Research and Resources for Fall and Balance Wellness and Prevention
Research
Resources
An In-Home Fall Prevention Checklist for Older Adults: A publication of the National Center for Injury Prevention and Control of the Centers for Disease Control and Prevention (Word document)
Balance Disorders: An Overview
Costs of Falls Among Older Adults A publication of the National Center for Injury Prevention and Control of the Centers for Disease Control and Prevention
Falls Among Older Adults: An Overview Word document
Guideline for the Prevention of Falls in Older Persons. American Geriatric Society, et al
How to Conduct a "Welcome to Medicare” Visit: You and your patient have a lot of ground to cover. Here's one way to get it all done.
JCAHO Nursing Home Compliance 2005 Word document
Medical Management of Vestibular Disorders and Vestibular Rehabilitation
Prevent Painful Falls in Older Persons: Dr Green's Study Results
Reduce Injuries from Falls New England Journal of Medicine
Vibration therapy improves balance in elderly
Inner Ear Balance Disorders Come with Age; Major Cause of Falls by Senior Citizens. Article published by Senior Journal online. Click on the link below to view the article www.SeniorJournal.com/NEWS/Aging/2009/20090526-InnerEarBalance.htm
For a PDF format of this article, click here
VNG: State-of-the-art Clinical Balance Disorder Testing For a text version of this article, click here
Whole body vibration therapy to reduce fall risk in elderly
Resources
International Fall Prevention Institute www.preventfalls.org
The Vestibular Disorders Association (VEDA) is a non-profit organization that serves people with vestibular disorders and the health professionals who treat them www.vestibular.org
Centers for Disease Control "Falls and Hip Fractures Among Older People" www.cdc.gov/HomeandRecreationalSafety/Falls/index.html
Senate Bill 1922, A Bill to expand and intensify research and related activities concerning the elderly and falls (PDF format)
www.nfsi.org/pdfs/sen1922.pdf
"Guideline for the prevention of falls in older persons" released by a joint committee of the American Geriatric Society, British Geriatric Society and the American Academy of Orthopedic Surgeons (PDF format)
www.americangeriatrics.org/products/positionpapers/Falls.pdf
VNG: State-of-the-art Clinical Balance Disorder Testing
While diagnosis of the dizzy patient has been and remains a difficult task: requiring a patient history, physical examination and diagnostic tests; the otoneurologic community is enjoying a recent significant advance in the technology available for eye movement testing. ENG has long been the primary test of the eye movements used for patients with complaints of dizziness or unsteadiness. ENG remains the primary test, but videonystagmyography (VNG) has become more available and robust. Whereas early versions of VNG were awkward to use, had difficulty tracking the eyes of many patients and had analysis algorithms that were untested, most of these problems have been addressed in newer versions. In the majority of vestibular test situations, VNG offers a number of advantages over conventional ENG.
Videonystagmography (VNG) is a method of recording eye movements that uses digital video image technology to determine eye position. This represents a major change from ENG, which relies on the corneo-retinal potential of the eye to determine changes in eye position. By using infra-red illumination, VNG technology can be used to establish eye position during tracking of visible targets (saccade, tracking, gaze and optokinetic tests) as well as in an environment that includes no visible light (for position testing and caloric tests), thereby eliminating fixation targets for the patient.
When using VNG, small cameras mounted in goggles capture images of the eyes. Eye position is established from a digitized image by locating the pupil and tracking its center. Some systems do this with a camera mounted directly in front of the eye. This, however, precludes the use of that eye to view a target. Another approach is to use dichroic filters placed inside the goggles. Dichroic filters are somewhat like two-way mirrors. They reflect infra-red light and allow visible light to pass through them. Cameras mounted outside the line of sight capture a reflected image of the eyes. Because the light from visible targets can pass through the filters, images of the eyes are available as they are viewing these targets. Computer algorithms analyze the individual images of the eyes, which are taken 30 or 60 times per second. Those samples are used to locate the pupil and the pupil's position is passed to the data repository. Once the eye position is established, algorithms work as they do with ENG to plot, measure and analyze the movements of the eye.
Advantages of VNG Technology
VNG technology is easy to use. There is no application of electrodes, no concern about poor connections, bad electrodes or leads. Adjustments are seldom required and calibration is generally easier than with electrodes. Furthermore, only one calibration is necessary, as there is no dependence upon the corneo-retinal potential used for ENG. With ENG, the corneo-retinal potential can change over time, making it necessary to calibrate several times during a battery of tests. Patients generally prefer not having electrodes attached, although some may not like wearing the goggles.
VNG eliminates external electrical noise, biological noise from EMG, EKG and EEG, as well as electrical drift, all of which have become accepted, but annoying aspects of ENG testing. Tracings are amazingly "clean". (Refer to Figure One).
Click on image for an enlarged view.
An advantage of VNG testing is a video image that allows the clinician to view the eye movements, even as the patient is in a completely darkened environment. This provides assurance that the recorded eye movements are consistent with actual eye movements, in order to help to abstract from artifact. Also, it is more convenient to view the eyes on a monitor than to attempt to view the eyes during difficult-to-observe positions; for example, after a Hallpike maneuver. Finally, and perhaps most importantly, the eye movements can be recorded in standard video format (video that can be played back on a video cassette recorder (VCR). This allows careful review of eye movement responses to stimuli and adds the ability to assess torsional movements. Assessment of torsional eye movements is of particular interest in the diagnosis and treatment of benign paroxysmal positional vertigo (BPPV). Proper assessment and treatment is heavily dependent upon knowledge of the torsional eye movement responses to stimuli and the responses to the maneuvers used to treat BPPV. Table One shows some of these responses and their implications.
Click on image for an enlarged view.
Limitations of VNG Technology
VNG cannot be used to test all patients. Patients with certain facial shapes and eye spacings are more difficult to test because the goggles may not fit properly. Some goggles are more flexible than others, but all have limitations to some extent. Some patients have eye characteristics that make them more difficult to test, such as deep-set eyes and eyeliner tattoos. Some patients blink frequently enough that the video images are not useful. Long or heavily made-up eyelashes also cause difficulty.
When conducting tests in which the goggles are open, to allow the patient to see targets such as those on a light bar during a tracking test, bright lights at inappropriate angles can cause reflections that make recording difficult. Reducing ambient light generally solves this problem. VNG uses sampling rates that are marginal for measuring saccadic velocities. While rates of 30 Hz are certainly too slow to measure high speed movements, some systems have tested patients using a 60 Hz sampling rate and achieved velocities that matched those measured with ENG at speeds up to 600 degrees per second.
Summary
Videonystagmograhpy (VNG) can provide highly useful, easily administered testing of eye movements. The tests are permanently recorded, which allows for careful review of eye movement responses to stimuli and adds the ability to assess torsional movements. Furthermore, it can offer incremental information that can prove of significant value to the diagnostic process. The equipment does not require regular calibration, does not depend upon good connections and does not use electrodes. Tracings are amazingly "clean". Videonystagmyography (VNG) has become more available and robust as a result of recent significant advances in the technology available for eye movement testing.
| 
