Vestibulocochlear Nerve (CN VIII)

Summary

The vestibulocochlear nerve, also known as cranial nerve 8 (CN VIII) or the eighth cranial nerve, is a nerve that transmits sensory information for our hearing and balance to the brain. As the sensory nerve that carries information about balance and orientation, the vestibulocochlear nerve controls the sensory or afferent component of the vestibulo-ocular reflex, used to stabilize our gaze in response to head movements. Anatomically, the nerve starts in our inner ears, and travels through the internal auditory meatus to enter the skull, from which it enters the pons at the cerebellopontine angle. Finally, the vestibulocochlear nerve is often affected by schwannomas, a tumor of Schwann cells which provide the myelin sheaths for peripheral nerves. These tumors are often located at the exit of the vestibulocochlear nerve from the brainstem, thereby impairing hearing and balance in patients.

Key Points

• Vestibulocochlear Nerve (Cranial Nerve VIII)
  • Nerve Type
    • Sensory
  • Function
    • Hearing
      • Receives inputs from cochlea in ear
      • Test using Rinne and Weber tests for conductive or sensorineural hearing loss
    • Balance (vestibular system)
      • Receives inputs from vestibular semicircular canals of ear
      • Test by asking patient to walk in straight line
  • Nerve entry/exit
    • Lateral pons at cerebellopontine angle 
      • Between cerebellum and lateral pons
    • Vestibular Nuclei at ponto-medullary junction
    • Cochlear nuclei in floor of 4th ventricle
  • Cranial Foramen
    • Internal auditory meatus
  • Reflexes
    • Vestibulo-ocular reflex (afferent sensory)
  • Other Information
    • Classically affected by schwannomas (acoustic neuromas)