Focal hand dystonia (FHd) is a subject of great interest to me. Of the common musculoskeletal and neuromuscular movement disorders affecting the hand, FHd probably has the lowest prevalence, but may be one of the most disabling. Stressful, repetitive use of the hand can have a significant effect on the etiology and incidence of hand dystonia. The sudden onset of hand dystonia can have a catastrophic impact, especially for performing artists, writers or professionals heavily engaged in writing, computer drawing, software programming, and data entry.1
Over the years, the diagnosis of FHd has been somewhat evasive. We neither fully understand the etiology nor the treatment of patients with FHd. Historically, for many years, hand dystonia was classified as a psychological rather than a neurological disorder. As scientists unraveled more about the etiology and the treatment of FHd, it has become increasingly clear, hand specialists in medicine and rehabilitation have an important role to play in terms of discovery, prevention, and recovery of function.2, 3, 4, 5, 6
Occupational-related hand dystonia most commonly develops in talented and successful individuals. The problem can develop slowly or suddenly. It begins as an annoying, yet painless, clumsiness of the hand. Initially, in response to the in-coordination, the patient responds by working longer hours and practicing harder to make the hand work more precisely. The more intense the practice, the worse the problem seems to get. Historically, individuals with occupational hand cramps pursue a long search for an explanation before they see a physician who makes the diagnosis. Many patients search even longer and broader to find the best treatment. Ultimately, the patient learns that he or she must assume a primary responsibility toward recovery.
Leon Fleischer, Gary Graffman, Robert Shuman, and David Leisner are four very well-known musicians who have openly discussed their hand dystonia. In the past, musicians faced with this problem had to end their performance career. Although today, the public and the Health care community are more aware of this condition, the road to recovery is neither easy nor smooth. Self-determination, the ability to stop the abnormal, involuntary movements, and the commitment to pursue retraining the brain are probably the most important characteristics of the patient who recovers. Traditional and complementary therapies are usually paired with rehabilitation techniques directed toward neural adaptation to restore the functional use of the hand.
David Leisner (www.davidleisner.com/FocalDystonia.html) speaks freely about his full recovery. For over ten years, he looked for help and tried many different interventions, none with any success. Some intervention strategies even made him worse. Ultimately, he not only had to modify his performance techniques, but also changed his life style, his work, his commitment to fitness, his recreation, and some of the characteristics of his personality. Once David realized only he could change his situation, the process of recovery took about a year. When David told me his story, I was impressed with his insight and the meticulous and careful procedures he developed to improve sensorimotor processing. Basically, he successfully retrained his brain.
I first became interested in the problem of hand dystonia in 1988, when I assumed the role as the physical therapy consultant for the Peter Ostwald Program for Performing Artists at the University of California, San Francisco (UCSF). One of my first consultations was with a pianist with musician's cramp. Many of the physicians consulting in the program were not only talented medical practitioners, but also were performing artists. Our team was knowledgeable, supportive, and sensitive to the issues presented by our patients. However, even with our best efforts, we were not very successful in guiding the recovery of our patients with focal dystonia, especially when a patient had a long history of severe hand. Interestingly, there was something compelling about the history that caught our attention: the long hours of practice that had led to a unique and successful performance career seemed to be associated with the development of the dystonia. This common circumstance led us to hypothesize that the condition might represent a case of aberrant learning.
At this time, there was a paradigm shift taking place in neuroscience. Up until the 80s, the assumption was that the central nervous system only made profound changes during development. However, Michael Merzenich, PhD and others began to report remarkable changes in the central nervous system driven by specific, goal-directed, repetitive activities progressed in difficulty.7 With many animal studies carried out in multiple laboratories across the country, reinforced with preliminary clinical trials, researchers ultimately reported it was possible to drive changes in the central nervous system across the lifespan. These changes collectively accounted for new skill development, skill refinement achieved with practice, and a slowing of the aging process.
