Labyrinthitis

Labyrinthitis
Other Names	Otitis interna, Inner ear infection
Identifiers
ICD-9	386.30
ICD-10	H83.0
MeSH	D007762
Outside Resources
Radiopaedia	Labyrinthitis

Overview

Labyrinthitis is an acute inflammatory condition affecting the membranous labyrinth, involving both the vestibular and cochlear portions of the inner ear. The condition presents with acute vertigo, hearing loss, and tinnitus, distinguishing it from Vestibular Neuritis, which affects only the vestibular nerve and spares hearing.

Labyrinthitis may be caused by viral or bacterial infections, with viral labyrinthitis being more common. Bacterial labyrinthitis is a serious condition that may arise from otitis media or meningitis and can lead to permanent cochlear and vestibular damage if not promptly treated. The distinction between viral and bacterial etiologies is critical for appropriate management, as is the distinction between serous (toxic) and suppurative labyrinthitis.

History

The term "labyrinthitis" derives from the anatomical labyrinth of the inner ear. Historically, the condition was recognized as a complication of otitis media and meningitis, often with devastating consequences including deafness and death. The distinction between serous (toxic) and suppurative labyrinthitis was established in the pre-antibiotic era.

With the introduction of antibiotics in the mid-20th century, suppurative labyrinthitis became less common and less often fatal. Viral labyrinthitis and vestibular neuritis emerged as more commonly recognized clinical entities. The development of audiometry and vestibular function testing allowed for more precise characterization of these conditions.

Pathophysiology

Relevant Anatomy

Bony labyrinth:

• Cochlea: Spiral structure (2.5-2.75 turns) containing organ of Corti for hearing
• Vestibule: Contains utricle and saccule (otolith organs) for linear acceleration and gravity detection
• Semicircular canals: Three canals (superior, posterior, lateral) detecting angular acceleration

Membranous labyrinth:

• Contained within bony labyrinth, filled with endolymph (high K+, low Na+)
• Cochlear duct (scala media): Contains hair cells for hearing
• Utricle and saccule: Linear acceleration and gravity detection
• Semicircular canal ampullae: Angular acceleration detection via crista ampullaris

Vestibular nerve:

• Superior division: Innervates superior and lateral semicircular canals, utricle
• Inferior division: Innervates posterior semicircular canal, saccule

Cochlear nerve:

• Innervates organ of Corti via spiral ganglion neurons
• Transmits auditory information to cochlear nuclei in brainstem

Blood supply:

• Labyrinthine artery (branch of AICA, occasionally PICA): Sole blood supply to inner ear
• Vulnerable to ischemia; no collateral circulation
• Divides into anterior vestibular artery, vestibulocochlear artery, and cochlear artery

• 

  Bony Labyrinth anatomy

Disease Etiology

Classification by etiology:

Viral Labyrinthitis

Viral labyrinthitis is the most common form.

Associated viruses:

• Herpes simplex virus (HSV-1): Most commonly implicated virus in vestibular neuritis
• Varicella-zoster virus (VZV): Causes Ramsay-Hunt syndrome (herpes zoster oticus) with facial palsy, otalgia, and vesicles
• Cytomegalovirus (CMV): Particularly in immunocompromised patients
• Epstein-Barr virus (EBV)
• Mumps, measles, rubella
• Influenza viruses
• Respiratory syncytial virus (RSV)
• Adenovirus

Pathophysiology: Direct viral invasion of labyrinthine structures or immune-mediated inflammation following viral infection. Often follows upper respiratory infection by 1-2 weeks.

Bacterial Labyrinthitis

Tympanogenic (from otitis media):

• Extension from acute or chronic otitis media through round window membrane or oval window
• May occur via labyrinthine fistula (e.g., from cholesteatoma erosion)
• Pathogens: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Pseudomonas aeruginosa

Meningogenic (from meningitis):

• Bacteria enter via cochlear aqueduct or internal auditory canal
• Often bilateral involvement
• Pathogens: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae

Serous vs. Suppurative Labyrinthitis

Serous (toxic) labyrinthitis: Bacterial toxins and inflammatory mediators (cytokines, enzymes, complement) cross the round window membrane into the labyrinth without direct bacterial invasion; may be reversible if treated promptly with antibiotics and corticosteroids.

Suppurative labyrinthitis: Direct bacterial invasion of the labyrinth with purulent infection; nearly always results in permanent and profound hearing loss.

