Partial labyrinthectomy petrous apicectomy approach to the petroclival region: an anatomic and technical study

The petroclival region generally is thought to be an inaccessible area in the intracranial compartment. A number of ways of reaching this area during surgery have been described, including the presigmoid petrosal approach. The partial labyrinthectomy petrous apicectomy approach is a relatively new approach to this region and is a variant of the presigmoid petrosal approach. This study aims to demonstrate the technique and the microsurgical anatomy of the partial labyrinthectomy petrous apicectomy approach and to provide a quantitative study of its exposure to compare it with other common approaches to this region, particularly the presigmoid petrosal approach.

Bilateral stepwise dissections were performed on 15 formalin-fixed and dye-injected cadaveric heads (30 sides) under x3 to x40 magnification. A temporal craniotomy was performed after a complete mastoidectomy. A partial labyrinthectomy and petrous apicectomy were performed next. The amount of dura exposed was measured before and after the partial labyrinthectomy and the petrous apicectomy. By measuring the angles of exposure, the approach was examined to analyze how much increased access was gained.

This approach provided wide exposure to the petroclival region, the cerebellopontine angle, Meckel's cave, the cavernous sinus, and the prepontine region. On average, there was an increase of 10.8 mm in horizontal exposure as compared with the retrolabyrinthine approach. The average angle of vision achieved with the clival pit as the target was 58.9 degrees. In most of the specimens, an area from the IIIrd to the IXth cranial nerves was easily visible without any significant brain retraction. A high jugular bulb did not reduce the exposure.

The partial labyrinthectomy petrous apicectomy approach converts two narrow tunnels into a wide corridor. It increases the angle of exposure markedly, providing easy and excellent exposure of the otherwise difficult-to-access petroclival region, and it may also preserve hearing.