Vestibular Function Testing for Vertigo Evaluation
Direct Answer
The primary tests to evaluate vertigo are Electronystagmography (ENG) and Videonystagmography (VNG), which assess the vestibular-ocular reflex by recording involuntary eye movements (nystagmus) in response to various stimuli. 1
Understanding ENG and VNG
Both ENG and VNG serve the same diagnostic purpose but use different recording technologies:
- ENG uses electrodes placed around the eyes to detect the corneoretinal potential and record eye movements 2
- VNG uses infrared cameras to directly visualize and record eye movements, offering technical advantages over ENG 3
- VNG is superior to ENG for discriminating between peripheral and central vestibular lesions, as it more accurately identifies canal paresis without false positives that can occur with ENG 4
Test Components
The ENG/VNG battery includes several specialized assessments:
- Caloric testing using warm and cool water or air irrigation of the ear canals to stimulate the lateral semicircular canals and induce nystagmus 1, 2
- Voluntary eye movement tracking to assess oculomotor function 1
- Positional testing to record nystagmus during head and body position changes 1
- Spontaneous nystagmus evaluation to detect baseline abnormalities 5
When to Order These Tests
Do NOT order ENG/VNG routinely for clear clinical diagnoses:
- BPPV with typical presentation (brief positional vertigo, positive Dix-Hallpike maneuver) does not require vestibular testing 1, 6
- Ménière's disease with classic symptoms (episodic vertigo, hearing loss, tinnitus, aural fullness) does not need routine testing 1
- Vestibular neuritis with clear clinical features requires no additional testing if diagnosis is straightforward 7
DO order ENG/VNG when:
- Diagnosis remains unclear after history and physical examination 1, 7
- Clinical presentation is atypical for common vestibular disorders 1, 7
- Positional testing produces equivocal or unusual nystagmus patterns that don't fit typical BPPV 1
- Additional neurological symptoms suggest CNS or otologic pathology beyond simple peripheral vestibular dysfunction 1, 7
- Multiple concurrent vestibular disorders are suspected 1
- Treatment failure occurs after appropriate therapy (e.g., failed canalith repositioning for presumed BPPV) 1
- Frequent recurrences of vertigo episodes suggest more complex pathology 1
Additional Vestibular Tests
Beyond ENG/VNG, other specialized tests may be appropriate:
- Video Head Impulse Test (vHIT) assesses high-frequency vestibular-ocular reflex function during rapid head rotations, useful for vestibular neuritis and superior canal dehiscence 1
- Vestibular Evoked Myogenic Potentials (VEMP) evaluate otolith organ function (saccule and utricle) not assessed by traditional tests 1
Critical Pitfalls to Avoid
- Unnecessary testing delays diagnosis and treatment while increasing costs to patients and healthcare systems 1, 7
- Normal vestibular test results do NOT rule out vestibular disorders, as test results fluctuate throughout disease course and correlate poorly with patient-perceived disability 1, 7
- Patient discomfort is significant during testing, including nausea and vertigo provocation 1
- Tests should guide treatment planning, not be ordered reflexively as part of a "vertigo workup" 7, 6
- Results must be interpreted in clinical context, not in isolation, as abnormalities may not correlate with symptom severity 1
Algorithmic Approach
- Perform thorough history and physical examination including Dix-Hallpike and supine roll tests 6
- If diagnosis is clear (typical BPPV, classic Ménière's, straightforward vestibular neuritis): treat without testing 1, 7, 6
- If diagnosis is unclear, presentation atypical, or treatment fails: order ENG/VNG 1, 7
- If neurological red flags present (diplopia, dysarthria, ataxia, focal weakness): obtain MRI brain before or concurrent with vestibular testing 7, 6
- Reserve specialized tests (vHIT, VEMP) for specific clinical scenarios requiring additional information about vestibular function 1