The Intracranial Facial Nerve as Seen Through Different Surgical Windows: An Extensive Anatomosurgical Study

BACKGROUND:The facial nerve has a short intracranial course but crosses critical and frequently accessed surgical structures during cranial base surgery. When performing approaches to complex intracranial regions, it is essential to understand the nerveʼs conventional and topographic anatomy from different surgical perspectives as well as its relationship with surrounding structures. OBJECTIVE:To describe the entire intracranial course of the facial nerve as observed via different neurosurgical approaches and to provide an analytical evaluation of the degree of nerve exposure achieved with each approach. METHODS:Anterior petrosectomies (middle fossa, extended middle fossa), posterior petrosectomies (translabyrinthine, retrolabyrinthine, transcochlear), a retrosigmoid, a far lateral, and anterior transfacial (extended maxillectomy, mandibular swing) approaches were performed on 10 adult cadaveric heads (20 sides). The degree of facial nerve exposure achieved per segment for each approach was assessed and graded independently by 3 surgeons. RESULTS:The anterior petrosal approaches offered good visualization of the nerve in the cerebellopontine angle and intracanalicular portion superiorly, whereas the posterior petrosectomies provided more direct visualization without the need for cerebellar retraction. The far lateral approach exposed part of the posterior and the entire inferior quadrants, whereas the retrosigmoid approach exposed parts of the superior and inferior quadrants and the entire posterior quadrant. Anterior and anteroinferior exposure of the facial nerve was achieved via the transfacial approaches. CONCLUSION:The surgical route used must rely on the size, nature, and general location of the lesion, as well as on the capability of the particular approach to better expose the appropriate segment of the facial nerve. ABBREVIATIONS:AICA, anterior inferior communicating arteryCPA, cerebellopontine angleGG, geniculate ganglionIAC, internal auditory canalPICA, posterior inferior communicating artery