Within the context of these exciting new findings about adaptive brain plasticity processes, Dr. Frank Wilson, MD, neurologist and past Medical Director for the UCSF Peter Ostwald Health Program for Performing Artists, and I decided to pursue our question about the possibility of abnormal learning and neural adaptation as one etiological factor contributing to the origin of FHd. We arranged a meeting with Dr. Michael Merzenich, PhD. We wanted to discuss our observations and hear his thoughts about our proposed theoretical construct. In 1991, I took a sabbatical to work in the neuroscience laboratory with Dr. Merzenich. Our objective was to create a primate model of dystonia. My son, a graduate student in mechanical engineering at the time, crafted the instrumentation I needed for training. My challenge was to learn to the skills necessary to carry out primate research. Then I had to learn to socialize the primates to the training cage and ultimately train them to perform the repetitive task. I also had to encourage the primate to become “obsessive” about squeezing the hand-piece. The next step was to recruit a surgeon, learn to become an anesthesiologist, a pharmacologist, and an electrophysiologist. Finally, I had to complete the team to be able to map around the clock for five days. I was fortunate to have David Blake, PhD, Srikantan Nagarajan, PhD, Purvis Bedenbaugh, PhD, and Stephen Cheung, MD who helped me with this research. The training and ultimately the cortical mapping was challenging and time demanding for everyone.
We hypothesized if an animal would rapidly and stereotypically squeeze the hand-piece thousands of times a day, a breakdown in sensory and motor representation of the hand would likely occur. If the degradation in representation was sufficiently severe, it would lead to a problem in motor control. Because we knew that the brain could change with attended practice, we assumed we would be able to measure cortical reorganization with excessive practice.8
Indeed, we were successful in training primates to perform a simple repetitive task. Some performed the task repetitively enough they developed involuntary patterns of movement dysfunction that appeared to be dystonia. We were excited to present our findings. However, changing a paradigm of thinking is difficult. When we initially reported our results that excessive repetition could lead to FHd, many scientists questioned our animal model of dystonia. Even with the videotape documentation of the movement dysfunction, some researchers and clinicians still did not agree the abnormal movement was dystonia. However, the cortical reorganization of the somatosensory cortex was massive in the monkeys which developed the movement dysfunction. We interpreted our findings as a support for our hypothesis—high levels of repetitive, stereotypical, and near-simultaneous movements can degrade the representation of the digits of the hand. The large, overlapping receptive fields made it impossible for the animals to organize the central nervous system to control the individual digits. We extensively mapped the somatosensory cortex. However, we also documented changes in the sensorimotor cortex and the thalamus.
Our experimental model of hand dystonia was created in Nancimae Owl monkeys. These primates had served as the model for studying brain plasticity for more than ten years. There were no known genetic or familial history of FHd in these primates. Yet after training, we measured extensive reorganization of the somatosensory cortex not only on the hemisphere contralateral to the trained hand, but also in the ipsilateral hemisphere. We concluded that there was a significant and powerful spread of the reorganization because of the intensive training.
I reported out research findings as part of a panel presenting to a large audience of neuroscientists at the Society of Neuroscience. Our perspective was considered innovative but only supported with initial preliminary data. After the conference, Mark Hallett, MD, Division of Neurological Diseases, National Institutes of Health, told some reporters covering our presentation that he would pursue studies to determine if my research findings could be replicated. In addition, Frederick Lenz, MD, Professor, Department of Neuroscience at Johns Hopkins University,9 invited me to participate in the analysis of his neurophysiological data comparing the somatosensory representation of the hand in patients undergoing surgery for severe tremor and those undergoing surgery for severe generalized dystonia. We found abnormal somatosensory representations of the hand only in the patients with dystonia.9
Not too long after this report, I had the opportunity to meet Mary Barbe, PhD and Ann Barr, PhD, PT from Temple University. These researchers were studying the physiological effects of repetition in a rat model. They not only documented local inflammatory changes related to repetitive movements, but also clearly noted a spread of these physiological changes to the untrained limb and ultimately in the central nervous system. I had the opportunity to observe the rats picking up pellets from a feeding tube after long hours of intense repetitive training. Drs. Barbe and Barr had noted a decrease in the quality of movement of their animals, however, when I suggested this might be “focal dystonia,” we decided to pursue a collaboration with Drs. Merzenich, Olivier Coq, and Fabrizzio Strazzo in the UCSF Keck Center for Neuroscience. Dr. Barbe brought her trained rats to San Francisco and together the team performed blinded somatosensory and motor mapping of controls and trained rats. Our findings were consistent with the primate studies.8, 10
Today, neuroimaging studies are performed on patients who already have hand dystonia. One interpretation of the degradation of the representation on the ipsilateral cortex of the trained hand is that there were pre-existing anomalies in the hand representation before the development of the dystonia. These pre-existing changes in representation have been interpreted as a risk factor for development of hand dystonia rather than as a consequence of the dystonia. To confirm the cause/effect relationship of these abnormal findings in the ipsilateral cortex, it would be necessary to carry out longitudinal studies of individuals in professions characterized by long hours of repetitive hand movements. These individuals would need to enroll in the study well before developing any signs of dystonia. We know to become a performing artist or a skilled athlete, long hours of focused practice are necessary. Furthermore, for most individuals, this practice is associated with high levels of exquisite performance, not dystonia.
