The Vestibulocochlear Nerve (CN VIII)

Original Editor - Lucinda hampton

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Introduction[edit | edit source]

CN 8.png

The vestibulocochlear nerve, also known as cranial nerve eight (CN VIII), consists of the vestibular and cochlear nerves. It is located in the internal auditory meatus (internal auditory canal).

  • The vestibular nerve is primarily responsible for maintaining body balance and eye movements, while
  • The cochlear nerve is responsible for hearing.

CN VIII injuries are the result of pathological processes or injuries that commonly involve the cerebellopontine angle (CPA), the internal auditory canal (IAC), or the inner ear. In such cases, symptoms such as vertigo, nystagmus, tinnitus, and sensorineural hearing loss may occur[1]

Anatomy[edit | edit source]

Vestibulocochlear nerve.jpg

The vestibulocochlear is one of the 12 cranial nerves, it runs between the pons (the middle of the brainstem) and the medulla oblongata (the lower part of the brainstem).

  • The vestibular part of the nerve then travels from the inner ear in a group of nerve cells called the vestibular ganglion.
  • The cochlear part of the nerve travels from the cochlea in the inner ear in the spiral ganglion[2].

Image 2: Tractography showing vestibulocochlear nerve (a procedure to demonstrate the neural tracts using special techniques of MRI, and computer-based image analysis[3]).

Function[edit | edit source]

Vestibulocochlear Nerve.jpg

The function of the vestibulocochlear nerve is purely sensory. It has no motor function. It communicate sound and equilibrium information from the inner ear to the brain.

  • The cochlea, the part of the inner ear where the cochlear part of the nerve originates, detects soundwaves. These then travel from the spiral ganglion to the brain.
  • The vestibular apparatus, where the vestibular part of the nerve originates, detects changes in the head’s position based on gravity. Then the position of the head communicates information about balance to the brain[2].

Physiotherapy Implications[edit | edit source]

Balance-board-benefits.jpg

A problem with the sensory information being relayed to the brain via the vestibulocochlear nerve is termed a peripheral vestibular disorder. 

Conditions of the vestibulocochlear nerve can affect balance and hearing and may cause vertigo, vomiting, ringing in the ears, a false sense of motion, motion sickness, or even hearing loss.

Physiotherapists are commonly involved with the retraining of balance. See below links for more details.

References[edit | edit source]

  1. Bordoni B, Sugumar K, Daly DT. Neuroanatomy, cranial nerve 8 (vestibulocochlear). StatPearls [Internet]. 2020 Jan 12.Available from:https://www.ncbi.nlm.nih.gov/books/NBK537359/ (accessed5.2.2021)
  2. 2.0 2.1 Very well health CN VIII Available from:https://www.verywellhealth.com/vestibulocochlear-nerve-5095249 (last accessed 5.2.2021)
  3. Sensagent Tractography Available from:http://dictionary.sensagent.com/Tractography/en-en/ (accessed 5.2.2021)