Superior branch of vestibular nerve

The superior branch of vestibular nerve provides sensory innervation to specific components of the membranous labyrinth, including the (ampullas of) lateral and anterior semicircular canals, as well as the (macula of) utricle and superior part of the (macula of) saccule.

Please note that the sensory information from the remaining parts of the membranous labyrinth, such as, the (ampulla of) posterior semicircular canal and inferior part of the (macula of) saccule, is transmitted by a separate group of neuronal afferents that run in the inferior branch of vestibular nerve.

When comparing the two branches of vestibular nerve, the superior branch is significantly longer and passes through a single and narrower bony canal containing lots of bony spicules and interspersed reticular bone. This is in contrast to the inferior branch of vestibular nerve which runs in two distinct bony canals, as two separate portions of the same inferior nerve, with each part having its independent blood supply. These anatomical differences make superior branch of vestibular nerve more prone to entrapment and damage by ischemia, when it swells up in a viral infection. In some instances, the superior branch develops transnerval anastomosis with the facial nerve, which could facilitate the spread of vestibular neuritis to the facial nerve.