LED auto registration in navigated endoscopic-transnasal pituitary surgery of microadenomas

Abstract

Background: In transsphenoidal pituitary surgery computer aided surgery (CAS) is a generally accepted method. However, there are basic problems with the constancy of accuracy without mayfield fixation as well as with extended referencing time. In pure endoscopic-transnasal surgery it is not only useful to have information about the sella region and its adjacent structures but also to manage the rhinosurgical part of the approach. Especially for identification and removal of hormonally active microadenomas the combination of both, neuronavigation and endoscopy, is a useful method to achieve complete removal of the adenoma. Only the combination of CT and MRI reveals the necessary information for a successful intraoperative management with detailed information about the bony structures of the inner nose and the skull base (CT) and clear delineation of the soft tissue, especially the sellar content (MRI). Material and method: The endoscopic procedures were performed using a standard STORZ endoscopy system with a wide range optical system. During the procedure the tip and direction of the endoscope are tracked by the navigation system. On the navigation screen the video image of the endoscope and the position of the navigated endoscope in the image data set (matched CT/MRI) is displayed in real time. Together with our working group the navigation system manufacturer (Stryker-Leibinger) developed a non-invasive, frameless, automatic patient registration and simultaneous tracking system for navigated endoscopic-transsphenoidal surgery. The tracking and navigation system consists of an active, LED-based, self-adhesive foil attached to the surface of the face. This LED autoregistration mask was used in 10 patients regarding manageability, applicability and accuracy. Results: With this method a fast marker free automatic patient registration could be achieved. The intraoperative accuracy of the navigation system was constantly around 1mm in the region of interest. The registration mask allowed real time patient tracking while the patients head was mobile. Because the position of the endoscope was constantly tracked and visualized orientation was optimally supported to identify the regions of risk and interest. This technique allowed a fast and accurate transit through the inner nose into the sphenoid sinus in all patients. The operation time could be reduced by 30min in average. In cases of hormonally active (GH, PRL, ACTH) microadenomas the localisation of the adenoma was simplified. Conclusions: Navigated endoscopic-transnasal pituitary surgery of microadenomas using the LED autoregistration mask is an outstanding technique that allows a fast and accurate approach directly through the inner nose to the region of interest. Especially the resection of hormonally active microadenomas can be optimized to achieve full remission of the hormone excess while anterior pituitary function can be preserved.