The eighth cranial nerve, split into cochlear and vestibular divisions. The vestibular division carries balance and position signals from the inner ear to the brainstem.
Medical definition
The vestibular nerve is the vestibular branch of the vestibulocochlear nerve (cranial nerve VIII). It carries afferent signals from the three semicircular canals, the utricle, and the saccule to the vestibular nuclei in the brainstem. The nerve has superior and inferior divisions. The superior division innervates the lateral and anterior canals plus the utricle. The inferior division innervates the posterior canal and the saccule. The nerve fires continuously at a resting rate on both sides, and the brain reads balance by comparing the two sides. Any asymmetry — from disease, damage, or inflammation — is interpreted as movement.
Why it matters for vertigo
Vestibular neuritis is inflammation of the vestibular nerve, usually viral. It wipes out one side’s input suddenly, producing severe spinning vertigo, nausea, and imbalance that lasts days before the brain compensates. Acoustic neuroma (vestibular schwannoma) is a slow-growing tumour on this nerve — it causes progressive unilateral hearing loss and tinnitus before vertigo becomes prominent. The vestibular nerve is also the target of gentamicin injections used in Meniere disease — the drug selectively damages vestibular hair cells to reduce the attacks, at the cost of some vestibular function. Understanding which part of the nerve is affected guides diagnosis: superior division lesions produce a characteristic nystagmus pattern on vHIT.
Test.
Where I see this in clinic
In my OPD, the vestibular nerve is the structure I am thinking about every time a patient presents with sudden severe vertigo and no hearing loss.
Vestibular neuritis fits that picture perfectly, and the HINTS exam helps me decide whether the nerve or the brainstem is the cause.
On VNG, a unilateral caloric weakness points directly at reduced vestibular nerve function on that side.
The test assesses each individual nerve branch.
Canal-specific testing is possible with this method.
Video head impulse testing is a useful bedside tool.
Patients often ask if the nerve will recover. The answer is: partially, through central compensation, though some residual asymmetry often remains on formal testing even after symptoms resolve.
Related terms
Vestibular neuritis — inflammation of this nerve. Caloric test — measures nerve function by canal. Video head impulse test — assesses each nerve branch individually. HINTS exam — differentiates nerve from brainstem as the source.
Medical Disclaimer: This glossary entry is for educational purposes only and is not a substitute for in-person clinical assessment. Consult Dr. Prateek Porwal directly. WhatsApp: 7393062200.