Incidence and Significance of Intraoperative CSF Leak in Endoscopic Pituitary Surgery Using Intrathecal Fluorescein

Introduction: The true rate of intraoperative (i)CSF during pituitary surgery is not well known because small iCSF leaks are easily missed as clear fluid mixed with blood can be difficult to detect.

Objectives: We administered intrathecal fluorescein preoperatively in a large series of pituitary adenomas to determine the rate and significance of iCSF leaks.

Methods: The appearance of intraoperative fluorescein was noted prospectively in a consecutive series of 203 patients undergoing endonasal endoscopic resection of their pituitary adenomas. The rate of iCSF leak was correlated with tumor diameter (all cases), tumor volume (160 cases), rate of gross total resection (GTR), the learning curve (first 50 cases), reoperation, and hormone production. Rate of postoperative CSF leak, complications from fluorescein and utility of the nasoseptal (NS) flap in preventing postoperative leaks was also noted. Chi-square and Fisher exact tests were used for significance.

Results: In the entire cohort, rate of iCSF leak was 61%. Tumor diameter and volume were strong predictors. The iCSF leak rate ranged from 44% for tumors <2 cm to 72% for tumors ≥2 cm (P < 0.001). It was 35% for tumors <1.5 cm³ and 68% for tumors ≥1.5 cm³ (P < 0.001). The rate of GTR and the learning curve did not influence the rate of iCSF leak. Reoperations had a higher rate of iCSF leak but only for tumors >2 cm. Postoperative CSF leak was significantly lower once the learning curve was passed (0.7% versus 10%; P < 0.005). For tumors >2 cm, the introduction of the NS flap reduced the CSF leak rate from 5.6% to 1.4 %. We did not find any complications related to the use of intrathecal fluorescein.

Conclusions: Using intrathecal fluorescein, we determined that the rate of iCSF leak may be higher than previously suspected. Tumor diameter and volume are the best predictors of the risk of iCSF leak. Based on this knowledge and a consistent algorithm for closure, which can include lumbar drainage and the NS flap for larger tumors (>2.5 cm), the rate of postoperative CSF leak remains exceptionally low, particularly once the learning curve is overcome.