A three-dimensional computer-based perspective of the skull base.

OBJECTIVE: To describe our designed protocol for the reconstruction of three-dimensional (3D) models applied to various endoscopic endonasal approaches that allows performing a 3D virtual dissection of the desired approach and analyzing and quantifying critical surgical landmarks. METHODS: All human cadaveric heads were dissected at the Laboratory of Surgical Neuroanatomy of the University of Barcelona. The dissection anatomic protocol was designed as follows: 1) virtual surgery simulation systems, 2) navigated cadaver dissection, and 3) postdissection analysis and quantification of data. RESULTS: The virtual dissection of the selected approach, the preliminary exploration of each specimen, the real dissection laboratory experience, and the analysis of data retrieved during the dissection step provide a complete method to improve general knowledge of the main endoscopic endonasal approaches to the skull base, at the same time allowing the development of new surgical techniques. CONCLUSIONS: The methodology for surgical training in the anatomic laboratory described in this article has proven to be very effective, producing a depiction of anatomic landmarks as well as 3D visual feedback that improves the study, design, and execution in various neurosurgical approaches. The Dextroscope as a virtual surgery simulation system can be used as a preoperative planning tool that can allow the neurosurgeon to perceive, practice reasoning, and manipulate 3D representations using the transsphenoidal perspective acquiring specifically visual information for endoscopic endonasal approaches to the skull base. The Dextroscope also can be used as an advanced tool for analytic purposes to perform different types of measurements between surgical landmarks before, during, and after dissection.

Anatomic skull base education using advanced neuroimaging techniques.

OBJECTIVE: The goal of the present article was to describe our dissection training system applied to a variety of endoscopic endonasal approaches. It allows one to perform a 3D virtual dissection of the desired approach and to analyze and quantify critical surgical measurements. METHODS: All the human cadaveric heads were dissected at the Laboratory of Surgical Neuro-Anatomy (LSNA) of the University of Barcelona (Spain). The model surgical training protocol was designed as follows: 1) virtual dissection of the selected approach using our dissection training 3D model; 2) preliminary exploration of each specimen using a second 3D model based on a preoperative computed tomographic scan; 3) cadaveric anatomic dissection with the aid of a neuronavigation system; and 4) quantification and analysis of the collected data. RESULTS: The virtual dissection of the selected approach, preliminary exploration of each specimen, a real laboratory dissection experience, and finally, the analysis of data retrieved during the dissection step was a complete method for training manual dexterity and hand-eye coordination and to improve the general knowledge of surgical approaches. CONCLUSIONS: The present model results are found to be effective, providing a valuable representation of the surgical anatomy as well as a 3D visual feedback, thus improving study, design, and execution in a variety of approaches. Such a system can also be developed as a preoperative planning tool that will allow the neurosurgeon to practice and manipulate 3D representations of the critical anatomic landmarks involved in the endoscopic endonasal approaches to the skull base.

The use of a three-dimensional novel computer-based model for analysis of the endonasal endoscopic approach to the midline skull base.

OBJECTIVES: To apply a three-dimensional geometric model to various endoscopic endonasal approaches to analyze the bony anatomy of this area, quantify preoperatively bone removal, and optimize surgical planning. METHODS: Investigators dissected 18 human cadaveric heads at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain). Before and after each dissection, a computed tomography (CT) scan was performed to create a three-dimensional geometric model of the approach performed in the dissection room. The model protocol was designed as follows: (i) a preliminary exploration of each specimen using the preoperative CT scan, (ii) creation of a computer-generated three-dimensional virtual model of the approach, (iii) cadaveric anatomic dissection, and (iv) development of a CT-based model of the approach as a result of the superimposition of predissection and postdissection digital imaging and communications in medicine (DICOM) images of specimens. RESULTS: This method employing preliminary virtual exploration of each specimen, the creation of a three-dimensional virtual model of the approach, and the overlapping of the predissection and postdissection three-dimensional models was useful to define the exact boundaries of the endoscopic endonasal craniectomy. CONCLUSIONS: Aside from laboratory anatomic dissection itself, this model is very effective in providing a depiction of bony landmarks and visual feedback of the amount of bone removed, improving the design of the craniectomy in the endoscopic endonasal midline skull base approach.

Preliminary experience with a new three-dimensional computer-based model for the study and the analysis of skull base approaches.

PURPOSE: The goal of the present study was to develop a three-dimensional (3D) geometrical model based on pre- and post-dissection Digital Imaging and Communication in Medicine (DICOM) images of both transcranial and endonasal skull base approaches. Such model was structured for either teaching surgical anatomy and to evaluate the amount of bone removal over the skull base surface through a 3D digital perspective. METHODS: Twenty-five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy (LSNA) of the University of Barcelona (Spain) between 2007 and 2009. Before and after each dissection, a computed tomography-scan (CT-scan) was obtained in order to create a 3D geometrical model of the same approach performed in the dissection laboratory. The model protocol was designed as follows: (1) preoperative CT-scan of the specimens; (2) creation of a computer-generated 3D model of the specimen using specific imaging software for visualization and manipulation of biomedical data; (3) dissection of the specimens; (4) development of a 3D CT-based model of the approach as a result of the overlapping of the DICOM data of the specimens before and after the dissection. RESULTS: The fusion of the pre- and post-dissection 3D models allowed evaluation of the amount of bone removal over the skull base surface. CONCLUSIONS: Measurements of the bony landmarks as well as the visual feedback of the drilled bone over the skull base provided by our 3D model gives the opportunity to improve the tailoring of each approach to the different skull base areas.

Endoscopic endonasal transclival approach and retrosigmoid approach to the clival and petroclival regions.

OBJECTIVE: The removal of clival lesions, mainly those located intradurally and with a limited lateral extension, may be challenging because of the lack of a surgical corridor that would allow exposure of the entire lesion surface. In this anatomic study, we explored the clival/petroclival area and the cerebellopontine angle via both the endonasal and retrosigmoid endoscopic routes, aiming to describe the respective degree of exposure and visual limitations. METHODS: Twelve fresh cadaver heads were positioned to simulate a semisitting position, thus enabling the use of both endonasal and retrosigmoid routes, which were explored using a 4-mm rigid endoscope as the sole visualizing tool. RESULTS: The comparison of the 2 endoscopic surgical views (endonasal and retrosigmoid) allowed us to define 3 subregions over the clival area (cranial, middle, and caudal levels) when explored via the endonasal route. The definition of these subregions was based on the identification of some anatomic landmarks (the internal carotid artery from the lacerum to the intradural segment, the abducens nerve, and the hypoglossal canal) that limit the bone opening via the endonasal route and the natural well-established corridors via the retrosigmoid route. CONCLUSION: Different endoscopic surgical corridors can be delineated with the endonasal transclival and retrosigmoid approaches to the clival/petroclival area. Some relevant neurovascular structures may limit the extension of the approach and the view via both routes. The combination of the 2 approaches may improve the visualization in this challenging area.