Labirintitis

01Pathophysiology

Labyrinthitis is an inflammatory process that involves the membranous labyrinth, the fluid-filled structure within the inner ear that houses both the vestibular organs (semicircular canals, utricle, saccule) and the cochlea. The critical distinction from vestibular neuritis is that labyrinthitis affects both the vestibular and cochlear compartments simultaneously, whereas vestibular neuritis is confined to the vestibular nerve and spares hearing.

In viral labyrinthitis, the most common form, a viral pathogen reaches the inner ear through hematogenous spread or by direct extension along neural pathways. The virus triggers an inflammatory cascade within the perilymphatic and endolymphatic spaces, causing edema, cellular infiltration, and potential damage to the hair cells of both the organ of Corti (cochlea) and the vestibular sensory epithelium. This dual involvement is why the patient simultaneously experiences vertigo and hearing loss.

The vestibular component produces a sudden asymmetry in tonic neural firing between the two vestibular nuclei. Under normal conditions, both vestibular apparatuses send balanced resting signals to the brainstem. When one side is acutely inflamed and hypofunction develops, the contralateral (healthy) side dominates. The brain interprets this imbalance as rotation, producing the sensation of vertigo. The nystagmus that results follows Alexander's law: the fast phase of nystagmus beats away from the lesioned side, and nystagmus intensity increases when the patient gazes in the direction of the fast phase.

The cochlear component leads to sensorineural hearing loss because the inflammatory process damages hair cells in the organ of Corti or disrupts the ionic environment of the endolymph (particularly the endocochlear potential maintained by the stria vascularis). Tinnitus results from aberrant spontaneous firing of damaged cochlear nerve fibers. Unlike the vestibular symptoms, which often recover substantially through central compensation, the hearing loss may be permanent depending on the degree of hair cell destruction.

Bacterial labyrinthitis follows a different route. It most often arises as a complication of otitis media (tympanogenic labyrinthitis), where bacteria or bacterial toxins penetrate through the round window membrane into the inner ear. It can also occur as a complication of bacterial meningitis (meningogenic labyrinthitis), where infection spreads from the subarachnoid space through the cochlear aqueduct. Bacterial labyrinthitis carries a far worse prognosis for hearing and can progress to labyrinthine ossification, particularly in post-meningitic cases, which is why urgent treatment and early cochlear implant evaluation matter in this subset.

The head impulse test is positive in labyrinthitis because the vestibulo-ocular reflex (VOR) on the affected side is impaired. When the examiner rapidly turns the patient's head toward the lesioned ear, the eyes cannot maintain fixation on the target, and a corrective catch-up saccade is observed. This finding localizes the lesion to the peripheral vestibular system and helps distinguish it from central causes where the VOR is typically preserved.

02Classification and Clinical Manifestation

By Etiology

By Clinical Phase

Distinguishing Feature from Vestibular Neuritis

03Diagnostic Workup

Labyrinthitis is fundamentally a clinical diagnosis supported by audiometry. The bedside evaluation is where the diagnosis begins. The examiner should first assess for spontaneous nystagmus. In labyrinthitis, the nystagmus is unidirectional, horizontal or horizontal-torsional, with the fast phase beating toward the healthy ear. It obeys Alexander's law and suppresses with visual fixation. These features are what classify it as a peripheral pattern and distinguish it from central causes.

The head impulse test (HIT) is performed next. The examiner asks the patient to fixate on the examiner's nose while the head is rapidly turned to each side. A corrective saccade when turning toward the affected ear confirms a peripheral vestibular deficit. A negative head impulse test in a patient with acute vertigo should raise concern for a central lesion, particularly posterior circulation stroke, and should prompt urgent imaging.

Audiometry is the single most important ancillary test. It is the study that distinguishes labyrinthitis from vestibular neuritis. The audiogram will show a unilateral sensorineural hearing loss on the affected side. The pattern may be low-frequency predominant, high-frequency predominant, or flat, depending on which portion of the cochlea is most affected. If the audiogram is completely normal, the diagnosis is vestibular neuritis, not labyrinthitis.

Tuning fork tests at the bedside serve as a rapid screen. The Weber test will lateralize to the unaffected ear (because the affected ear has sensorineural loss). The Rinne test will be positive bilaterally (air conduction greater than bone conduction on both sides), which confirms the loss is sensorineural rather than conductive.

MRI with gadolinium is not needed in every case but becomes the most accurate test when there is diagnostic uncertainty. It is ordered when the presentation is atypical: vertigo lasting beyond the expected timeframe, progressive hearing loss, neurologic signs, or failure to improve. MRI can show labyrinthine enhancement on post-contrast T1-weighted images in active inflammation and can exclude a vestibular schwannoma (which would present more insidiously with gradual unilateral hearing loss and may show a cerebellopontine angle mass). In post-meningitic labyrinthitis, MRI and CT temporal bone can detect early labyrinthine fibrosis or ossification, which is critical for timing of cochlear implantation.

Caloric testing via videonystagmography (VNG) provides objective documentation of vestibular hypofunction. Warm and cold water or air are irrigated into the ear canal, and the induced nystagmus is measured. A canal paresis greater than 20-25% on the affected side confirms unilateral vestibular loss. This test is useful for medicolegal documentation and for monitoring recovery but is not required for the initial clinical diagnosis.

