8th Cranial Nerve – Vestibulocochlear nerve Lesions

Definition:

The vestibulocochlear nerve, cranial nerve VIII, is responsible for sound and equilibrium. A lesion affecting this nerve is a pathological process with the potential to negatively affect its function.

Causes:

There are numerous possible mechanisms by which the vestibulocochlear nerve can be injured. The resulting signs and symptoms will vary depending on whether the vestibular, the cochlear, or both portions of the nerve are affected. Below is a list of possible causes:

  • Acoustic neuroma
  • Otitis media
  • Labyrinthitis
  • Tumors, especially those within the cerebello-pontine angle
  • Fractures to the petrous portion of the temporal bone
  • Osteosclerosis
  • Meniere’s disease
  • Trauma

Examination:

The patient should be assessed for the following signs and symptoms:

  • Hearing loss
  • Vertigo
  • Disequilibrium
  • Nystagmus
  • Motion-sickness

It is important to bear in mind that disequilibrium may also be caused by cerebellar dysfunction; it is therefore the examiners role to discern between the two.

Hearing loss can be divided into sensory-neural and conductive, and discriminated by using the Weber and Rinne tests.