A videonystagmography (VNG) test evaluates balance by recording eye movements. This procedure helps healthcare providers understand why someone experiences dizziness, vertigo, or other balance issues. Understanding a “positive” VNG test result provides clarity about vestibular health and its implications.
Understanding the VNG Test
The VNG test assesses the vestibular system, including parts of the inner ear and brain that regulate balance and spatial orientation. It relies on the principle that the eyes and inner ears work closely to maintain equilibrium. During the test, special goggles with infrared cameras record involuntary eye movements, known as nystagmus, that occur in response to various stimuli.
Patients typically undergo a VNG test if they experience symptoms such as dizziness, vertigo, lightheadedness, or balance problems. The test objectively measures how the inner ear and brain coordinate stability, providing insights into the underlying cause of these symptoms by analyzing recorded eye movements.
Interpreting a Positive Result
A “positive” VNG test result indicates an abnormality or dysfunction within the vestibular system or its neural pathways. This means recorded eye movements deviated from expected normal responses during specific test components. The VNG test includes three main parts: ocular-motor testing, positional testing, and caloric testing, each providing distinct information.
Abnormal eye movements, particularly nystagmus, are indicators. Nystagmus is rhythmic, repetitive, and uncontrolled eye movement that can occur horizontally, vertically, or in a circular pattern. For instance, during ocular-motor tests, if eyes cannot smoothly track a moving target or exhibit irregular rapid eye movements (saccades), it may suggest central nervous system issues. Positional tests involve moving the head and body into different positions to see if certain movements induce nystagmus, which can indicate inner ear problems, such as displaced particles.
The caloric test assesses each inner ear separately by introducing warm or cool air or water into the ear canal. A significant difference in eye movement response between the two ears (often greater than 20-25%) can point to weakness in one inner ear, suggesting a peripheral vestibular dysfunction. While some nystagmus during positional testing is normal, persistent or direction-changing nystagmus, or nystagmus without head movement, signals an abnormality. The specific patterns of nystagmus and responses across these sub-tests help differentiate between a peripheral issue (originating in the inner ear) and a central issue (involving the brain or central nervous system).
Conditions Indicated by a Positive VNG
A positive VNG result can help identify several conditions affecting balance. Benign Paroxysmal Positional Vertigo (BPPV) is a common cause of vertigo often identified by VNG, showing brief nystagmus episodes triggered by specific head movements, such as during the Dix-Hallpike maneuver. This occurs when tiny calcium crystals dislodge in the inner ear.
Meniere’s disease, a chronic inner ear disorder, can also be indicated by VNG, often presenting with symptoms like vertigo, hearing loss, and ringing in the ears. VNG findings in Meniere’s disease may include unilateral weakness in caloric responses or positional nystagmus. Vestibular neuritis or labyrinthitis, inflammations of the inner ear or its nerve, are frequently diagnosed with VNG due to a characteristic unilateral weakness in the caloric test.
In some instances, VNG results may point to a more central (brain-related) issue rather than an inner ear problem. Abnormalities in ocular-motor tests, such as difficulty with smooth pursuit or saccades, can suggest central nervous system disorders like multiple sclerosis, stroke, or brain tumors. While VNG does not directly diagnose these central conditions, it can reveal signs that warrant further neurological evaluation.
Next Steps After a Positive Result
After a positive VNG test, a healthcare provider (often an audiologist, otolaryngologist, or neurologist) will discuss the results in detail. The VNG test provides valuable information, forming part of a broader diagnostic process. The results help guide the specialist in understanding the nature and location of the balance disorder.
Based on VNG findings, additional diagnostic tests may be recommended to confirm or refine the diagnosis. These can include imaging studies like an MRI to rule out structural issues in the brain or inner ear, or other audiology tests to assess hearing function. The information gathered from the VNG and any subsequent tests will inform the development of a personalized treatment plan. This plan might involve vestibular rehabilitation therapy, medication to manage symptoms, or lifestyle adjustments aimed at improving balance and reducing dizziness.