Endoscopic Assistance in the Epidural Subtemporal Approach and Kawase Approach: Anatomic Study

BACKGROUND: Few reports exist in the literature about the use of endoscope assistance in the identification of structures in the posterior fossa. OBJECTIVE: To asses the advantage of endoscopic assistance in the epidural subtemporal and Kawase approaches by studying anatomic exposure and surgical freedom in the posterior cranial fossa. METHODS: Twelve epidural subtemporal approaches were performed on 6 adult cadaveric heads. On the same specimens, 6 endoscope-assisted subtemporal approaches and 6 Kawase approaches were then performed. At the end of each Kawase approach, endoscope assistance was used. The microsurgical observations were performed with a surgical microscope with magnification ranging from 4 x to 40 x. Endoscopic observations were made with a 0 degrees,4-mm rod-lens endoscope. Anatomic exposure and surgical freedom were analyzed. RESULTS: Endoscopic assistance during the epidural subtemporal approach increased the anatomic exposure 3 mm superiorly, 20 mm inferiorly, and 10 mm medially from the trigeminal nerve. Surgical freedom was limited in the temporal lobe, the petrous apex, and the trigeminal nerve. The amount of increased anatomic exposure obtained with endoscopic assistance during the Kawase approach was 26 mm inferiorly and medially from the trigeminal nerve. Surgical freedom was limited by the brainstem and the depth of the posterior cranial fossa. CONCLUSION: The endoscope-assisted subtemporal approach can be useful in visualizing tumor in the posterior fossa. It can help the surgeon in planning further surgical steps through consideration of the size, extension, and adherence of the tumor to surrounding structures. The endoscope-assisted Kawase approach permits maximum anatomic exposure of the posterior cranial fossa, although the deepest neurovascular structures could be better addressed with more direct approaches.