Neuritis Vestibular

01Pathophysiology

Vestibular neuritis results from inflammation of the vestibular nerve, predominantly involving the superior division of the vestibular nerve (which innervates the superior and lateral semicircular canals and the utricle). The most widely accepted theory attributes the inflammation to reactivation of herpes simplex virus type 1 (HSV-1) latent in the vestibular ganglion (Scarpa's ganglion), analogous to how HSV reactivates in the geniculate ganglion in Bell's palsy. Histopathologic studies of temporal bones from patients who had vestibular neuritis have demonstrated viral particles and demyelination confined to the vestibular nerve.

The inflammation causes a sudden unilateral loss of vestibular afferent input to the brainstem vestibular nuclei. Under normal conditions, both vestibular nuclei maintain a balanced tonic firing rate. When one side is acutely silenced, the intact contralateral side generates an unopposed tonic signal. The brainstem interprets this asymmetry as continuous head rotation toward the healthy side, which is why the patient perceives relentless rotational vertigo.

This vestibular tone imbalance also explains the nystagmus pattern. The slow phase drifts toward the lesion side (because vestibular output from that side is reduced), and the fast corrective phase (which defines the direction of nystagmus) beats away from the affected ear. Because the superior vestibular nerve also carries some otolithic and torsional canal information, the nystagmus has both a horizontal and a torsional component.

The head impulse test (HIT) is positive because the damaged vestibular nerve cannot generate the brisk vestibulo-ocular reflex (VOR) needed to stabilize gaze during rapid head turns toward the affected side. The eyes lag behind, producing a visible corrective catch-up saccade back to the target. This is a critical peripheral localizing sign.

Importantly, the cochlear nerve is not involved in vestibular neuritis. The cochlear nerve and the inferior vestibular nerve run through a separate bony channel (the foramen singulare), which provides some anatomic protection. This is why hearing is preserved. If hearing loss accompanies the vertigo, the diagnosis shifts to labyrinthitis, not vestibular neuritis.

Over days to weeks, the brainstem undergoes central vestibular compensation: the intact side recalibrates its tonic output, and cerebellar circuits rebalance the vestibular nuclei. This is why symptoms gradually improve, and it is also why early mobilization and vestibular rehabilitation are essential for recovery.

02Classification and Clinical Manifestation

Vestibular neuritis is classified by which division of the vestibular nerve is affected, and this determines which semicircular canals and otolith organs show dysfunction on testing.

The natural course of vestibular neuritis follows a recognizable timeline:

03Diagnostic Workup

Walkthrough of the workup:

The diagnosis of vestibular neuritis is fundamentally clinical. In the exam setting, you are expected to recognize the pattern at the bedside, not by ordering advanced imaging.

The HINTS exam is the single most important bedside tool for a patient presenting with acute continuous vertigo. It stands for Head Impulse, Nystagmus, and Test of Skew. A "peripheral" or "benign" HINTS pattern consists of: (1) a positive head impulse test (corrective saccade present, indicating a peripheral VOR deficit), (2) unidirectional nystagmus that obeys Alexander's law (increases when gazing in the direction of the fast phase), and (3) no skew deviation on alternating cover test. If all three features point to a peripheral lesion, the sensitivity for identifying a peripheral cause exceeds 95%, and this pattern has been shown to outperform early MRI in detecting posterior fossa stroke.

A dangerous or "central" HINTS pattern would include any one of: a negative (normal) head impulse test in a patient with acute vertigo (meaning the VOR is intact despite the patient's severe symptoms, suggesting a central lesion bypassing the vestibular nerve), direction-changing nystagmus, or the presence of skew deviation. Any one of these central signs warrants urgent MRI with DWI sequences to rule out cerebellar or brainstem stroke, particularly posterior inferior cerebellar artery (PICA) territory infarction.

Caloric testing via videonystagmography (VNG) is the confirmatory test for documenting unilateral vestibular hypofunction. Warm and cool water (or air) are irrigated into each ear canal sequentially, and the resulting nystagmus is measured. A canal paresis greater than 20 to 25% on the affected side confirms the diagnosis. This test is typically ordered in the outpatient setting once the acute phase has passed, not in the emergency department.

Audiometry is ordered not to confirm vestibular neuritis, but to exclude labyrinthitis. If the audiogram shows sensorineural hearing loss on the affected side, the diagnosis becomes labyrinthitis. Normal hearing is a defining feature of vestibular neuritis.

MRI of the brain is not required to diagnose vestibular neuritis, but it is the study you order when you are worried about a central cause. Its primary role is to exclude stroke. Note that early DWI can miss small cerebellar infarcts in the first 24 to 48 hours (up to 20% false-negative rate), which is why the HINTS exam is considered superior to MRI in the hyperacute period for distinguishing peripheral from central vertigo.

