Mastoid segment of facial nerve

The mastoid segment of facial nerve (F5) begins after the tympanic segment moves downwards, distal from the pyramidal eminence of the middle ear cavity, at the posterior genu of facial nerve (external geniculum of facial nerve). From here, the mastoid segment travels through the facial canal and up to the stylomastoid foramen.

This segment measures 8-14 mm in length and gives off three branches:

• The nerve to stapedius muscle

• the chorda tympani (containing parasympathetic fibers to sublingual and submandibular salivary glands and taste fibers from the anterior two-thirds of the tongue)

• The sensory branch, which joins the auricular branch of the vagus nerve. The sensory branch carries general somatic afferent fibers from the pinna and the external auditory meatus.