Knosp et al offered a grading system for showing invasion of cavernous sinus by pituitary macroadenoma. Briefly, the much laterally adenoma grows and surrounds the ICA, the more grade level is. The grading defined by the relation of carotid lines with the limits of invasion. These lines passes through supra- and intra-cavernous parts of ICA in coronal view. There are medial, median and lateral carotid lines.
- grade 0: adenoma does not extend the medial carotid line
- grade 1: adenoma extends the medial line, but doesn't reach the median line, so-called "intracarotid" line
- grade 2: tumor extends beyond the median line, but doesn't extend beyond or tangent to the lateral line
- grade 3: tumor extends beyond the lateral line
- grade 4: tumor totally wraps around the intracavernous carotid artery