Rachid Kamouni

The Mirroring Technique: A Navigation-Based Method for Reconstructing a Symmetrical Orbit and Cranial Vault

BACKGROUND: The reconstruction of orbital structures and the cranial vault curvature can be challenging after trauma or wide resections for tumors. Sophisticated methods have been developed recently, but these are resource- and time-consuming. OBJECTIVE: We report the mirroring technique, which is an effective and costless application for navigation-guided reconstruction procedures. METHODS: At the time of the reconstruction, high-resolution images are reloaded while forcing a left-right axial flip. The pointer subsequently enables a virtual 3-dimensional projection of the position of the contralateral normal anatomy. RESULTS: This method was applied successfully in 2 cases of en plaque sphenoid wing meningiomas with secondary exophthalmia. CONCLUSION: The mirroring technique represents an accurate method of outlining the contralateral normal anatomy onto the pathological side based on navigation guidance.

Simultaneous Image-Guided Skull Bone Tumor Resection and Reconstruction With a Preconstructed Prosthesis Based on an OsiriX Virtual Resection.

BACKGROUND: Skull reconstruction can be challenging due to the complex 3-dimensional shape of some structures, such as the orbital walls, and for cases involving a large cranial vault. In such situations, computer-assisted design and modeling of prostheses is especially helpful to achieve an adequate reconstruction. Simultaneous tumor resection and skull defect reconstruction are also challenging because the preoperative imaging does not display the anticipated defect. Currently, sophisticated methods based on physical prototypes and templates are required to enable simultaneous resection and reconstruction techniques. OBJECTIVE: To report a new technique for simultaneous tumor resection and skull reconstruction with a custom-made prosthesis. METHODS: Using OsiriX software, virtual bone resection was performed using preoperative images by carefully delimiting the tumor on each slice. The modified images were integrated to predict the defect and also served as a basis for prosthesis construction. At the time of surgery, the images were projected onto the patients skull using a surgical navigation system to delimit the area of the craniectomy. RESULTS: The virtual planning method was simple and accurate and provided a precise preoperative definition of important structures that needed to be spared, such as the frontal sinus. Using this method, simultaneous tumor resection and prosthetic skull reconstruction was successfully achieved for a patient with a wide skull tumor. CONCLUSION: Simultaneous skull tumor resection and prosthetic reconstruction are possible when a virtual preoperative tumor resection is performed, and a corresponding customized prosthesis subsequently is manufactured and used. ABBREVIATIONS: ROI, region of interest

A neuronavigation-based method for locating the superficial temporal artery during extra-intracranial bypass surgery

The superficial temporal artery (STA) is frequently used as donor vessel in extracranial to intracranial bypass surgery. Current techniques typically rely on a Doppler vascular probe to identify the STA trajectory prior to the skin incision; however, this step can be time consuming and difficult when the arterial course is tortuous. We tested an alternative neuronavigation-based technique for locating the STA. In this method, preoperative magnetic resonance angiography (MRA) or computed tomography angiography (CTA) was used to determine STA outlines that were then projected and traced onto the skin. The neuronavigation-based technique was applied to eight STA dissections. The accuracy of this method was evaluated by comparing the navigation-based STA course with the doppler-based one and the actual STA course intraoperatively. STA trajectory was determined before surgery by using three imaging techniques: CTA (3 cases), three-dimensional (3D) contrast-enhanced T1-weighted MRA (4 cases), and/or 3D time-of-flight MRA (5 cases). In all cases, the neuronavigation-based STA position was confirmed with the Doppler vascular probe before skin incision and corresponded to the actual vessel position intraoperatively. As long as the skin is not mobilized during preoperative image acquisition and surgery, this neuronavigation-based approach is a valid method to identify STA course. During the preoperative planning process, the STA trajectory should be analyzed from its origin at the level of the foramen spinosum to avoid mistaking nearby venous structures as the STA.