Vestibular Assessment Using Electronystagmography (ENG) and Videonystagmography (VNG)

Introduction to ENG and VNG

• The American Academy of Otolaryngology-Head and Neck Surgery recommends that both ENG and VNG are designed to assess the integrity of the vestibular system by evaluating the vestibular-ocular reflex, which is the neurological relationship between eye movements and the balance organs 1

Key Components of ENG/VNG Testing

• The American Academy of Otolaryngology-Head and Neck Surgery suggests that both tests typically include a battery of specialized assessments that record nystagmus (involuntary rhythmic eye movements) in response to labyrinthine stimulation (caloric testing using warm and cool water or air in the ear canals) 2
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that both tests typically include a battery of specialized assessments that record nystagmus (involuntary rhythmic eye movements) in response to voluntary eye movements 3
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that both tests typically include a battery of specialized assessments that record nystagmus (involuntary rhythmic eye movements) in response to positional changes 4

Clinical Applications

• The American Academy of Otolaryngology-Head and Neck Surgery recommends that these tests are valuable for quantifying vestibular dysfunction 1
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that these tests are valuable for providing information for treatment planning 1

When to Use ENG/VNG Testing

• The American Academy of Otolaryngology-Head and Neck Surgery recommends that ENG/VNG testing is not recommended as routine tests for conditions with clear clinical diagnoses such as Benign Paroxysmal Positional Vertigo (BPPV) when diagnostic criteria are met 4
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that ENG/VNG testing is not recommended as routine tests for conditions with clear clinical diagnoses such as Ménière's disease with typical history and symptoms 5
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that ENG/VNG testing is appropriate for use when diagnosis of vertigo/dizziness is unclear 1
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that ENG/VNG testing is appropriate for use when clinical presentation is atypical 6
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that ENG/VNG testing is appropriate for use when positional testing elicits equivocal or unusual nystagmus 6
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that ENG/VNG testing is appropriate for use when additional symptoms suggest accompanying CNS or otologic disorders 6
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that ENG/VNG testing is appropriate for use when multiple concurrent peripheral vestibular disorders are suspected 6
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that ENG/VNG testing is appropriate for use when patients remain symptomatic following treatment 1

Common Pitfalls and Caveats

• The American Academy of Otolaryngology-Head and Neck Surgery recommends that unnecessary vestibular testing can lead to delays in diagnosis and treatment 5
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that unnecessary vestibular testing can lead to increased direct and indirect costs to patients and providers 5
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that results of vestibular testing often fluctuate throughout the course of vestibular disorders like Ménière's disease, and the degree of damage detected correlates poorly with patient-perceived disability 5
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that normal vestibular test results do not necessarily rule out vestibular disorders like Ménière's disease 5
• The American Academy of Otolaryngology-Head and Neck Surgery recommends that patient discomfort including nausea and vertigo during testing should be considered 2

Vestibular Function Testing and Treatment

Clinical Features Supporting Comprehensive Testing

• The American Academy of Otolaryngology-Head and Neck Surgery recommends comprehensive vestibular function testing in patients with atypical clinical presentation, suspected additional vestibular pathology, failed response to canalith repositioning procedures, or frequent recurrences of BPPV, which was the case for this patient with multiple episodes of severe vertigo, prolonged fatigue, and heavy-headedness 7, 8, 9.
• Patients with recurrent symptoms, such as this patient who experienced similar episodes 6-7 years prior and multiple episodes through September 2024, have a higher likelihood of additional vestibular pathology (25-50% of recurrent cases) 9.
• Unclear diagnosis requiring differentiation, such as this patient who had been evaluated by multiple providers without definitive diagnosis, and had an incidental finding of an arachnoid cyst on MRI, warrants comprehensive testing 7.
• Failed response to initial physical therapy, as seen in this patient who underwent PT in September 2024 without benefit, suggests the diagnosis was unclear or treatment was inadequate, and comprehensive testing is necessary 9.

Guideline Support for Testing

• The American Academy of Otolaryngology-Head and Neck Surgery explicitly states that comprehensive vestibular function testing is warranted in patients with atypical nystagmus, suspected additional vestibular pathology, failed response to canalith repositioning procedures, or frequent recurrences of BPPV, which applies to this patient 9.
• The guidelines recommend against routine vestibular testing only when patients meet clear diagnostic criteria for BPPV without additional symptoms, which was not the case for this patient 7.

Clinical Presentation and Testing

• Simple BPPV presents with brief (seconds) episodes of vertigo triggered by specific head positions, responds to canalith repositioning, and does not require comprehensive testing, whereas this patient had prolonged episodes (hours), failed initial PT, recurrent symptoms over years, and abnormal findings on multiple vestibular tests 7, 8, 9.
• The patient's clinical presentation, including prolonged vertigo episodes, lack of clear positional component, failed PT, recurrent nature, and incidental brain imaging findings, made the diagnosis unclear and testing appropriate 7, 8, 9.

Vestibular Function Testing: A Comprehensive Clinical Guide

Overview of Vestibular Function Testing

• Vestibular function testing comprises a battery of specialized diagnostic procedures that evaluate the vestibular-ocular reflex to diagnose and characterize balance disorders when clinical diagnosis remains unclear, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 10, 11, 12
• The primary purpose of these tests is to record nystagmus in response to labyrinthine stimulation and voluntary eye movements, providing quantitative information about vestibular reflexes, central oculomotor function, and postural control strategies 10

Indications for Vestibular Function Testing

• Vestibular function testing is indicated when diagnosis of vertigo/dizziness syndrome is unclear after history and physical examination, as suggested by the American Academy of Otolaryngology-Head and Neck Surgery 10
• Testing is also indicated when clinical presentation is atypical for common vestibular disorders, or when additional neurological symptoms suggest accompanying CNS or otologic disorders beyond typical vestibular presentations 10, 11, 12

Individual Vestibular Function Tests

• Electronystagmography (ENG) and Videonystagmography (VNG) are foundational vestibular assessment tools that evaluate the vestibular-ocular reflex through comprehensive recording of eye movements in response to various stimuli, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 10
• The Video Head Impulse Test (vHIT) is a modern, noninvasive method that assesses high-frequency vestibulo-ocular reflex function by measuring compensatory eye movements during rapid head rotations, with applications in diagnosing vestibular neuritis and superior canal dehiscence syndrome 11
• Vestibular Evoked Myogenic Potentials (VEMP) testing evaluates otolith organ function by measuring muscle responses to acoustic or vibration stimuli, providing information about structures not assessed by traditional vestibular tests, such as the saccule and utricle 11

Evidence-Based Testing Algorithm

• The American Academy of Otolaryngology-Head and Neck Surgery emphasizes the importance of a step-wise approach to vestibular testing, starting with clinical assessment and proceeding to specific tests based on clinical scenario and presence of red flags 10, 11, 12
• Testing should be reserved for situations where results will meaningfully impact diagnostic accuracy, treatment planning, or monitoring, and should be interpreted in the context of clinical findings rather than in isolation 10, 11