Extended Middle Cranial Fossa Approach

Introduction

Gaining access to the cerebellopontine angle (CPA) and prepontine cistern presents a formidable challenge. Approaches designed to expose infraclinoid basilar tip aneurysms, petroclival meningiomas, chondromas, chondrosarcomas, and chordomas involving the petrous apex and clivus must preserve vital neighboring neurovascular structures. ^, Risks encountered in the prepontine cistern during the management of aneurysms of the posterior circulation were best described by Drake in 1961: “the upper clival region is to be considered no-man’s land.” Several conventional neurosurgical approaches to this region have been described, including the subtemporal, trans-sylvian and a combination approach incorporating both techniques. Modern skull base approaches, including the middle cranial fossa and the middle fossa transpetrous or extended middle fossa (EMF), have been instrumental in removing the petrous barrier, minimizing temporal lobe retraction, and improving the line of sight for the neurosurgeon.

The middle fossa approach was first described in the literature in 1904. The seminal work of House in 1961 introduced a refinement of this approach to the internal auditory canal (IAC), CPA, and prepontine cisterns. By extending the traditional middle fossa dissection anteriorly to the clivus, the EMF approach provides complete exposure of the IAC, prepontine cisterns and the mid- to upper clivus. Posteriorly, the approach allows access to tumors approaching but not entering the jugular foramen ( Box 48.1 ).

Technique

We administer preoperative antibiotics and continue them for 24 hours postoperatively. Intraoperative furosemide and mannitol are given facilitate eventual temporal lobe retraction. We administer dexamethasone intravenously during the procedure and continue this for 24 hours postoperatively. Long-acting muscle relaxants are avoided during surgery so as not to interfere with facial nerve monitoring.