Can labyrinthitis be diagnosed through any tests, such as electronystagmography (ENG) or videonystagmography (VNG), audiometry, or magnetic resonance imaging (MRI)?

Diagnostic Testing for Labyrinthitis

Labyrinthitis is primarily a clinical diagnosis that does not show up on any specific test, though certain diagnostic studies may help rule out other conditions or support the diagnosis indirectly.

Clinical Diagnosis of Labyrinthitis

Labyrinthitis is diagnosed primarily through clinical presentation and examination, with testing serving to rule out other conditions rather than directly confirming labyrinthitis.

Key Clinical Features

• Sudden onset of vertigo
• Hearing loss (sensorineural)
• Tinnitus
• Nausea and vomiting
• Imbalance
• Nystagmus on examination

Diagnostic Testing Approach

Audiometric Testing

• Audiogram: May demonstrate sensorineural hearing loss in affected ear 1
• This test is essential for establishing baseline hearing status and monitoring recovery
• Does not diagnose labyrinthitis specifically but supports the diagnosis

Vestibular Function Testing

• Electronystagmography (ENG)/Videonystagmography (VNG): May show vestibular weakness on the affected side
• Video Head Impulse Test (vHIT): May demonstrate reduced vestibular function
• Vestibular Evoked Myogenic Potentials (VEMP): May show abnormal responses
• Rotary Chair Testing: May indicate vestibular hypofunction

These tests should not be routinely ordered just to establish the diagnosis of labyrinthitis 1. They may be useful when:

• Diagnosis is uncertain
• Symptoms persist despite treatment
• Multiple vestibular disorders are suspected

Imaging Studies

• MRI with contrast:

  • Not routinely needed but may show enhancement of the labyrinth in acute cases 2
  • Can exclude other causes of vertigo (vestibular schwannoma, multiple sclerosis, stroke)
  • Specialized sequences like CISS or FIESTA can better visualize inner ear structures 3
  • May show intense labyrinthine enhancement in bacterial labyrinthitis 2

• CT Temporal Bone:

  • Not useful for direct visualization of labyrinthitis
  • May help identify complications like middle ear infection or mastoiditis 4
  • Better for visualizing bony structures rather than soft tissue inflammation 3

Diagnostic Algorithm

1. Initial Evaluation:

   • Detailed history focusing on onset, duration, and associated symptoms
   • Otoscopic examination to identify middle ear infection
   • Neurological examination including nystagmus evaluation

2. First-line Testing:

   • Audiogram to document hearing loss pattern and severity

3. Second-line Testing (if diagnosis uncertain or symptoms atypical):

   • MRI with contrast using dedicated IAC protocol with high-resolution T2-weighted sequences
   • Vestibular function testing (VNG/ENG)

4. Additional Testing (for suspected complications):

   • CT temporal bone (for suspected bony involvement)
   • Laboratory tests (if infectious or autoimmune etiology suspected)

Prognosis and Monitoring

• Hearing recovery occurs in only about 20% of cases with idiopathic labyrinthitis 5
• Balance problems may persist in up to 72.5% of patients even after years of follow-up 5
• Serial audiometry can be used to monitor hearing recovery

Common Pitfalls

• Misdiagnosis: Labyrinthitis can be confused with vestibular neuritis (which spares hearing), BPPV, or Ménière's disease
• Delayed diagnosis of complications: Bacterial labyrinthitis can lead to meningitis if not promptly treated 4
• Overreliance on testing: Remember that labyrinthitis remains primarily a clinical diagnosis
• Inadequate imaging protocols: Standard MRI head protocols may miss inner ear abnormalities; dedicated IAC protocols are required 3
• Missing underlying causes: Labyrinthitis may be secondary to middle ear infections, which require specific treatment 6

In conclusion, while no test definitively shows labyrinthitis, a combination of clinical evaluation and selective testing can support the diagnosis and rule out other conditions, guiding appropriate treatment decisions.