The vestibulocochlear nerve is the 8th cranial nerve, and gives us afferent information i.e. our balance and hearing. It leaves the skull through the same opening as the facial nerve (internal acoustic meatus) and arises from the pontomedullary junction lateral to the facial nerve. The nerve does not leave the skull, and its to divisions terminate in the inner ear.
The Vestibulocochlear nerve is also known as cranial nerve 8. It arises from the pontomedullary junction, lateral to the abducens (which lies just either side of the midline) and just lateral to the facial nerve. It leaves the cranial vault through the internal acoustic meatus (an opening in the petrous portion of the temporal bone), but the nerve never leaves the skull itself. The nerve divides into the vestibular and cochlear nerve.
The vestibular division arises from the vestibular system that lies in the inner ear. The vestibular ganglion is where the bipolar neurons are housed (in the outer part of the internal acoustic meatus), and it extends processes to five separate sensory organs. Three if these sensory inputs arise from the ampullae of the semi-circular canals. The hair cells in the cristae of these ampullae are displaced in response to rotational acceleration. The maculae of the saccule and utricle are the other two organs supplies by the vestibulocochlear nerve. They respond to linear acceleration, which causes the otoliths to be displaced. The cochlear division begins as the spiral ganglia, which collects information sent by the inner hair cell displacement in the Organ of Corti.
Vestibular schwannoma- This is a tumour of the schwann (myelin) cells of the vestibular division of the Vestibulocochlear nerve (cranial nerve 8). Symptoms include dizziness, vertigo, affected hearing (if the cochlear branch is also impinged), and if the tumour extrudes from the internal auditory meatus, also impinges the facial nerve, causing a Bell’s palsy.
Sensorineural deafness- This is deafness caused by an issue with the nervous system of the ear itself i.e. he inner ear (cochlear, hair cells etc). Causes include genetic conditions (Stickler syndrome, Waardenburg syndrome, Charcot-Marie-Tooth disease), congenital infections (rubella, cytomegalovirus, toxoplasmosis), Presbyacusis (normal age related hearing loss), or noise induced hearing loss (from listening to excessively loud music for a long time.
Labyrinthitis- Inflammation of the membranous labyrinth damages the vestibular and cochlear divisions of the vestibulocochlear nerve, resulting in tinnitus, nausea and vomiting, vertigo and nystagmus. Sensorineuronal hearing loss also occurs.
Ototoxic drugs- Ototoxic drugs include Gentamicin (an aminoglycoside antibiotic), heavy metals such as tin or mercury, as well as carbon monoxide.
Developmental precursor- Metencephalon (secondary brain vesicle)
Branches- Vestibular nerve, cochlear nerve
The vestibulocochlear nerve is the 8th cranial nerve, and gives us afferent information i.e. our balance and hearing. It arises from the pontomedullary junction lateral to the facial nerve.
1. Frank H.Netter MD: Atlas of Human Anatomy, 5th Edition, Elsevier Saunders, Chapter 1 Head and Neck
2. Chummy S.Sinnatamby: Last’s Anatomy Regional and Applied, 12th Edition, Churchill Livingstone Elsevier
3. Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, 2nd Edition, Churchill Livingstone Elsevier
4. Elliiot L.Manchell: Gray's Clinical Neuroanatomy: The Anatomic Basis for Clinical Neuroscience
5. The Definitive Neurological Surgery Board Review
By Shawn P. Moore, 2005
6. Human Neuroanatomy
By James R. Augustine, 2008