What is computerized dynamic posturography (CDP)?
Computerized dynamic posturography (CDP) is a scientific framework for understanding the control of balance and postural stability. CDP can objectively quantify functional impairments and is ideal for physical therapy and rehabilitation exercises. It utilizes a force plate to measure the center of pressure in the anterior‑posterior and lateral directions. The center of gravity and the patient sway are estimated from the center of pressure.
To further grasp the concept of CDP, we spoke with its inventor, Lewis M. Nashner, Sc.D. His career started in the quite different, but in some ways related, field of aeronautical engineering. Continue reading to hear his story and to learn the benefits of CDP.
Could you describe your time at MIT?
I began my graduate education at MIT as an aeronautical engineer. At that time, MIT was involved with research directed at the upcoming NASA lunar landing. As a member of the laboratory researching control systems to assist astronauts in the lunar landing, I became very interested in the human balance and vestibular systems. Both systems would be critical components of the landing process to be conducted under zero gravity conditions.
Did you pursue your interest in the human balance and vestibular systems?
After graduating with a doctorate degree combining systems engineering and human neurophysiology, I joined the Neurological Sciences Institute, part of the Oregon Health and Sciences University in Portland, Oregon. I conducted research into human movement and balance for 16 years as an NIH funded researcher.
While collaborating with a research neurotologist, Owen Black, and a neurologist, Bob Grimm, we became interested in the potential for evaluating balance and movement disorder patients with my laboratory dynamic posturography technology. Then, when Ann Shumway Cook and Fay Horak joined my laboratory as post-doctoral fellows, we became further interested in using the technology for retraining the balance system.
How did this lead to NeuroCom Inc. and CDP?
With startup funding from the NIH, I left my research laboratory to the direction of Fay Horak and founded NeuroCom Inc. to develop, manufacture, and market a CDP system based on the research of my colleagues and me. After 25 years of educating the medical community, CDP became a clinical standard for balance evaluation and training. At this point, NeuroCom was sold to a larger medical device company.
What are the benefits of CDP?
The balance system involves complex, adaptive interactions among a variety of sensory and motor components. When pathology strikes one of these components, the balance system attempts to adapt by changing how other components behave. This adaptive process can be even more difficult to untangle when several components are impaired in older patients.
Thus, by the time a patient sees a medical professional for a balance problem, attempting to localize the pathology can be difficult or impossible. Even when a pathology is identified, the symptoms and impairments can vary widely. The greatest value of CDP is to quantify how the patient is using their balance senses under a variety of conditions. With or without information about underlying pathology, medical professionals can use the CDP results to design a balance training program and then track the results.
Why use VR together with CDP?
Vision is a powerful input to the balance system. To most effectively test the role played by vision, it is necessary to expose the patient to as wide a variety of visual conditions relevant to daily life functions as possible. With the tremendous advances in computer graphics technology, VR is now the best practical method for achieving this goal.
With VR, the clinician can change properties of the visual scene to reduce or enhance object ‘clutter’, positions of nearer and farther objects, colors, and contrast. All properties that influence motion perceptions within the visual environment. Also, the visual scene can be programmed to either move in response to the patient or randomly.
All these capabilities can be of value when the patient is evaluated and trained.
About Dr. Lewis M. Nashner
Dr. Lewis M. Nashner holds a BSc in Aerospace, Aeronautical and Astronautical Engineering, having graduated from the Massachusetts Institute of Technology (MIT) in 1965. Dr. Nashner went on to research human movement and balance and earned an Sc.D. in Biomedical/Medical Engineering in 1970, also from MIT. His extensive career includes a role as Chairman and Senior Scientist at the Neurological Sciences Institute. Dr. Nashner was also the CEO and Founder of NeuroCom Inc., where he developed the first CDP system.
