Videonystagmography (VNG) is a specialized diagnostic test designed to assess the function of the vestibular system, which plays a role in maintaining balance and spatial orientation. This non-invasive procedure utilizes advanced video technology to record and analyze eye movements. The primary purpose of a VNG is to help healthcare providers identify the underlying causes of dizziness, vertigo, and other balance-related issues.
What VNG Measures
VNG specifically measures nystagmus, which refers to involuntary, repetitive eye movements that can occur vertically, horizontally, or in a rotational pattern. These uncontrolled eye movements often indicate a problem within the vestibular system, which includes parts of the inner ear and brain pathways that coordinate balance. By observing and quantifying these movements, VNG provides insights into how well the inner ear and brain are working together to maintain equilibrium.
Reasons for the Test
Doctors often recommend a VNG test when patients experience symptoms such as persistent dizziness, vertigo (a sensation of spinning), or unsteadiness. These symptoms can arise from various conditions affecting the inner ear, such as Benign Paroxysmal Positional Vertigo (BPPV), Meniere’s disease, or vestibular neuritis. The test also helps identify potential issues related to neurological conditions, aiding in localizing the source of the problem. By thoroughly evaluating eye movements, VNG helps differentiate between inner ear disorders and those originating in the brain.
What to Expect During the Test
Before the VNG test, patients are advised to avoid certain medications, caffeine, and alcohol for at least 24 hours. It is also recommended to wear comfortable clothing and refrain from wearing eye makeup. During the procedure, you will sit in a darkened room and wear lightweight goggles equipped with infrared cameras that record your eye movements. The entire procedure does not cause pain.
The VNG test involves several sub-tests designed to assess different aspects of your balance system.
Oculomotor Testing
This part requires you to follow moving lights or targets on a screen with your eyes while keeping your head still.
Positional Testing
This involves a healthcare provider gently moving your head and body into different positions, such as lying back or sitting up, to observe any resulting nystagmus.
Caloric Testing
Small bursts of warm and cool air or water are introduced into each ear canal to stimulate the inner ear and assess its responsiveness. This stimulation temporarily induces nystagmus for analysis.
Understanding Your Results
After the VNG test, a specialist will interpret the recorded eye movement patterns. The presence, direction, and intensity of nystagmus during different parts of the test provide clues about the nature and location of any vestibular dysfunction. For example, specific patterns of nystagmus observed during positional testing might indicate BPPV, while responses during caloric testing can help determine if one inner ear is functioning differently than the other.
The VNG results contribute to a comprehensive diagnosis. It helps distinguish between peripheral vestibular disorders, which affect the inner ear, and central vestibular disorders, which involve the brain. Based on the findings, the healthcare provider will discuss what the results mean, which may involve recommending further diagnostic tests, developing a personalized treatment plan, or referring you to another specialist for continued care.