Background: This study used high-resolution magnetic resonance (MR) imaging (1.5 T) to define and evaluate preoperative imaging criteria for cavernous sinus invasion (CSI) by pituitary adenoma (PA).
Methods: Magnetic resonance images obtained from 103 patients with PA submitted to surgery (48 with CSI) were retrospectively reviewed. The following MR signs were studied and compared with intraoperative findings: (1) presence of normal pituitary gland between the adenoma and cavernous sinus (CS), (2) status of the CS venous compartments, (3) CS size, (4) CS lateral wall bulging, (5) displacement of the intracavernous internal carotid artery (ICA) by adenoma, (6) grade of parasellar extension (Knosp-Steiner classification), and (7) percentage of intracavernous ICA encased by the tumor. Statistical analysis was performed using chi2 testing, and sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were obtained for each MR finding. The odds ratio of the most significant criteria was also obtained, and the multiple logistic regression test was used to compare the criteria altogether.
Results: The following signs have been found to represent accurate criteria for noninvasion of the CS: (1) normal pituitary gland interposed between the adenoma and the CS (PPV, 100.0%), (2) intact medial venous compartment (PPV, 100.0%), and (3) percentage of encasement of the intracavernous ICA lower than 25% (NPV, 100.0%). Cavernous sinus invasion was certain if the percentage of encasement of the intracavernous ICA was higher than 45% and 3 or more CS venous compartments were not depicted. The most valuable criterion of CSI by logistic regression analysis was the percentage of encasement of intracavernous ICA of 30% or more, with an odds ratio of 49.25.
Conclusion: The preoperative diagnosis of CSI by PA is extremely important because endocrinologic remission is rarely obtained after microsurgery alone in patients with invasive tumors. The aforementioned MR imaging criteria may be useful in patient's management and in advising most of the patients preoperatively on the potential need for complimentary therapy after surgery.