Original Contributions Computer-Assisted Intraoperative Navigation During Skull Base Surgery Ricardo L. Carrau, MD, Carl H. Snyderman, MD, Hugh D. Curtin, MD, Ivo I? Janecka, MD, Michael Stechison, MD, PhD, and Jane L. Weissman, MD Purpose: In patients with diseases of the cranial base, anatomical landmarks are often obliterated by tumor inflammatory diseases or previous surgery. The surgeon may fail to recognize important anatomical structures or tumor margins, increasing the morbidity of the surgery and downgrading the oncological outcome. Materials and Methods: The ISG Viewing Wand is an intraoperative navigational device that uses a position-sensing articulated arm linked to a computer that allows the surgeon to correlate the anatomy of the patient with the computerized display of the reformatted images of preoperative computerized tomography or magnetic resonance. We used the ISG system in 20 patients undergoing skull base surgery for the treatment of tumor inflammatory diseases and trauma. Results: The use of the ISG wand translated into a decreased need for the resection of vital structures and provided reliable mapping of the boundaries of the paranasal sinuses and tumor margins. Conclusion: Intraoperative navigation is a promising technology that complements the surgeon’s interpretation of the surgical field. Further refinements of this technology will ease the incorporation of these intraoperative navigation systems into other surgical procedures. Copyright 0 1996 by W.B. Saunders Company. In patients with diseases of the cranial base, anatomical landmarks are often obliterated by tumor, inflammatory diseases, or previous sur- gery. Failure to recognize anatomical struc- tures or tumor boundaries increases the mor- bidity of surgery and the potential for incomplete tumor resection. Intraoperative navigation is a promising technological advance that can assist the sur- geon in identifying landmarks that are not From the Departments of Otolaryngology, Radiology, and Neurolooical Suroerv, Universitv of Pittsburah School of Medicine,Pittsburgh, PA. . Supported in pan by The Mary Hillman Jennings Foundation and The John R. McCune Charitable Trust Foundation. The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of the above foundations. Address reprint requests to Ricardo L. Carrau, MD, Assistant Professor, Department of Otolaryngology, Uni- versity of Pittsburgh School of Medicine, 203 Lothrop St, Ste 500. Pittsburah, PA 15213. Copyright 0 1996 by W.B. Saunders Company 0196-0709/96/i 702-0004$5.00/O easily visualized, therefore facilitating the ex- tirpation of tumors in deep and complex ar- eas.1-8 The ISG Viewing Wand (ISG Technolo- gies, Toronto, Ontario, Canada) uses a position- sensing articulated arm linked to a computer that displays reformatted images of preopera- tive computerized tomographic (CT) or mag- netic resonance imaging (MRI) scans, allowing the surgeon to correlate the anatomy of the patient with the computerized display (ie, real-time visual feedback). We present our experience with the use of the ISG intraoperative navigational device dur- ing skull base surgery. The advantages and disadvantages of the system are discussed. METHODS From June 1992 to June 1994, we used the ISG navigational system on 20 patients requiring sur- gery of the skull base (Table 1). Selection of patients was based on the complexity of the case and the availability of the Viewing Wand. American Journal of Otolaryngology, Vol 17, No 2 (March-April), 1996: pp 95-l 01 95