Other Causes

• Autoimmune inner ear disease (AIED)
• Trauma (temporal bone fracture, barotrauma)
• Ototoxicity (aminoglycosides, cisplatin)
• Post-surgical

Diagnosis

Patient History

Acute presentation (distinguishes from Ménière's disease):

Vestibular symptoms:

• Vertigo: Sudden onset, severe, room-spinning sensation lasting days to weeks
• Nausea and vomiting: Often prominent, especially early
• Gait instability: Difficulty walking, falls toward affected side
• Duration: Days to weeks (unlike BPPV which lasts seconds to minutes)

Auditory symptoms (KEY distinguishing feature from vestibular neuritis):

• Hearing loss: Typically unilateral sensorineural; may range from mild to profound
• Tinnitus: Ipsilateral to affected ear, often prominent
• Aural fullness: Sensation of ear blockage

Associated symptoms indicating specific etiology:

• Recent upper respiratory infection (viral labyrinthitis)
• Ear pain, otorrhea, fever (bacterial/otogenic)
• Headache, neck stiffness, photophobia (meningogenic)
• Facial weakness, vesicles on ear (Ramsay-Hunt syndrome)

Physical Examination

Vestibular examination:

• Spontaneous nystagmus: Horizontal or horizontal-torsional; fast phase beats away from affected side; suppressed by visual fixation (peripheral pattern)
• Head impulse test (HIT): Abnormal toward affected side with corrective catch-up saccade
• Romberg test: Fall toward affected side
• Gait: Deviation toward affected side
• Fukuda stepping test: Rotation toward affected side

Otoscopy:

• Normal (viral labyrinthitis)
• Acute otitis media, tympanic membrane perforation, cholesteatoma (bacterial)
• Vesicles on external ear/concha (Ramsay-Hunt syndrome)
• Mastoid tenderness (if mastoiditis)

Hearing assessment:

• Rinne test: Air conduction > bone conduction bilaterally (sensorineural loss pattern)
• Weber test: Lateralizes to unaffected ear

Cranial nerve examination:

• Facial nerve (VII): Assess for Ramsay-Hunt syndrome
• Other cranial nerves if meningitis suspected

Laboratory Tests

Routine labs:

• CBC: Leukocytosis suggests bacterial infection
• Inflammatory markers (CRP, ESR)

Specific tests:

• Blood cultures (if septic or bacterial etiology suspected)
• Lumbar puncture (if meningitis suspected)
• Viral serology (rarely changes acute management)

Imaging

MRI with Gadolinium

MRI is indicated when bacterial labyrinthitis, retrocochlear pathology, or atypical presentation is suspected.

Preferred sequence: 3D-FLAIR (pre- and post-contrast) is the optimal sequence for detecting labyrinthitis, identifying underlying labyrinthine conditions in 24-57% of patients with sudden sensorineural hearing loss.

Characteristic MRI findings:

• High signal intensity on 3D-FLAIR in vestibule (most common), cochlea, and/or semicircular canals
• Enhancement of labyrinthine structures on post-contrast T1-weighted images
• Enhancement of vestibular and/or cochlear nerves
• CISS hypointensity of inner ear structures (found in 40% of labyrinthitis cases versus 5% in Ménière's disease)
• Correlation between MRI findings and symptomatic side

Exclusion of other pathology: Acoustic neuroma, cerebellopontine angle tumors, brainstem stroke, demyelinating disease.

High-Resolution CT Temporal Bone

Indicated when bacterial labyrinthitis is suspected:

• Cholesteatoma with labyrinthine fistula
• Mastoiditis
• Bony erosion
• Labyrinthitis ossificans (late complication)

Audiometry

Essential test for confirming hearing loss and distinguishing labyrinthitis from vestibular neuritis.

• Documents type and degree of sensorineural hearing loss (mild to profound)
• Important for baseline and follow-up monitoring
• Speech discrimination testing

Vestibular Function Testing

• Video head impulse test (vHIT): Quantifies VOR gain; abnormal toward affected side
• Videonystagmography (VNG): Documents nystagmus characteristics
• Caloric testing: Shows reduced vestibular response (canal paresis) on affected side
• May be deferred in acute phase due to patient discomfort

Prognostic value of vHIT: Posterior semicircular canal involvement (ipsilesional posterior canal gain <0.65) is associated with poorer hearing recovery.

Differential Diagnosis

• Vestibular Neuritis (no hearing loss)
• Ménière's disease (episodic, fluctuating hearing loss)
• Benign paroxysmal positional vertigo (brief episodes, positional triggers)
• Acoustic neuroma (gradual onset, asymmetric hearing loss)
• Brainstem stroke (central signs: direction-changing nystagmus, vertical nystagmus, normal HIT)
• Multiple sclerosis
• Perilymphatic fistula
• Superior semicircular canal dehiscence
• Otosyphilis
• Autoimmune inner ear disease

Management

Medical Management

Viral Labyrinthitis

Symptomatic treatment (short-term use only, 2-3 days):

• Vestibular suppressants:
  • Meclizine 25-50 mg PO q6-8h
  • Dimenhydrinate 50 mg PO q6h
  • Diazepam 2-5 mg PO q8h (for severe symptoms)
• Antiemetics:
  • Ondansetron 4-8 mg PO/IV q8h
  • Promethazine 25 mg PO/PR q6h

Important: Vestibular suppressants should be discontinued after 2-3 days as they impair central compensation.

Corticosteroids:

Corticosteroids improve vestibular function recovery but evidence for symptomatic benefit is limited, supporting shared decision-making rather than routine use.

