RESULTS

The final search yielded 12 eligible studies, which enrolled 3006 patients assessed with KG and 1315 patients assessed with modified KG. The results of the area under the receiver operating characteristic curve showed the good discriminative abilities of grades 2-4 (0.90), 3-4 (0.86) and 3B-4 (0.91) in predicting CSI. Grade 3A showed a remarkably lower CSI rate (44% versus 81%) and incomplete resection rate (26% versus 52%) than grade 3B. Grades 0 and 1 showed a low CSI rate. CSI and incomplete resection rates in grade 2 (30% and 21%, respectively) were close to those in grade 3A.

CONCLUSIONS

Modifying the KG improved its prognostic role in CSI and gross total resection. However, these grading systems cannot be used as the group standard for invasive and non-invasive pituitary adenomas (PAs) because of the weak reliability of the scale's middle grades (grades 2 and 3A). Authors of future PA studies should consider reporting KG as high (grades 3B and 4), medium (grades 2 and 3A) and low (grades 0 and 1) to optimise the application of the scale.