“Pseudocapsular” Resection of Pituitary Adenomas: Technical Nuances and Unexpected Consequences

Introduction: Following a visit to our institution in June 2010 by Edward Oldfield, we began a more diligent pursuit of the use of the so-called pseudocapsule to excise pituitary tumors. We were at first frustrated in the inability to identify the pseudocapsule plane in the vast majority of patients. Over a period of 8 months, however, we were increasingly successful in developing the pseudocapsule plane, eventually achieving it in more than 40% of cases. An unexpected consequence was a drop in the intraoperative CSF leak rate.

Methods: In this retrospective analysis, medical records and operative videos were reviewed of 189 consecutive pituitary adenoma operations using the combined neurosurgery-otolaryngology endoscopic endonasal resection approach from April 2008 to September 2011. The percentage of successful pseudocapsular dissections—defined as circumferential dissection of the tumor maintaining near complete integrity of the tumor “capsule” that was in contact with normal pituitary tissue—was determined on a quarterly basis, along with incidence of intraoperative CSF leaks. Over the last three quarters, the resection technique evolved significantly, more closely resembling standard techniques for resection of meningiomas.

Results: Prior to the third quarter of 2010, the average quarterly intraoperative CSF leak rate was 39 ± 10%, with only one pseudocapsular dissection accomplished among 109 patients (1%). Over the next two quarters, pseudocapsular dissection was possible in 8% of cases, but the intraoperative CSF leak rate remained at 33%. Over the subsequent three quarters, successful pseudocapsular dissection increased to 42%, with the intraoperative CSF leak rate dropping to 13%. There has been only one intraoperative leak among the last 23 cases (mean tumor size, 21 ± 12 mm; gross total resection rate of 81%).

Conclusion: A surgical approach of initially identifying and developing the tumor-gland interface, centrally debulking tumor as needed and then completing the pseudocapsular dissection circumferentially, allows earlier and easier visualization of key normal structures. In our experience, this has significantly reduced the number of incidental tears of the diaphragm sella/arachnoid membrane, while maintaining (enhancing) the ability to remove all tumor tissue.