Vestibular neuronitis describes inflammation of the vestibular nerve. This is usually attributed to a viral infection.
Pathophysiology
The inner ear contains the bony labyrinth, a complex bony structure containing fluids (perilymph and endolymph). The inner ear is comprised of three parts:
- Semicircular canals
- Vestibule (middle section)
- Cochlea
The semicircular canals and otolith organs within the vestibule (the utricle and saccule) are responsible for detecting movement of the head. Together they form the vestibular system:
- The semicircular canals detect rotation of the head
- The otolith organs detect gravity and linear acceleration
The cochlea is responsible for hearing.
The vestibular nerve transmits signals from the vestibular system (the semicircular canals and vestibule) to the brain to help with balance. The cochlear nerve transmits signals from the cochlea to provide hearing. Together they form the vestibulocochlear nerve (the 8th cranial nerve).
Vestibular neuronitis refers to inflammation of the vestibular nerve. A viral infection may trigger this inflammation. It distorts the signals travelling from the vestibular system to the brain, confusing the signal required to sense movements of the head. This results in episodes of vertigo, where the brain thinks the head is moving when it is not.
Presentation
Typically, the history involves the acute onset of vertigo. In addition, there may be a history of a recent viral upper respiratory tract infection.
Symptoms are most severe for the first few days. Initially, vertigo may be constant, after which it is triggered or worsened by head movement. It is often associated with:
- Nausea and vomiting (may be severe)
- Balance problems
It is essential to differentiate between peripheral (inner ear) and central (brain) causes when a patient presents with vertigo. Any neurological signs or symptoms should make you consider a central cause of vertigo rather than vestibular neuronitis. This may require urgent management, particularly if posterior circulation infarction (stroke) is suspected.
TOM TIP: Tinnitus and hearing loss are not features of vestibular neuronitis, as the cochlea and cochlear nerve are not affected. If tinnitus and hearing loss are also present, consider labyrinthitis or Ménière’s disease as differential diagnoses. You can remember this with:
- Labyrinthitis – Loss of hearing
- Neuronitis – No loss of hearing
The Head Impulse Test
The head impulse test can be used to diagnose peripheral causes of vertigo, resulting from problems with the vestibular system (e.g., vestibular neuronitis or labyrinthitis).
The head impulse test involves the patient sitting upright and fixing their gaze on the examiner’s nose. The examiner holds the patient’s head and rapidly jerks it 10-20 degrees in one direction while the patient continues looking at the examiner’s nose. The head is slowly moved back to the centre before repeating in the opposite direction. Ensure they have no neck pain or pathology before performing the test.
A patient with a normally functioning vestibular system will keep their eyes fixed on the examiner’s nose.
In a patient with an abnormally functioning vestibular system (e.g., vestibular neuronitis or labyrinthitis), the eyes will saccade (rapidly move back and forth) as they eventually fix back on the examiner.
The head impulse test helps diagnose a peripheral cause of vertigo but will be normal if the patient has no current symptoms or a central cause of vertigo.
Management
The management here is adapted from the NICE clinical knowledge summaries (updated 2017). Always check local and national guidelines when treating patients.
Patients may need admission if they are becoming dehydrated due to severe nausea and vomiting.
For peripheral vertigo, short-term options for managing symptoms include:
- Prochlorperazine
- Antihistamines (e.g., cyclizine, cinnarizine and promethazine)
NICE advise that symptomatic treatment can be used for up to 3 days. More extended use may slow down the recovery.
NICE also recommend referral if the symptoms do not improve after 1 week or resolve after 6 weeks, as they may require further investigation or vestibular rehabilitation therapy (VRT).
Prognosis
Symptoms are most severe for the first few days, after which they gradually resolve over the following 2-6 weeks.
Benign paroxysmal positional vertigo (BPPV) may develop after vestibular neuronitis.
Last updated July 2021
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