VNG/ENG Testing

Dizziness is a common complaint but challenging to evaluate due to its complexity, subjectivity, and broad differential. Following a comprehensive history and physical examination, dizziness can often be attributed to the peripheral vestibular system, central nervous system, or cardiovascular system. When a peripheral vestibular etiology of dizziness is suspected, videonystagmography (VNG) or electronystagmography (ENG) can be performed to evaluate the dizziness further. VNG/ENG measures nystagmus, which are rhythmic, rapid eye movements with a slow and fast phase, to provide objective information about the peripheral vestibular system. Nystagmus is named for its fast phase and is described by its rotary, vertical, or horizontal directionality. Peripheral vestibular system abnormalities lead to an asymmetry that disturbs the vestibulo-ocular reflex (VOR) pathway, resulting in nystagmus.  ENG is one of the oldest methods employed in detecting and evaluating abnormal eye movements in a dizzy patient and utilizes electrodes placed above and below the eyes and on the temples to track corneal-retinal potentials recorded with a polygraph tracer. The most significant advantage of ENG over VNG is its efficacy in patients who cannot open their eyes or have significant visual impairment. However, ENG cannot measure rotational or torsional nystagmus and may be negatively impacted by retinal pathology. In current clinical practice, VNG has largely replaced ENG. VNG utilizes magnifying goggles with a computerized tracer to track the center of the pupil; eye movements may be video-recorded during testing. VNG offers increased reliability compared to ENG and can better recognize torsional and subtle nystagmus. However, certain patients, including young children, may be intolerant of the magnifying goggles.