Neuromodulation: Technology at the Neural Interface (onlinelibrary.wiley.com) DOI: 10.1111/ner.12187
From the Editor in Chief
This supplement to Neuromodulation: Technology at the Neural Interface, produced with a generous unrestricted educational grant from Medtronic Neurological, allows us to delve deeply into one small but clinically important factor in the delivery of spinal cord stimulation for the treatment of intractable pain: the relationship between the stimulating electrode and its neural target and changes that occur in this relationship during patient movement. As the perceived stimulation intensity varies inversely with the square of the distance between electrode and neural target, small changes in this distance can result in significant changes in the strength of stimulation induced paresthesias. While on casual reflection this appears to be a trivial issue, in clinical practice it is sometimes a therapy limiting problem. First, patients may experience rapid and profound variations in perceived signal intensity as they participate in normal activities of daily living. From lying down to sitting to standing up, patients may note a complete loss of stimulation induced paresthesias and, as a result, the return of their pain, while moving in the other direction, analgesic stimulation may quickly become shocking and painful in nature. As one of the goals of therapy is to increase activity, these problems can become worse over time after successful spinal cord stimulation therapy. Secondly, the changes in paresthetic intensity with movement force our patients to attend regularly to that stimulation as well as their pain. In response to changes in the intensity of stimulation induced paresthesias, patients must interact with their programmers to adjust the stimulation so that it remains comfortable and decreases their pain. Not only is this irritating and time consuming, but it is contrary to our other paradigms for optimal control of chronic pain. Pain psychologists have told us for decades that distraction from pain, the ability to focus on other events rather than our pain, helps us to better cope and limit the experience of chronic pain. Standard spinal cord stimulation systems, by requiring con-
tinual patient input, force our patients suffering from chronic pain to do the exact opposite. They must continually attend to their pain and paresthesias to optimize pain relief. This is certainly a suboptimal solution. In this supplement, several international leaders in both the research and clinical practice of spinal cord stimulation weigh in on various aspects of this issue. One of the recently deceased fathers of our field, Dr. Krishna Kumar and co-author Dr. David Caraway, write eloquently about the current clinical challenges of spinal cord stimulation. I have contributed my clinical insights about the differing challenges of spinal cord stimulation relative to the local anatomic environment along the neuraxis from the foramen magnum to the spinal foramena and their potential solutions. Research into the principles of spinal cord activation during epidural spinal cord stimulation is reviewed by Drs. Gabi Molnar and Giancarlo Barolat and while Drs. Timothy Denison and Brian Litt discuss the field of feedback control systems as they apply to neuromodulation and how they might come to bear on the problem of positional changes in spinal cord stimulation. Drs. Christophe Perruchoud, Eric Buchser and Rod Taylor then provide an elegant discussion of activity assessment in the chronic pain patient. The supplement is rounded out with a clinical assessment of improving the patient experience with spinal cord stimulation and the negative implications of position related changes by Drs. Edgar Ross and David Abejon. This is but the first of several such topic focused supplements that are planned for the future of Neuromodulation. It is our hope that they will inspire continued discussion, innovation and advances in our rapidly growing field. Robert M. Levy, MD, PhD. Marcus Neuroscience Institute Boca Raton, FL, USA
1
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 1
From the Editor in Chief
This supplement to Neuromodulation: Technology at the Neural Interface, produced with a generous unrestricted educational grant from Medtronic Neurological, allows us to delve deeply into one small but clinically important factor in the delivery of spinal cord stimulation for the treatment of intractable pain: the relationship between the stimulating electrode and its neural target and changes that occur in this relationship during patient movement. As the perceived stimulation intensity varies inversely with the square of the distance between electrode and neural target, small changes in this distance can result in significant changes in the strength of stimulation induced paresthesias. While on casual reflection this appears to be a trivial issue, in clinical practice it is sometimes a therapy limiting problem. First, patients may experience rapid and profound variations in perceived signal intensity as they participate in normal activities of daily living. From lying down to sitting to standing up, patients may note a complete loss of stimulation induced paresthesias and, as a result, the return of their pain, while moving in the other direction, analgesic stimulation may quickly become shocking and painful in nature. As one of the goals of therapy is to increase activity, these problems can become worse over time after successful spinal cord stimulation therapy. Secondly, the changes in paresthetic intensity with movement force our patients to attend regularly to that stimulation as well as their pain. In response to changes in the intensity of stimulation induced paresthesias, patients must interact with their programmers to adjust the stimulation so that it remains comfortable and decreases their pain. Not only is this irritating and time consuming, but it is contrary to our other paradigms for optimal control of chronic pain. Pain psychologists have told us for decades that distraction from pain, the ability to focus on other events rather than our pain, helps us to better cope and limit the experience of chronic pain. Standard spinal cord stimulation systems, by requiring con-
tinual patient input, force our patients suffering from chronic pain to do the exact opposite. They must continually attend to their pain and paresthesias to optimize pain relief. This is certainly a suboptimal solution. In this supplement, several international leaders in both the research and clinical practice of spinal cord stimulation weigh in on various aspects of this issue. One of the recently deceased fathers of our field, Dr. Krishna Kumar and co-author Dr. David Caraway, write eloquently about the current clinical challenges of spinal cord stimulation. I have contributed my clinical insights about the differing challenges of spinal cord stimulation relative to the local anatomic environment along the neuraxis from the foramen magnum to the spinal foramena and their potential solutions. Research into the principles of spinal cord activation during epidural spinal cord stimulation is reviewed by Drs. Gabi Molnar and Giancarlo Barolat and while Drs. Timothy Denison and Brian Litt discuss the field of feedback control systems as they apply to neuromodulation and how they might come to bear on the problem of positional changes in spinal cord stimulation. Drs. Christophe Perruchoud, Eric Buchser and Rod Taylor then provide an elegant discussion of activity assessment in the chronic pain patient. The supplement is rounded out with a clinical assessment of improving the patient experience with spinal cord stimulation and the negative implications of position related changes by Drs. Edgar Ross and David Abejon. This is but the first of several such topic focused supplements that are planned for the future of Neuromodulation. It is our hope that they will inspire continued discussion, innovation and advances in our rapidly growing field. Robert M. Levy, MD, PhD. Marcus Neuroscience Institute Boca Raton, FL, USA
1
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 1
