What is the diagnostic and treatment approach for patients undergoing VNG (Vestibular Nystagmus Test) testing for dizziness and vertigo?

Diagnostic and Treatment Approach for VNG Testing in Dizziness and Vertigo

Videonystagmography (VNG) testing should NOT be routinely performed in patients who meet clinical criteria for BPPV but should be reserved for cases with unclear diagnosis, atypical presentations, or additional vestibular symptoms that cannot be explained by BPPV alone. 1

When to Use VNG Testing

Appropriate Indications:

• When the diagnosis of vertiginous or dizziness syndrome is unclear 1
• When patients remain symptomatic following treatment for BPPV 1
• When multiple concurrent peripheral vestibular disorders are suspected 1
• When clinical presentation is atypical or Dix-Hallpike testing elicits equivocal/unusual nystagmus findings 1
• When additional symptoms beyond those attributable to BPPV are present 1

Inappropriate Indications:

• Routine confirmation of BPPV when clinical criteria are already met 1
• As first-line testing before performing basic clinical maneuvers like Dix-Hallpike test 1

Diagnostic Algorithm

Step 1: Initial Clinical Assessment

• Categorize dizziness based on timing and triggers:
  • Acute vestibular syndrome
  • Triggered episodic vestibular syndrome
  • Spontaneous episodic vestibular syndrome
  • Chronic vestibular syndrome 2

Step 2: Perform Specific Bedside Tests

• Dix-Hallpike test for suspected BPPV 1, 3
• HINTS examination (Head-Impulse, Nystagmus, Test of Skew) to differentiate central from peripheral causes 2

Step 3: Determine Need for VNG Testing

• If diagnosis remains unclear after bedside tests
• If atypical features are present
• If multiple vestibular disorders are suspected

Components of VNG Testing

VNG testing involves specialized tests that record nystagmus in response to labyrinthine stimulation and voluntary eye movements, primarily focusing on the vestibular-ocular reflex 1. Key components include:

• Bithermal caloric testing (using 30°C and 44°C air irrigations) 4
• Measurement of nystagmus frequency (FRQ) and slow phase velocity (SPV) 4
• Assessment of canal paresis (CP) and directional preponderance (DP) 4
• Evaluation of vestibular excitability (VE) 4

Interpreting VNG Results

Peripheral Vestibular Disorders:

• Significant canal paresis (CP) is typically identified in peripheral disorders such as vestibular neuritis 4
• Benign paroxysmal positional vertigo (BPPV) may show specific patterns based on affected canal 3

Central Vestibular Disorders:

• Directional preponderance (DP) is more commonly observed 4
• Absence of canal paresis in VNG is suggestive of central origin 4

Treatment Approach Based on VNG Findings

For BPPV:

• Canalith repositioning procedures (CRPs) based on the affected canal:
  • Epley maneuver or Semont maneuver for posterior canal BPPV 2
  • Specific maneuvers for horizontal or anterior canal involvement

For Other Vestibular Disorders:

• Vestibular rehabilitation for chronic symptoms or vestibular neuritis 2
• Short-term vestibular suppressants for symptomatic management 2
• Treatment of underlying cause when identified (e.g., Menière's disease, vestibular migraine)

Important Caveats and Pitfalls

• VNG results do not always correlate with symptom severity or disability scores 5
• No statistically significant association exists between VNG test and Sensory Organization Test results, emphasizing the different aspects tested by each 6
• VNG and cVEMP results may differ between adults and children, requiring age-appropriate interpretation 7
• Routine neuroimaging is not recommended for typical BPPV with positive Dix-Hallpike test and no atypical features 2
• VNG testing adds significant cost to diagnosis and management of BPPV and should be used judiciously 1

When to Consider Additional Testing

• MRI brain (without contrast) is indicated for:

  • Acute Vestibular Syndrome with abnormal HINTS examination
  • Vestibular symptoms with neurological deficits
  • High vascular risk patients with Acute Vestibular Syndrome
  • Chronic undiagnosed dizziness not responding to treatment 2

• Consider ECG for patients with:

  • Unexplained dizziness
  • Signs of structural heart disease
  • Cardiac arrhythmia 2

By following this diagnostic and treatment approach, clinicians can appropriately utilize VNG testing to improve outcomes for patients with dizziness and vertigo while avoiding unnecessary testing.