Navigational guidance in transsphenoidal pituitary adenoma surgery

Objective: To assess whether frameless stereotaxy can further increase safety and efficacy of transsphenoidal microsurgery.Methods: We conducted a retrospective analysis of 29 patients with pituitary adenomas (10 recurrent, 12 micro, 17 macro), who had undergone image guided endonasal transsphenoidal surgery during an 18-month period in the Department of Neurosurgery, Medical University - Sofia, Bulgaria. In the preoperative planning process, the adenoma volume and both carotid arteries were segmented in a MRI/CT-3 D dataset (T1-weighted, 3 D FLASH after Gadolinium). An optical infrared-based neuronavigation system (Vector Vision, BrainLAB®, Heimstetten, Germany) was used in all cases for frameless guidance. Using Z-touch infrared markerless or landmark registration (in 3 cases) a mean calculated accuracy of 1.47±0.4 mm was achieved; intraoperative accuracy was checked every 10 min. Intraoperative records were reviewed with attention to the utility of the navigational guidance.Results: The time requirements for set-up, registration and navigational control were minimal (<16 min). In none of the cases the system did interfere with surgical manipulations. True accuracy at surgery was obtained in 29/30 cases. A mean calculated accuracy of 1.47±0.4 mm was achieved during co-registration (1.45±0.69 mm for MRI-based NN and 1.53±0.64 mm for CT-based guidance), which is in concordance with the data from the literature, using similar navigational system , . The frameless technique was used to determine the midline, the depth and trajectory of the approach, as well as to reduce safely working area (in 29/29); in later stages, it provided fast and correct anatomical orientation in relation to the perisellar structures (24/29). Guidance was especially useful in asymmetrical/atypical microsella (in 9/9 pts), in conchal type of sella (3/3 cases), and helpful in locating accurately eccentric microlesions. Conclusions: We found frameless guidance during transsphenoidal surgery useful in certain occasions: misleading sphenoidal sinus anatomy, narrow/asymmetrical sella, eccentric adenomas with perisellar extension/distortion and re-operations for recurrent/residual tumors with obscured bony landmarks. In macroadenomas, however, the accuracy and reliability of the technique are compromised after debulking due to movements of the adenoma capsule