Cranial nerve · one in each half of the brain
Vestibulocochlear nerve (VIII)
Also called Cranial nerve VIII, CN VIII, Auditory nerve, Acoustic nerve, Eighth nerve
Two nerves in one: hearing from the snail-shaped cochlea and balance from the inner ear.
This nerve carries two senses from the inner ear. Its hearing part brings sound from the cochlea, a tiny snail-shaped tube. Its balance part brings news about which way your head is tilting, turning, and moving. Together they let you follow a conversation and walk in a straight line without falling over.
Where it is
It runs a short way from the inner ear, which is buried in hard bone deep inside the head, to the brainstem at the corner where the pons, medulla, and cerebellum meet.
What it does
Hearing
Tiny hair cells in the cochlea turn sound vibrations into signals, and the hearing part of the nerve carries them to the brainstem.
A pitch map
Different spots along the cochlea respond to different pitches, like the keys of a rolled-up piano, and the nerve keeps them in order.
Balance
Three fluid-filled loops sense your head turning, and two small sacs sense gravity and straight-line movement, like an elevator starting or a car braking.
Steady eyes
Balance signals move your eyes opposite to your head, keeping the world steady when you walk or run.
Think of it as a two-lane road from the inner ear: one lane carries the soundtrack, the other carries a built-in bubble level and motion sensor.
Works with
- Inferior colliculusHearing signals pass through this midbrain relay, which helps work out where sounds are coming from.
- Medial geniculate nucleusSound then reaches this thalamus relay, the last stop before the cortex.
- Acoustic radiationThis fiber fan carries the sound signals on the final leg from the thalamus to the hearing cortex.
- Primary auditory cortexSounds finally arrive at the primary hearing cortex, where you become aware of them.
- Flocculonodular lobeBalance signals go straight to this oldest part of the cerebellum, which keeps you upright and your gaze steady.
- Abducens nerve (VI)Balance signals steer the eye-moving nerves, so your eyes automatically cancel out head movements.
When it goes wrong
How doctors check it
The doctor rubs fingers or whispers next to each ear, or uses a humming tuning fork. For balance, they may watch your eyes while quickly turning your head.
Acoustic neuroma
A slow-growing, non-cancerous lump on the nerve's outer covering can cause hearing loss in one ear, ringing, and unsteadiness. Hearing loss in just one ear is always worth getting checked.
Spinning dizziness
If the balance part becomes inflamed, often after a virus, the room can spin violently for days. Severe symptoms usually ease within a week, and most people are fully better within 2 to 3 months.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Shake your head gently from side to side while reading this and the words stay steady. That is your balance nerve at work, automatically moving your eyes the opposite way to your head.
- Motion sickness is thought to come from a mismatch: your inner ear feels movement while your eyes, fixed on a book or screen, say you are sitting still.
- Your tiny cochlea covers every pitch you can hear, from a deep rumble to a mosquito's whine.
By the numbers
Where the name comes from
Vestibulum is Latin for "entrance hall", the name for the central chamber of the inner ear. Cochlea comes from the Greek word for "snail", after the coiled shape of the hearing organ.
Learn it in a lesson
- Hearing and balanceFrom the inner ear to the cortex. A short guided lesson in 3D.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the vestibulocochlear nerve (VIII)?
Show the answer
Hearing. Tiny hair cells in the cochlea turn sound vibrations into signals, and the hearing part of the nerve carries them to the brainstem.
Hearing. Tiny hair cells in the cochlea turn sound vibrations into signals, and the hearing part of the nerve carries them to the brainstem.
The vestibulocochlear nerve (VIII) is part of which larger structure?
Show the answer
Cranial nerves. It belongs to the cranial nerves.
Cranial nerves. It belongs to the cranial nerves.
Which part fits this description? "Like a two-lane road from the inner ear: one lane carries the soundtrack, the other carries a built-in bubble level and motion sensor."
Show the answer
Vestibulocochlear nerve (VIII). It is the vestibulocochlear nerve (VIII). Two nerves in one: hearing from the snail-shaped cochlea and balance from the inner ear.
Vestibulocochlear nerve (VIII). It is the vestibulocochlear nerve (VIII). Two nerves in one: hearing from the snail-shaped cochlea and balance from the inner ear.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Cranial Nerve 8 (Vestibulocochlear), StatPearls, NCBI Bookshelf
- Neuroscience Online, Chapter 10: Vestibular System: Structure and Function, McGovern Medical School at UTHealth Houston
- Labyrinthitis, MedlinePlus, National Library of Medicine
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Explore the vestibulocochlear nerve (VIII) in 3D
Turn it around, zoom inside and see how it connects to the rest of the brain, then test yourself with quick quizzes.
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