Modified Partial Labyrinthectomy Petrous Apicectomy Approach: An Microanatomic Study

Objective Known as 'inaccessible area', the petroclival region is deep-located and difficult to expose because of that is surrounded by many important neurovascular stractures. Partial labyrinthectomy petrous apicectomy approach is a relatively new skull-base approach to the petroclival region. However, the limitation of this approach is the traumatization caused by large-sized craniotomy. The keyhole concept is applied to modify this approach for reducing surgery-related traumatization in this study.Methods Firstly, the distance between the osseous structures was measured on 10 dry skull (20 sides). Secondly, bilateral stepwise dissections were performed on 15 formalin-fixed and dye-injected cadaveric heads (30 sides) under × 7 to × 40 magnification. The petroclival region was exposed by the modified partial labyrinthectomy petrous apicectomy approach and the partial labyrinthectomy petrous apicectomy approach. The amount of dura exposed and the angles of exposure, provided by two approaches, were measured after the partial labyrinthectomy and the petrous apicectomy. The injury of the intrapetrous important structures were observed and estimated. The petroclival anatomic structures were observed. The results were analyzed statistically.Results Each step of operative procedure is accomplished within the 4cm × 3 cm craniotomy. On average, the distance between the petrous ridge and the groove of the greater petrosal nerve was 12.8mm, and that was 12.2mm between the petrous ridge and Donaldson's line. On average, there were an increase of 14.2mm in horizontal exposure and 12.5mm in perpendicular exposure after the partial labyrinthectomy and the petrous...