Somatotroph Adenomas have a Predilection to Invade the Cavernous Sinus and Resection of the Medial Wall of the Cavernous Sinus Offers the Highest Potential for Biochemical Remission in Acromegaly

Abstract

Recurrence and remission rates vary widely among different histological subtypes of pituitary adenoma. Invasion of the medial wall of the cavernous sinus is a known mechanism that may account for such failed clinical outcomes as its removal has long been considered unattainable. The use of modern endoscopic techniques allows for direct intraoperative evaluation of invasion and resection of the medial wall of the cavernous sinus with low morbidity when performed by highly experienced surgeons. In this retrospective study we evaluated 105 consecutive primary pituitary adenomas operated by a single surgeon including 28 corticotroph, 27 gonadotroph, 24 somatotroph, 15 lactotroph, 5 null-cell, 5 plurihormonal, and 1 dual adenoma; 53 caused hypersecretory syndromes, specifically acromegaly (30), hyperprolactinemia (15) and Cushing’s disease (8). In each case, we performed meticulous intraoperative inspection of the medial wall with its surgical removal when invasion was suspected, regardless of functional status. Medial wall resection was performed in 46% of pituitary adenomas, and 38/48 walls confirmed pathologic evidence of invasion rendering a positive predictive value of intraoperative evaluation of medial wall invasion of 79%. Furthermore, we show for the first time that the rate of medial wall invasion among pathological subtypes is dramatically different. Somatotroph tumors invaded the medial wall much more often than other adenoma subtypes, 83% intraoperatively and 71% histologically, followed by plurihormonal tumors (40%) and gonadotrophs (33%), both with intraoperative positive predictive value of 100%. The least likely to invade were corticotroph, at a rate of 32% intraoperatively and 21% histologically, and null-cell adenomas at 0%. Removal of the medial wall caused no permanent morbidity with no carotid artery injuries and 2 patients with transient diplopia. We report that resecting the medial wall of the cavernous sinus in acromegaly offers the highest potential for biochemical remission with average postoperative day 1 GH levels at 0.96 ug/l and early surgical remission rates at 90% (100% with adjuvant therapy) based on normalization of IGF-1 levels 3 to 6 months after surgery; these results are significantly better than previously reported but longer follow-up is required for definitive conclusions. Our findings may explain the failed biochemical remission rates seen in acromegaly and illustrate the relevance of advanced surgical techniques for successful outcomes in pituitary surgery.