Cavernous sinus invasion by pituitary adenomas: role of endoscopic endonasal surgery

BACKGROUND: Cavernous sinus (CS) invasion is one of the most unfavorable features of pituitary adenomas. The most widely used classification was proposed by Knosp in 1993 and revised in 2015. The aim of this study is to extend our previous experience by comparing the preoperative neuroradiological assessment with the intra-operative endoscopic endonasal inspection in order to evaluate the real rate of CS invasion and analyze its correlation with the surgical outcome. METHODS: Consecutive patients, who have undergone endoscopic endonasal surgery for a pituitary adenoma with Knosp grade greater than 1, have been included in this study. The intra-operative CS invasion was assesses basing on surgical reports. The surgical outcome has been evaluated with MRI, endocrinological, visual and neurological evaluation have been performed 3 months after surgery and then annually. RESULTS: The series included 402 patients. Male-female ratio was 1: 1 and median age was 56 years (range 15-85). We observed that 43% of cases with Knosp grade greater than 1 presented no CS invasion on surgical inspection. Knosp grade 4 was the only one corresponding in all cases to a real CS invasion. Radical tumor removal was achieved in 60%. while endocrinological remission was obtained in 37% of functioning adenomas. Better results were observed for lower Knosp grades. CONCLUSIONS: The endoscopic endonasal inspection is the most effective technique to detect CS invasion. Indeed, it can provide a direct visualization of the medial wall, permitting the assessment of its invasion and the management of those cases with diffuse involvement. We confirm that the revision to the Knosp classification has improved its prognostic role.