Neuronavigation - methods and future perspective

With the recent developments in computer technology and the improvements in modern neuroimaging, frame-based stereotactic guidance for open microsurgi cal procedures has been increasingly replaced by neuronavigation, also call ed frameless stereotaxy. It allows transfer of individual patient's images onto the operative field to assist the neurosurgeon intraoperatively in def ining the tumor margins or identifying functionally important brain areas. The different localization techniques employed are articulated position-sen sing arms, infrared or ultrasound systems working with the principle of sat ellite navigation and robotic systems integrated with the operating microsc ope. In 200 operations performed with different systems (arm-based, robotic and infrared) the method proved to be helpful, enabling fewer invasive pro cedures to be performed. With a mean deviation of 2.87+/-1.9 mm for intraop erative localization, the accuracy was only slightly worse than in frame-ba sed stereotaxy with deviations below 2 mm. Neuronavigation was most helpful for operations on deeply seated lesions, skull-base tumors and lesions in brain areas with high functionality. The major disadvantage is the use of p reoperative data for navigation, leading to inaccuracies when anatomical st ructures are altered during the operation by resection of tumors or shift: of intracranial soft tissue. Intraoperative magnetic resonance imaging (MRI ) might be a solution for this problem. With the method of intraoperative M RI developed in our department it has already been possible to update neuro navigation with images reflecting intraoperative changes in anatomy. Theref ore, neuronavigation is definitely a method with growing importance in oper ative routine,and it will also spread into other surgical specialties.