Vestibulocochlear Nerve: Schema Anatomy
1. Geniculum of facial nerve (site of geniculate ganglion)
2. Greater petrosal nerve
3. Cochlear (spiral) ganglion
4. Vestibulocochlear nerve (CN VIII)
5. Chorda tympani nerve
6. Facial canal and nerve
7. Vestibular ganglion
Comment: The facial and vestibulocochlear nerves traverse the internal acoustic meatus together. The facial nerve makes a sharp bend at the level of the geniculate (sensory) ganglion of the facial nerve before descending and exiting the skull through the stylomastoid foramen. It sends preganglionic parasympathetic fibers to the pterygopalatine ganglion (via the greater petrosal nerve) and to the submandibular ganglion (via the chorda tympani nerve).
The vestibulocochlear nerve carries special sensory fibers from the cochlea via the cochlear nerve (auditory) and from the vestibular apparatus via the vestibular nerve (balance). These 2 branches join and leave the inner ear via the internal acoustic meatus to pass to the brain.
Clinical: Vertigo is a symptom involving the peripheral vestibular system or its central nervous system connections and is characterized by the illusion or perception of motion. Hearing loss can be sensorineural, suggesting a disorder of the inner ear or cochlear division of CN VIII. Conductive hearing loss suggests a disorder of the external or middle ear (tympanic membrane and/or middle ear ossicles).