Videonystagmography (VNG)
Videonystagmography
(VNG) is a series of tests used to determine the causes of a patient's dizziness
or balance disorders. If dizziness is not caused by the vestibular portion of
the inner ear, it might be caused by the brain, by medical disorders such as
low blood pressure, or by psychological problems such as anxiety. VNG is a test
used to determine whether or not dizziness may be due to inner ear disease.Dizziness: Lightheadedness or Vertigo?
Dizziness is often used to describe either lightheadedness or vertigo, so it is important to know the difference in symptoms to help narrow down the list of possible problems.Vertigo: the illusion that you or your surroundings are moving (spinning, leaning, falling) without actual movement. Severe vertigo can cause nausea and even lead to vomiting. Physically you may lose your balance or have trouble walking. Vertigo is not the same as motion sickness because no repeated motion is triggering the feeling.
Lightheadedness is the sensation of almost fainting or passing out, but without the feeling your surroundings are moving. Lightheadedness often disappears while lying down. When lightheadedness gets worse it can feel like almost fainting and may sometimes feel nauseating to the point of vomiting. It is not uncommon to sometimes feel lightheaded and it is usually is not caused by a serious problem, i.e. it could be a momentary drop in blood pressure from getting up too quickly from being seated or lying down.
How does VNG Work?
VNG is a complete diagnostic system for recording, analyzing and reporting involuntary eye movements, called nystagmus, using video imaging technology. Hi-tech video goggles with infrared cameras are worn while you look or lie in different positions.There are four main parts to the VNG. The saccade test evaluates rapid eye movements. The tracking test evaluates movement of the eyes as they follow a visual target. The positional test measures dizziness associated with positions of the head. The caloric test measures responses to warm and cold water circulated through a small, soft tube in the ear canal. The cameras record the eye movements and display then on a video/computer screen. This allows the examiner to see how the eyes move which is very helpful in assessing balance system health
About BPPV
In Benign Paroxysmal Positional Vertigo (BPPV) dizziness is generally thought to be due to debris which has collected within a part of the inner ear. This debris can be thought of as "ear rocks", although the formal name is "otoconia". Ear rocks are small crystals of calcium carbonate derived from a structure in the ear called the "utricle" (figure1 ). While the saccule also contains otoconia, they are not able to migrate into the canal system. The utricle may have been damaged by head injury, infection, or other disorder of the inner ear, or may have degenerated because of advanced age. Normally otoconia appear to have a slow turnover. They are probably dissolved naturally as well as actively reabsorbed by the "dark cells" of the labyrinth (Lim, 1973, 1984), which are found adjacent to the utricle and the crista, although this idea is not accepted by all (see Zucca, 1998, and Buckingham, 1999).BPPV is a common cause of dizziness. About 20% of all dizziness is due to BPPV. While BPPV can occur in children (Uneri and Turkdogan, 2003), the older you are, the more likely it is that your dizziness is due to BPPV. About 50% of all dizziness in older people is due to BPPV. In a recent study, 9% of a group of urban dwelling elders were found to have undiagnosed BPPV (Oghalai et al., 2000).
The symptoms of BPPV include dizziness or vertigo, lightheadedness, imbalance, and nausea. Activities which bring on symptoms will vary among persons, but symptoms are almost always precipitated by a change of position of the head with respect to gravity. Getting out of bed or rolling over in bed are common "problem" motions . Because people with BPPV often feel dizzy and unsteady when they tip their heads back to look up, sometimes BPPV is called "top shelf vertigo." Women with BPPV may find that the use of shampoo bowls in beauty parlors brings on symptoms. An intermittent pattern is common. BPPV may be present for a few weeks, then stop, then come back again.