04Management and Treatment

Acute Stabilization

The immediate priority in the acute phase is symptom relief. Patients with labyrinthitis are often incapacitated by vertigo, nausea, and vomiting. Vestibular suppressants work by dampening the asymmetric vestibular input reaching the brainstem. Diazepam is often preferred in the emergency setting because it acts on GABA receptors in the vestibular nuclei, providing both anxiolytic and direct vestibular suppression. Meclizine, an antihistamine with anticholinergic properties, is a reasonable alternative for outpatient management.

The key principle is that vestibular suppressants must be limited to the first 48-72 hours. Prolonged use impairs the brain's ability to undergo central compensation, the neuroplastic process by which the brainstem recalibrates to function with asymmetric vestibular input. Continuing these medications beyond the acute phase delays recovery and prolongs symptoms.

Corticosteroids for Hearing Preservation

Oral prednisone is started as early as possible, ideally within the first 72 hours of symptom onset, to reduce inflammation and improve the chance of hearing recovery. The mechanism parallels that used in sudden sensorineural hearing loss (SSNHL), as the cochlear component of labyrinthitis is essentially an inflammatory cause of sudden hearing loss. The typical regimen is prednisone 1 mg/kg/day (maximum 60 mg/day) for 7-14 days followed by a taper over 5-7 days.

If oral steroids fail to produce hearing recovery, intratympanic dexamethasone injection may be considered as salvage therapy. This delivers a high concentration of steroid directly to the round window membrane and into the inner ear. This is more commonly studied in isolated SSNHL, but the principle extends to the cochlear injury in labyrinthitis.

Vestibular Rehabilitation

Once acute nausea and vertigo begin to subside (typically after day 3-5), the patient should be started on a structured vestibular rehabilitation program. This is the cornerstone of long-term recovery. Exercises include gaze stabilization (head movement while maintaining visual fixation on a target), habituation exercises (repeated exposure to provocative movements), and balance retraining. Central compensation is an active process that requires vestibular challenge, which is why stopping suppressant medications and starting rehabilitation early is essential.

Bacterial Labyrinthitis

When bacterial extension from the middle ear is suspected (concurrent otitis media, otorrhea, fever), intravenous antibiotics must be started urgently. Ceftriaxone or a combination covering typical middle ear pathogens (S. pneumoniae, H. influenzae, Moraxella) is appropriate. Surgical intervention such as myringotomy with tube placement or mastoidectomy may be necessary to drain the source of infection and prevent further intracranial complications (meningitis, brain abscess, lateral sinus thrombosis).

In meningogenic labyrinthitis, treatment of the underlying meningitis takes priority. Dexamethasone administered before or concurrently with the first dose of antibiotics has been shown to reduce the incidence of hearing loss in pneumococcal meningitis. Serial audiometry should be performed, and if profound bilateral hearing loss develops, early cochlear implant evaluation is critical because labyrinthine ossification can begin within weeks, making future implantation technically difficult or impossible.

Contraindications and Cautions

Corticosteroids should be used cautiously in patients with uncontrolled diabetes, active peptic ulcer disease, or immunocompromised states. In diabetic patients, close glucose monitoring during the steroid course is necessary, and the potential benefit of hearing preservation must be weighed against the metabolic risks.

Benzodiazepines carry risks of sedation, respiratory depression, and dependence. In elderly patients, meclizine is generally preferred over diazepam due to the lower risk of falls and oversedation.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common trap on this topic is the failure to distinguish labyrinthitis from vestibular neuritis. Both present with acute continuous vertigo, unidirectional nystagmus, and a positive head impulse test. The single discriminating feature is hearing loss. If the vignette mentions any degree of sensorineural hearing loss or tinnitus alongside acute vertigo, the answer is labyrinthitis. If hearing is explicitly normal, the answer is vestibular neuritis. Students who do not actively look for this detail in the stem will conflate the two diagnoses.

A second high-yield trap involves the AICA stroke mimic. The anterior inferior cerebellar artery gives off the labyrinthine artery, which supplies the inner ear. An AICA territory infarct can produce acute vertigo with ipsilateral hearing loss, looking identical to labyrinthitis on the surface. The exam tests whether you can apply the HINTS examination (Head Impulse, Nystagmus, Test of Skew) to differentiate peripheral from central causes. A negative head impulse test (no corrective saccade) in a patient with acute vertigo is a red flag for stroke, not a reassuring finding. This is counterintuitive and is a favorite test question.

A third pitfall is over-treating with vestibular suppressants. The vignette may describe a patient one week into labyrinthitis who is still taking meclizine three times daily and has not improved. The correct next step is to discontinue the suppressant and initiate vestibular rehabilitation, not to increase the medication dose or switch to a different suppressant.

Finally, in the setting of bacterial meningitis complicated by hearing loss, students must recognize the urgency of cochlear implant evaluation. Labyrinthine ossification can begin within weeks of meningitis, and a delay in imaging and referral may render the patient ineligible for implantation. When the vignette describes a post-meningitic child with bilateral profound hearing loss, the next step is temporal bone imaging and otologic referral, not a "wait and observe" approach.

The core competency being tested across labyrinthitis questions is the ability to localize an acute vestibular syndrome to the peripheral system using bedside examination, to identify cochlear involvement as the distinguishing feature from vestibular neuritis, and to recognize the one dangerous central mimic that can present with both vertigo and hearing loss.