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Impedance Neurography: A Novel Nerve Imaging Technology

By: , Posted on: October 9, 2017

finding the nerve

Pain management is an area of medical practice that is both fascinating and frustrating. The fascination derives from being presented with diagnostic conundrums which can also be frustrating in part due to a lack of tools for the clinician. Often, when all of the traditional imaging studies are ‘normal’ the diagnosis depends on the ability to perform diagnostic maneuvers, such as nerve blocks, to demonstrate the site of pathology. When practitioners lacking the skills for such diagnostic techniques attempt to evaluate pain, all too often diagnoses of convenience, e.g., conversion reaction, are inappropriately applied and acted upon.

Since not all practitioners are going to become expert in the performance of difficult regional anesthesia techniques, what would be very helpful would be the availability of a nerve-specific imaging technology that was not limited by nerve size, depth, or state of function. A fortuitous observation from the late 1980s has led to the development of just such a technology.

The observation that nerves could be detected at the skin surface by the use of a TENS unit was the start of this process. The best part of these early studies was that it was entirely sensationless for the patient, though not for the clinician! It was obviously working through some mechanism that did not involve electrically firing the patient’s nerves. Over 25 years of study, the underlying mechanism has been outlined and found to involve a new understanding of the biophysics of the neuronal cell membrane and its response to applied electrical fields. Alterations of the neuronal cell membrane due to injury or neuropathic states, e.g., diabetes, can be detected using this technology making it much more than a simple location technology; it also provides state of function information.

Considering that many, chronically painful conditions begin with peripheral injury, a technology with the capability to evaluate the peripheral nerve state of function would be most helpful. At present these assessments must be inferred from measuring nerve conduction characteristics or the activation of muscles by nerves. And while we have remarkable tools for evaluating the state of function of the central nervous system, there exist few techniques for similarly assessing the periphery. The development of Impedance Neurography changes this situation and represents a step forward in pain assessment and management. At the same time, insights regarding the neuronal cell membrane electrical responses that derive from this new technology will be quite helpful in improved neuromodulation technologies.

Finding the Nerve: The Story of Impedence Neuorgraphy

Finding the Nerve: The Story of Impedence Neurography

Philip Cory is the author of the book Finding the Nerve: The Story of Impedence Neuorgraphy that discusses research that elucidates the nature of nerve simulation via externally applied electrical fields, and how it has led to an entirely new understanding of neuronal cell membrane biophysics and defined a novel nerve imaging technology. It is scheduled for publication in early October.

To order a print or ecopy of the book, visit the Elsevier Store. Apply discount code STC317 at check out and receive up to 30% off the list price and free global shipping.

About the Author:

Philip Cory completed an Anesthesiology residency and fellowship at Virginia Mason Hospital after receiving his M.D. from the University of Washington School of Medicine, and his BA in chemistry from Whitworth College. His observation of iatrogenic respiratory failure following intercostal block, led to his fellowship research in the role of chest wall paralysis in alterations of pulmonary mechanics. His main area of interest in pain management came from work at the University of Washington Department of Anesthesiology Chronic Pain Management Clinic in the 1970s when that facility was in the forefront of investigating the pathophysiology of pain. It was a heady time for a young physician to be involved in helping to sort out and manage difficult medical problems for patients while working with mentors who were leaders in the field of pain management.

It was during the time he was on faculty at The Milton S. Hershey Medical Center of Penn State University that he noticed some intriguing observations related to the ability to detect the position of myofascial trigger points using a TENS unit. After leaving Penn State for private practice in Bozeman, MT, he began work to develop instrumentation to both document and study the TENS unit observations. This work was accomplished during ‘free’ time, which is scarce for a busy anesthesiologist clinician, often on call every third night in those days. The situation was not helped by the fact that the observations, though very reproducible, were not discussed in the medical literature and there was no known basis for them. Over 25 years of research, he produced a body of evidence supporting the legitimacy of the effects, and constructed a coherent hypothesis explaining the mechanism behind the observations. After retirement, he continues to study some of the implications of the research and now holds 8 patents with additional provisional patents filed. During the years of his research efforts, no publications outside of the patent literature were produced and it is now appropriate that documentation of these efforts be published in book format where you can discover the adventure of how the process began and where it has led.

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