Evidence for corticosteroids:

• Physiologic benefit: Methylprednisolone significantly improves peripheral vestibular function recovery (OR 3.1 for good acute outcomes; OR 2.4 for restoration of vestibular function at follow-up)
• The landmark Strupp NEJM trial showed mean improvement in vestibular paresis of 62.4% with methylprednisolone versus 39.6% with placebo at 12 months (P<0.001)
• Symptomatic benefit: No clear benefit demonstrated for symptomatic recovery or quality of life
• NNT/NNH: Number needed to treat is 6-7; number needed to harm (adverse effects) is only 4

If corticosteroids are used:

• Methylprednisolone 100 mg IV daily × 3 days, then oral taper over 3 weeks; OR
• Prednisone 1 mg/kg/day (max 60 mg) × 5-7 days, then taper

Antiviral therapy:

Randomized controlled trials show no benefit from antiviral therapy in viral labyrinthitis/vestibular neuritis, even when HSV-1 is the presumed etiology.

• The Strupp NEJM trial definitively demonstrated that valacyclovir does not improve outcomes (P=0.43)
• Mean improvement with valacyclovir alone (36.0%) was essentially identical to placebo (39.6%)
• Adding valacyclovir to methylprednisolone provides no additional benefit over steroids alone

Exception: Ramsay-Hunt syndrome (VZV) may benefit from antivirals (valacyclovir 1000 mg PO TID × 7 days) combined with corticosteroids.

Bacterial Labyrinthitis

Urgent treatment required:

Antibiotics:

• IV broad-spectrum antibiotics with CNS penetration
• Empiric regimen: Ceftriaxone 2g IV daily + Vancomycin 15-20 mg/kg IV q8-12h
• Duration: 2-4 weeks depending on source and response
• Adjusted based on culture and sensitivity results

Corticosteroids:

• May help preserve hearing in bacterial labyrinthitis
• Dexamethasone 0.15 mg/kg IV q6h often used as adjunct, especially in meningogenic cases

Surgical Management

Indications for surgery (bacterial labyrinthitis):

• Mastoiditis requiring mastoidectomy (see Acute Mastoiditis, Bezold Abscess)
• Cholesteatoma removal
• Labyrinthine fistula repair
• Meningitis source control

Vestibular Rehabilitation

Vestibular rehabilitation therapy (VRT) is an essential component of recovery and should be initiated within the first 2 weeks for optimal outcomes.

Evidence for early VRT:

• Early vestibular rehabilitation (within 14 days) significantly improved Dizziness Handicap Inventory scores by -7.18 points (95% CI -10.48 to -3.88)
• VRT started early significantly reduced perceived dizziness at 3 months (p=0.007) and 12 months (p=0.001)
• Improved balance with eyes closed and reduced anxiety/depression measures

VRT components:

• Gaze stabilization exercises: VOR adaptation and substitution
• Balance training: Static and dynamic balance, proprioceptive exercises
• Habituation exercises: Desensitization to provocative movements
• Walking and gait training

Program duration: Supervised program typically 4-8 weeks; home exercises continued long-term.

Outcomes

Complications

Vestibular:

• Persistent vestibular hypofunction
• Chronic imbalance and oscillopsia
• Secondary benign paroxysmal positional vertigo

Auditory:

• Permanent sensorineural hearing loss
• Chronic tinnitus

Bacterial labyrinthitis complications:

• Meningitis
• Intracranial abscess (epidural, subdural, brain abscess)
• Labyrinthitis ossificans: Fibrosis and ossification of labyrinth; may preclude cochlear implantation
• Complete labyrinthine loss (dead ear)

Prognosis

Viral Labyrinthitis

Vestibular recovery: Generally favorable with 80-90% achieving functional recovery within 3-6 weeks through central vestibular compensation.

Hearing recovery: More variable than vestibular recovery.

• Only 20% achieve subjective hearing recovery in some studies
• Other studies report 0-80% partial recovery
• Hearing recovery is less predictable than vestibular recovery

Chronic symptoms: Residual dizziness or imbalance persists in 10-20% of patients, requiring extended vestibular rehabilitation.

Poor prognostic factors for hearing recovery:

• Abnormal inferior vestibular function (posterior canal involvement)
• Ipsilesional posterior canal gain <0.65 on video head impulse test (vHIT)
• Initial hearing loss >60 dB
• Older age

Bacterial Labyrinthitis

More guarded prognosis:

Serous (toxic) labyrinthitis:

• Potentially reversible with early aggressive treatment (antibiotics + corticosteroids)
• Contemporary case reports demonstrate complete hearing recovery is possible when treated promptly

Suppurative labyrinthitis:

• Nearly always results in profound permanent hearing loss
• Early treatment with antibiotics significantly improves survival but rarely preserves hearing
• Labyrinthitis ossificans may develop within weeks to months, potentially precluding cochlear implantation

Factors affecting recovery:

• Age (younger patients compensate better due to superior neuroplasticity)
• Timing of vestibular rehabilitation (early initiation within 2 weeks accelerates recovery)
• Pre-existing vestibular dysfunction or hearing loss
• Completeness of labyrinthine destruction
• Compliance with rehabilitation therapy
• Underlying etiology (viral vs. bacterial; serous vs. suppurative)