3D Exoscope System in Neurosurgery-Comparison of a Standard Operating Microscope With a New 3D Exoscope in the Cadaver Lab.

BACKGROUND: For decades, the operating microscope has been the "gold standard" visualization device in neurosurgery. The development of endoscopy revolutionized different surgical disciplines, whereas in neurosurgery, the endoscope is commonly used as an additional device more than as single visualization tool. Invention of a 3D exoscope system opens new possibilities in visualization and ergonomics in neurosurgery. OBJECTIVE: To assess the prototype of a 3D exoscope (3D exoscope, year of manufacture 2015, FA Aesculap, Tüttlingen, Germany) as neurosurgical visualization device in comparison to a standard operating microscope. METHODS: A pterional approach was performed in 3 ETOH-fixed specimens (6 sides). A standard operating microscope was compared to a 3D exoscope prototype. Dimensions like visual field, magnification, illumination, ergonomics, depth effect, and 3D impression were compared. RESULTS: In all approaches, the structures of interest could be clearly visualized with both devices. Magnification showed similar results. The exoscope had more magnification potential, whereas the visual quality got worse in higher magnification levels. The illumination showed better results in the microscope. Surgeons felt more comfortable with the 3D exoscope, concerning ergonomic considerations. Depth effect and 3D impression showed similar results. None of the surgeons felt uncomfortable using the exoscope. CONCLUSION: The operating microscope is the gold standard visualization tool in neurosurgery because of its illumination, stereoscopy, and magnification. Nevertheless, it causes ergonomic problems. The prototype of a 3D exoscope showed comparable features in visual field, stereoscopic impression, and magnification, with a clear benefit concerning the ergonomic possibilities.

Evaluation of a 3-dimensional voxel-based neuronavigation system with perspective image rendering for keyhole approaches to the skull base: an anatomical study.

BACKGROUND: Keeping track of the endoscope tip in 3 planes (axial, coronal, and sagittal) while performing skull base surgeries can be difficult because the surgeon is focused most on the live video images of the endoscope. For that reason, it was the aim of this anatomical cadaver study to evaluate the usefulness of a voxel-based neuronavigation system with 3-dimensional (3D) perspective image rendering for endoscopic procedures through keyhole approaches to the skull base. METHODS: On 5 whole-body fixed cadavers, frontolateral and retrosigmoid approaches were performed bilaterally using a neuronavigation system with 3D perspective image rendering (Cbyon, Med-Surgical Services Inc., Sunnyvale, California). Target points defined on the selected target structures were approached with the navigated ∅ 4-mm 0° endoscope (Storz, Tuttlingen, Germany). Using an Endocameleon 4-mm rigid endoscope capable of changing its angle of view while remaining stationary, the surgical field was checked for injuries before and after insertion of the navigated 0° endoscope. RESULTS: The median neuronavigation registration error was 0.95 mm (range 0.6 to 1.2 mm). Evaluation showed that 100% of the defined targets were reached and visualized. Neither a target structure nor neurovascular structures or surrounding brain tissue were injured by the navigated 0° endoscope. CONCLUSIONS: A neuronavigation system with 3D voxel-based perspective image rendering could potentially improve safety during complex skull base surgeries, and possibly also help to improve surgical results. Such a system, however, cannot replace a neurosurgeon's experience nor surgical skill or anatomical knowledge. It is an excellent teaching tool for young neurosurgeons, but it also has some limitations. Therefore, clinical studies will be necessary to further evaluate the benefits of this type of neuronavigation system in a clinical setting.

Actual state of EndActive ventricular endoscopy.

PURPOSE: We assessed usability and applicability of a rigid, multidirectional steerable videoendoscope (EndActive, Karl Storz GmbH, Tuttlingen, Germany) for endoscopic third ventriculostomy and compared our experience with reports about other multidirectional endoscopes. METHODS: The prototype is a 4-mm-diameter rigid videoendoscope with an integrated image sensor comprising an embedded light source, offering a free viewing direction in a range of 160° while the tip itself does not move. In five specimens (ten sides), we introduced the endoscope via precoronal burr holes through the lateral ventricle and foramen of Monro into the third ventricle. The endoscope's tip was positioned at the level of the mamillary bodies and the previously defined anatomical target structures; anteriorly, the optic chiasm, anterior commissure, infundibulum, tuber cinereum and posteriorly, the entrance to the mesencephalic aqueduct and posterior commissure were inspected. RESULTS: A single insertion of the videoendoscope was sufficient to explore with the multiplanar viewing mechanism the entire third ventricle. The prototype videoendoscope may be held like a microsurgical instrument in one hand. It is feasible to control movements precisely due to the reduced weight and ergonomic shape of the device. CONCLUSIONS: The prototype EndActive has the potential to fit in the current concept of ETV and enrich the setting adding working economy and viewing variability.

Developments in neuroendoscopy: trial of a miniature rigid endoscope with a multidirectional steerable tip camera in the anatomical lab.

The aim of this study is to assess field of view, usability and applicability of a rigid, multidirectional steerable video endoscope (EndActive) in various intracranial regions relevant to neurosurgical practice. In four cadaveric specimens, frontolateral, pterional, transnasal (to sella and clivus), interhemispheric (transcallosal and retrocallosal) and retrosigmoid approaches as well as precoronal burr holes for ventriculoscopy were performed. Anatomical target structures were defined in each region. We assessed field of view as well as optical and ergonomic features of the prototype. The EndActive is a 4-mm-diameter rigid video (endo)scope with an integral image sensor comprising an embedded light source. The viewing direction in a range of 160° can either be controlled by the computer keyboard or a four-way joystick mounted to the handle section of the endoscope. The endoscopic imaging system allows the operator to simultaneously see both a 160° wide-angle view of the site and an inset of a specific region of interest. The surgeon can hold the device like a microsurgical instrument in one hand and control movements precisely due to its reduced weight and ergonomic shape. The multiplanar variable-view rigid endoscope proved to be useful for following anatomical structures (cranial nerves I-XII). The device is effective in narrow working spaces where movements jeopardize the delicate surrounding structures. The multiplanar variable viewing mechanism in a compact device offers advantages in terms of safety and ergonomics. Improving the usability will probably optimize the applicability of endoscopic techniques in neurosurgery.

Optical requirements on magnification systems for intracranial video microsurgery.

INTRODUCTION: The basic idea of video-microsurgery is the improvement of ergonomic conditions in microsurgical procedures by replacing the bulky operating microscope with a compact videosystem. OBJECTIVE: To specify optical requirements on a videosystem for microsurgical intracranial procedures in neurosurgery. METHODS: During 27 microsurgical intracranial procedures (12 cerebellopontine angle and 15 supratentorial) zoom factor, focus distance and illumination parameters of the operating microscope were continuously recorded. Ergonomic aspects were documented as well. RESULTS: The zoom factor ranged from 1.7 to 13.5 in CPA procedures and from 1.4 to 13.4 in supratentorial procedures. The focus distance ranged from 180 mm to 367 mm in CPA procedures and from 188 mm-472 mm in supratentorial procedures. CONCLUSION: From an optical point of view current operating microscopes meet the requirements of intracranial microneurosurgery. However, ergonomically further developments are highly desirable. Video microsurgery is a promising field and could hold a solution to this problem.