Extradural subtemporal transzygomatic approach to the clival and paraclival region with endoscopic assist

The authors describe the extradural subtemporal transzygomatic (ESTZ) approach and its variants to expose the clival and paraclival areas. A microanatomical study was conducted to quantify the clival and paraclival exposure and the maneuverability areas obtained by microscope and endoscope using the ESTZ approach. Section versus preservation of the third trigeminal branch (V3) and petrous apicectomy to obtain a wider clival exposure and a better internal carotid artery control are discussed. Eight cadaveric specimens were dissected to obtain morphometric measurements after performing the ESTZ approach and its variants. Anatomic areas exposed by the approaches were calculated using the ImageJ 1.37a software. The ESTZ approach performed with sectioning of V3 and petrous apicectomy allowed for a mean incremental exposed area of 1.8 cm2 (range, 1.24-2.43 cm2). The mean amount of additional anatomic areas visualized after the ESTZ approach with petrous apicectomy if compared with the ESTZ approach without petrous apicectomy was 24% (range, 14.4%-37.5%). The mean percentage increase of maneuverability area after petrous apicectomy was 69.9% (range, 43.8%-96.6%). The ESTZ approach is suitable when dealing with extradural tumors of the middle-upper clivus extending into the ipsilateral paraclival area. V3 section and petrous apicectomy increase the operability, the surgical exposure, and the maneuverability area and improve vascular control on the internal carotid artery. Application of endoscopy does not impact on the maneuverability area but enhances the visualization of blind corners; endoscopic surgical view without drilling the petrous apex is comparable to that obtained by the microscope after petrous apicectomy.