Frameless image-guided neuronavigation in orbital surgery: practical applications.

Frameless neuronavigation has been increasingly used in intracranial and spinal neurosurgery. However, the application of neuronavigation in orbital surgery has not yet been reported. The purpose of this study was to evaluate whether frameless navigation in the orbit provides sufficient clinical application accuracy and thus a useful tool in orbital surgery. A frameless infrared-based neuronavigation system (VectorVision, BrainLAB, Heimstetten, Germany) was used in the microsurgical removal of 11 orbital tumors (five cavernomas, three lymphomas, two dermoid tumors, and one rhabdomyosarcoma). The transconjunctival approach was performed in seven cases, lateral orbitotomy in three cases, and the extradural pterional approach was performed in one case. The surgery was successful and without any complications in all cases. The registration accuracy of the neuronavigation was between 1.8 and 2.2 mm, with a mean of 1.9 mm. Subtotal tumor debulking was performed in one case with lymphoma. One patient was only biopsied due to suspected systemic lymphoma disease. Total removal of the tumor could be accomplished in the other nine patients. Image guidance during orbital surgery offered excellent three-dimensional guidance on the surface of the intraorbital lesions, allowing a safer, more controlled surgery. The surgical targets in the orbit are fixed structures, thus no shifting occurs and continuous high intraoperative navigation accuracy can be achieved. The use of the navigation clearly reduces the operative risk and increases the effectiveness of microsurgical orbital procedures.