Nystagmography

What it is

Nystagmography is a diagnostic test battery that measures eye movements in response to vestibular and visual stimuli. The vestibular system provides the brain with information about our motion and positioning. Vestibular information is integrated with sensory input from the visual and somatosensory systems in order to stabilize our gaze, head, and trunk, and coordinate the movements of the lower body to maintain balance. The responses of the eyes are measured and interpreted to diagnose the causes of vertigo, dizziness, and balance problems.

Based on the technology used to record the eye movements, it is called either:

Electronystagmography (ENG), OR
Videonystagmography (VNG).

How it works

With electronystagmography, the test is performed by attaching electrodes around the eye and measuring the movements of the eye in relation to the ground electrode. With videonystagmography, infrared video systems are used to detect the eye movements, allowing for a more detailed observation of those movements.

The standard nystagmographic test battery consists of 3 parts:

oculomotor evaluation (spontaneous nystagmus, saccades, pursuit and gaze testing, optokinetic)
positioning/positional testing
caloric stimulation of the vestibular system

The comparison of results obtained from various nystagmographic sub-tests assists in determining whether a disorder is central or peripheral. In peripheral vestibular disorders, the side of lesion can be inferred from the results of caloric stimulation and, to some degree, from positional findings.

While nystagmography is the most widely used clinical laboratory test to assess vestibular function, normal test results do not necessarily mean that a patient has typical vestibular function. A clinical history and otologic examination are also vital in formulating a diagnosis and treatment plan for a patient presenting with dizziness or vertigo.