The Microanatomy To Petroclival Region Via Combined Keyhole Approach

Object Combine Subtemporal Transtentorial Keyhole Approach and Suboccipital-Retrosigmoid Keyhole Approach to observe the structure of petroclival region. Make an approach to deal with the enormous tumor and provide an anatomic basis to deal with the problem in this area.Methods Ten formalin-fixed adult cadaver heads of twenty sides were used for simulating the approach to observe the structure of petroclival region. Red emulsion was injected into the artery and blue emulsion into the vein. We fixed the cadaver head on headframe as the operation position. In Subtemporal Transtentorial Keyhole Approach the incision was made about 1.0cm long forward tragus and 4.0cm upper zygomatic arch. In Suboccipital-Retrosigmoid Keyhole Approach the vertical incision was made about 4.0cm long and 2.0cm long behind the mastoidale. Drilling the two holes about 2.0cm×2.5cm. After open the dura, pull away the lobe of brain and cut off the tentorium of cerebellum, use the"porch–scope"effect and change the point of view to observe petroclival region. Results In Subtemporal Transtentorial Keyhole Approach the mid skull base above the tentorium of cerebellum and cavernous sinus can be exposed clearly. After cut off part of the tentorium of cerebellum, CNⅢ,Ⅳ,Ⅴ,cisterna ambiens,PCoA,cupular part of BA,PCA and ante-lateral of midbrain can be exposed. But os petrosum face to posterior cranial fossa can't be seen because of the hinder of crista petrosa. The Suboccipital- Retrosigmoid Keyhole Approach can reach petroclival region from post-lateral side and can expose the lateral side of cerebellar hemisphere,petrous bone,CNⅤ～Ⅻ,lateral side of pons,petrosal vein,VA,AICA,PICA. Stripping part of the os petrosum can enlarge the exposure of CNⅤ.After cut open the edge of tentorium of cerebellum upward the CNⅣcan be exposure.Conclusion The combined keyhole approach provides too many sight ways to petroclival region. And the complicated tumors in this area can be cut off upper and down from tentorium of cerebellum. If the tumors extend to mid skull base,sella turcica or posterior cranial fossa this approach can be effective. But there are some risks in cutting off tentorium of cerebellum and stripping the superior thyroid tubercle of internal acoustic meatus. Meanwhile the keyhole approach needs refined instruments and rich experience operators.