Corpus: Vestibulocochlear nerve

The paired vestibulocochlear nerve is the 8th cranial nerve. It conducts electrical impulses from the inner hair cells to the brainstem along the auditory pathway and from the sensory cells of the vestibular organ to the central vestibular nuclei. It also carries efferent fibers that modulate the outer hair cells.

The vestibulocochlear nerve is composed of two parts: the cochlear root (radix cochlearis) and the vestibular root (radix vestibularis).

The cochlear root begins as a special somatosensory cranial nerve at the cell bodies (perikarya) in the cochlear ganglion of the inner ear. The vestibular root originates in the vestibular ganglion, which consists of a superior and an inferior part.

Both roots are enclosed in a common connective tissue sheath and run through the internal acoustic meatus to the internal acoustic pore, where they enter the posterior cranial fossa. The nerve runs along the lower edge of the pons, immediately caudolateral to the facial nerve, into the brainstem. Here, the vestibular and cochlear fibers separate again and proceed to their respective cranial nerve nuclei.

• Utriculoampullary nerve
• Utricular nerve
• Anterior ampullary nerve
• Lateral ampullary nerve
• Posterior ampullary nerve
• Saccular nerve

The fibers of the vestibulocochlear nerve terminate in nuclei and are transmitted from there to different regions:

• Superior, medial, and inferior vestibular nuclei: to the vestibular organ
• Lateral vestibular nuclei: carry most of the fibers from the Purkinje cells of the cerebellum
• Anterior and posterior cochlear nuclei: to the auditory apparatus

Failure of the vestibulocochlear nerve leads to deafness and balance disorders. The functionality of the nerve is measured using auditory brainstem response (ABR) testing.