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 biochemical remission rates vary widely among different histological subtypes of pituitary adenoma. In this prospective study, we evaluated 107 consecutive primary pituitary adenomas operated on by a single surgeon including 28 corticotroph, 27 gonadotroph, 24 somatotroph, 17 lactotroph, 5 null cell, and 6 plurihormonal. In each case, we performed direct intraoperative inspection of the medial wall of the cavernous sinus which was surgically removed when invasion was suspected. This was performed irrespective of the functional status of the tumor. Medial wall resection was performed in 47% of pituitary adenomas, and 39 of 50 walls confirmed pathologic evidence of invasion rendering a positive predictive value of intraoperative evaluation of medial wall invasion of 78%. We show for the first time that the frequency 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 adenomas, 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 four 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 0.95 µg/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.