videonystagmography

Videonystagmography (VNG) is a diagnostic test that assesses the function of the vestibular system and ocular motor control by recording eye movements with infrared video goggles. The test provides objective measures of nystagmus, gaze-holding, smooth pursuit, saccades, and optokinetic responses, helping to differentiate peripheral vestibular disorders from central causes of dizziness.

The VNG procedure typically includes calibration followed by a series of tasks. Patients wear lightweight goggles that track eye movements while they perform aging-neutral tasks such as gaze fixation, looking to targets of various distances, and tracking moving objects. Additional components often involve free or gaze-evoked nystagmus assessment, positional testing, and caloric testing. Caloric testing uses warm and cool air or water delivered to each ear to induce endolymphatic currents and provoke nystagmus, revealing unilateral vestibular weakness or canal paresis.

Interpretation relies on the pattern of eye movements across tests. Spontaneous or gaze-evoked nystagmus with reduced responses to calorics on one side suggests unilateral vestibular hypofunction. Bilateral hypofunction may show diminished responses to both ears. Central vestibular disorders may produce vertical or direction-changing nystagmus and abnormalities in pursuit or saccade tasks, sometimes with preserved caloric responses. Results are integrated with clinical history and other tests to guide diagnosis and management.

VNG offers objective, noninvasive data that can aid in diagnosing vestibular neuritis, Meniere’s disease, vestibular schwannoma, migrainous vertigo, and other balance disorders. Limitations include reliance on patient cooperation and the potential discomfort from caloric testing, along with variability in technique and interpretation across settings.