04Management and Treatment

Acute stabilization (first 72 hours):

In the acute phase, the patient is often incapacitated with vertigo and vomiting. The immediate priority is symptomatic relief. Vestibular suppressants such as meclizine (an antihistamine), dimenhydrinate, or low-dose benzodiazepines (diazepam) reduce the tonic firing asymmetry perceived by the brainstem. Antiemetics are given concurrently.

If the patient presents within 72 hours of onset, a short course of corticosteroids should be considered. The most cited regimen is methylprednisolone 100 mg/day, tapered by 20 mg every 3 days over approximately 3 weeks. The rationale is to reduce inflammation and edema of the vestibular nerve within the bony canal, potentially preserving vestibular function. Evidence from the Strupp et al. (2004) trial showed improved caloric recovery at 12 months in steroid-treated patients. Antivirals (such as valacyclovir) have not been shown to add benefit beyond steroids alone and are not recommended.

The single most critical management point tested on exams: vestibular suppressants must be stopped after 48 to 72 hours. Continuing them beyond this window impairs the brainstem's ability to undergo central vestibular compensation, because the drugs dampen the very neural signals that drive the recalibration process. This is a commonly tested concept.

Long-term management:

The cornerstone of long-term recovery is vestibular rehabilitation therapy (VRT). This consists of graded exercises designed to promote central compensation:

• Gaze stabilization exercises: the patient fixates on a stationary target while moving the head back and forth, retraining the VOR.

• Habituation exercises: repeated exposure to movements that provoke dizziness, gradually desensitizing the vestibular system.

• Balance and postural training: progressive exercises on unstable surfaces to retrain proprioceptive and visual-vestibular integration.

VRT should begin as soon as the patient can tolerate head movement (typically within 2 to 5 days of onset). Multiple randomized trials have demonstrated that early VRT significantly accelerates recovery and reduces the risk of chronic dizziness.

Contraindications and considerations:

Corticosteroids should be used cautiously in patients with uncontrolled diabetes, active peptic ulcer disease, or immunosuppression. In these populations, the risk-benefit ratio must be weighed individually. Benzodiazepines should be avoided in the elderly or in patients at risk for falls, as sedation compounds the existing postural instability.

A subset of patients (approximately 10 to 15%) develop benign paroxysmal positional vertigo (BPPV) as a secondary complication weeks after the initial neuritis, likely due to otoconia displacement from the damaged utricle. If the patient returns with brief positional vertigo triggered by rolling over in bed, the Dix-Hallpike test should be performed, and treatment is the Epley maneuver, not a repeat course of steroids.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on vestibular neuritis questions is by confusing a peripheral pattern with a central pattern on the HINTS exam. The critical trap is this: a normal (negative) head impulse test in a patient with acute vertigo is not reassuring. It is actually an alarming sign. In vestibular neuritis, the VOR is broken on the affected side, so the HIT should be abnormal (positive). If the HIT is normal, the vestibular nerve and peripheral apparatus are functioning, which means the vertigo is originating centrally, and you must suspect stroke. Exam writers exploit this by presenting a patient with acute vertigo, nausea, and a "normal" HIT, hoping students will incorrectly choose vestibular neuritis because the symptoms sound peripheral.

The second common trap involves prolonged use of vestibular suppressants. When a vignette describes a patient with vestibular neuritis who is "not improving after two weeks," the answer is almost never to add stronger medication. Instead, the correct next step is to discontinue suppressants and initiate vestibular rehabilitation. The suppressants themselves are the obstacle to recovery.

Third, students often confuse vestibular neuritis with labyrinthitis. The distinguishing feature is straightforward but easily overlooked: hearing loss means labyrinthitis, no hearing loss means vestibular neuritis. If the stem includes any mention of reduced hearing, tinnitus, or abnormal audiometry on the affected side, do not select vestibular neuritis.

Finally, remember that MRI can be falsely negative in the first 24 to 48 hours after a posterior fossa stroke. A normal MRI in the hyperacute setting does not exclude stroke. The HINTS exam, when performed by a trained examiner, has been shown to be more sensitive than early DWI-MRI for detecting posterior circulation infarcts. If the HINTS pattern is central, pursue stroke workup regardless of initial MRI results.

The core competency being tested is the ability to differentiate peripheral from central vertigo at the bedside using the HINTS exam, to recognize the natural history of vestibular neuritis, and to understand why early vestibular rehabilitation and timely discontinuation of suppressants are the most important management decisions.