Facial nerve malformations from the prepontine cistern to the temporal bone

Congenital malformation of the inner ear may be associated with anomalous course of the facial nerve and several descriptions have been made of the nerve course into the temporal bone in presence of inner ear malformations. The tympanic, posterior genu and mastoid tracts have been widely investigated as directly related to surgery for cochlear implantation and thus amenable to iatrogenic damage. The present pictorial review aims to describe the possible anomalous course of the cisternal, canalicular and labyrinthine segments of the facial nerve particularly when associated to inner ear and internal auditory canal malformations as identified on imaging of the temporal bones. Analysis of this less surgically related segments of the nerve may shed some light over our understanding of inner ear and temporal bone embryology and congenital pathology.