Microsurgical Resection of Meningiomas Using a 4K Three-Dimensional Exoscope: A Descriptive Observational Study.

Background Prior to using the exoscope, we speculated that it represented an intermediate tool between a loupe and a microscope and had concerns about its visibility of deep, fine structures. Objective To evaluate the depths of meningioma for which the exoscope was suitable, and to clarify its disadvantages in meningioma resection. Methods Findings of consecutive meningioma surgeries using a 4K three-dimensional (3D) exoscope over a one-year period were evaluated for visibility of the surgical field, comfort of the surgeon's arm posture, the surgeon's head orientation, and perception of the image delay, accounting for the depth of the tumor. Results Seven meningiomas were resected using a 4K 3D exoscope (three superficial, three intermediate, and one deep). The exoscope allowed the surgeon to observe deeply located fine structures as clearly as with a conventional microscope and to operate more comfortably on meningiomas of all depths with arms flexed. On the contrary, the exoscope occasionally required the surgeon to operate with his head unnaturally turned to one side because of the immobility of its large monitor, despite the wide insertion availability of its camera from various directions to meningiomas located superficially or within the middle cranial fossa. No time delays between the surgeon's manipulations and the 3D images were perceived in all meningioma surgeries. Conclusions The 4K 3D exoscope was suitable for operations on all depths of meningiomas. The discrepancy between the surgeon's manipulation and gaze directions was its disadvantage. It is anticipated that further development of the 3D monitor will address this issue.