Broadening horizons of neuroendoscopy with a variable-view rigid endoscope: An anatomical study

Aim: To test the versatility and usefulness of a prototype rigid endoscope with a continuously variable-view-angle tip (Endochamaeleon, Karl Storz, Tuttlingen, Germany) with regard to field of vision and applicability for endoscopic assisted neurosurgery. Methods: In five formaldehyde fixed specimens frontolateral and retrosigmoid approaches were prepared on both sides and five target positions of the endoscopes tip were defined. A rigid 4 mm endoscope, which offers in one plane a viewing range of approximately -10° to +120° by turning a proximal knob coupled to fine distal optomechanics was compared to 0°, 45°, and 70° rigid endoscopes. The visualizable neuroanatomical structures were assessed for each position, endoscope angle, and plane of view as well as the over-all visibility of neuroanatomical structures and the time factor. Results: 1905 recorded images of 1800 different views were analyzed. The EC offers a variable angle of view in one plane without need to change the endoscope position. This feature is well suited for inspection of functionally delicate areas at the skull base. The maximum number of visible structures for each position was only seen with the EC. Endoscopic exploration was significantly less time consuming with the EC than with the other endoscopes. Conclusion: The EC provided superior usability and visualization potential compared to standard rigid endoscopes with fixed angulation. It combines the ergonomic and safety advantage of not having to insert endoscopes with different angles with the opportunity to "scan" the surgical field with a variable angle of 0°-120° within one plane of view.