OBJECTIVETo evaluate the utility of performing transsphenoidal surgery with computer-assisted image guidance.METHODSThirty-seven patients underwent transsphenoidal surgery in which a frameless stereotactic system was used to confirm the trajectory to the sella and to locate the anatomic midline. This technique was compared with our standard method of using an image intensifier to confirm the approach (n = 43). The numbers of complications associated with the approach, the times required to set up and perform each operation, and the average costs for each group were compared.RESULTSThere were no complications attributable to inaccurate localization from the neuronavigational system. Additional setup time was necessary to calibrate and register the system; this represented a mean of 17 minutes in transsphenoidal procedures performed for the first time (n = 30), whereas reoperations required an average of 22 minutes (n = 7) (P< 0.05). The operative times, defined as time from incision to closure, were not statistically different (P= 0.38). To reduce assistant variation, a subset of this group in which the same assistant was used (n = 18) was analyzed. The additional setup time was reduced to a mean of 12 minutes (P< 0.05). The total case times were actually reduced in this group (127 versus 133 min), but this was not statistically significant (P= 0.75). Fluoroscopy was not required when frameless stereotaxy was used. The cost savings were partially offset by the cost of the preoperative computed tomographic study necessary for fiducial registration and the additional cost of setup time in the operating room. When all factors were analyzed, an additional cost to the patient of $318.00 was noted. The image guidance in axial, coronal, and sagittal planes provided by frameless stereotaxy was subjectively beneficial; it increased our confidence with the approach to the sella and intraoperative localization and was particularly helpful in reoperations where standard anatomic landmarks were distorted.CONCLUSIONFrameless stereotaxy is a technology that provides continuous, three-dimensional information for localization and surgical trajectory to the surgeon and can be applied to transsphenoidal surgery with minimal additional cost and time requirements.