VNG-Findings-Treatments

VNG-Findings-Treatments - Interpretation of Video...

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Unformatted text preview: Interpretation of Video Electronystagmography (VNG) Elliot Michel, M.D. Neurology Background VENG provides an objective assessment of the oculomotor and vestibular systems VENG test battery consists of 4 parts: Oculomotor evaluation Tracking, Saccades, Optokinetic, Active Head Rotation, Spontaneous Gaze, Torsion Swing. Positional testing Dix-Hallpike, Supine Head (Center, Left, Right) Supine Body (Left, Right) Caloric stimulation Background The comparison of results obtained from various subtests of VENG assists in determining whether a disorder is central or peripheral . Central findings should be correlated with neuroimmaging. Peripheral findings can be treated with canalith repositional maneuvers (CRM), and/or vestibular rehabilitation therapy (VRT). In peripheral vestibular disorders, the side of lesion can be inferred from the results of caloric stimulation and, to some degree, from positional findings. Background Medications Many medications can affect test results. Patients should discontinue medications, unless contraindicated, for 48 hours prior to testing. sleeping pills, tranquilizers, barbiturates, antihistamines, anti-dizzy medications, anti-depresants, ETOH Any medications taken should be clearly noted on the test results. Alcohol ingestion can affect ENG test results for 72 hours post ingestion (agonist or antagonist). Patient Instructions-Practical Considerations Why stop medications? What about long-term users? Why stop alcohol? Why 48 hours for medications and alcohol? What about tobacco and caffeine? What if the patient does not comply? Patient Interview Develop rapport with the patient Explain the test in an honest and reassuring manor without using misleading or threatening language Ask about recent medication and alcohol use Obtain clinical information- Heart/circulation problems?- Seizures?- Severe hearing impairment? - Ear surgery?- Severe visual problems?- Positional vertigo?- Child/mentally retarded? - Head trauma?- VNG vs. ENG: Resolution VNG-Resolution of about 0.1-In laboratory conditions, can detect movements as small as 0.5 ENG-Resolution of about 1-In laboratory conditions, cannot detect movements of less than 2-3 Practical Implication-VNG can measure smaller amplitude of eye movements. VNG vs. ENG: Type of Eye Movements VNG- Measures horizontal and vertical positions and displays (but currently does not measure) torsional eye movements- No major difference in the accuracy of horizontal and vertical eye movements ENG- Measures horizontal and vertical positions but cannot measure or display torsional eye movements- Vertical eye movements are usually noisy and contaminated by eye blinks Practical Implications-VNG can visualize torsional nystagmus....
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VNG-Findings-Treatments - Interpretation of Video...

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