I think it is clear, all individuals who practice with heavy schedules of repetition (e.g., musicians, writers, lawyers, and keyboarders), do not in fact develop hand dystonia. In our animal models, not all of the rats nor all of the primates developed a dystonia either. Only the compulsive animals, driven to perform the repetitive task with high levels of repetition developed a motor control problem. The animals who worked slowly, took frequent breaks, and performed low levels of repetition did not develop dystonia.11 These findings led to a series of studies by us and others, broadening the insight into the etiology and pathophysiology of FHd that is summarized in this issue.8, 12
Most recently, researchers report objective signs of excessive cortical plasticity in patients with focal dystonia.13, 14, 15 Interestingly, plasticity is generally considered an asset when retraining the brain postinjury. Thus, this unusual sensitivity for neural adaptation may provide the opportunity for individuals to develop exceptionally good fine motor skills both in terms of efficiency and quality. On the other hand, excessive plasticity may be a liability when an individual continues to perform this skill with high levels of near-simultaneous, stereotypical repetition. It is possible that the intense, goal-oriented repetitions required to both maintain and improve performance (e.g., in musicians, keyboarders, computer programmers, assembly line workers, writers), leads to excessive plasticity that ultimately degrades the representation of the hand until involuntary movements replace the desired fine motor movements. This appears to be the case in patients who develop occupational hand cramps.
Over the last 13 years, research on the etiology of focal dystonia has accelerated, both in the basic and clinical sciences.12, 16, 17, 18 Today, a large number of different genes have been identified in patients and their families who develop focal and generalized dystonia. However, everyone with a gene for dystonia, does not develop the condition. Rather, the individual with the genotype for dystonia only develops the phenotype in the face of other environmental, behavioral, pharmacologic, or psychological conditions (e.g., trauma, stress, overuse, and personality characteristics, such as phobias and perseveration).
Clinical experts have been trying to develop universal terminology to more consistently classify the different movement disorders. Dystonia is defined as end-range posturing created by overexcitation and inadequate inhibition. This imbalance leads to involuntary co-contractions of agonists and antagonists. The disorder is usually painless. Most patients have a sensory trick to temporarily quiet the involuntary movements. In occupational hand dystonia, the abnormal movements are only observed during the performance of a target task.19 In other functional activities, the hand performs entirely normally. Furthermore, the dystonic posturing is usually not present during sleep and there is no “catch” when the involved joint is passively moved at different speeds. There may also be some underlying dysfunction in sensory discrimination.20, 21, 22, 23, 24
At this time, neither pharmaceutical and surgical nor behavioral training strategies can assure that each patient with FHd will achieve 100% recovery.25 Research continues to discover more about etiology and effective treatment. Physical and occupational therapists with a special interest in the hand have the opportunity to contribute to the development of new treatment paradigms. Therapists should partner with basic and clinical scientists to study the effectiveness of novel, effective, behavioral exercise interventions to enhance inhibition, quiet excessive excitation, improve cortical organization, and facilitate a balance in sensorimotor integration.
In this special issue on FHd, you will learn about the current theoretical and clinical practice issues for the diagnosis and treatment of this challenging condition of hand dystonia. I feel fortunate that many of the researchers and clinicians I have met over the years have been willing to contribute to this special issue for the Journal of Hand Therapy. This issue should serve as a platform to engage those with a special interest in the hand to continue the discovery regarding the etiology and the management of this condition.
A succinct, insightful overview of the etiology of FHd is provided by Peter Lin, MD and Mark Hallett, MD from the National Institutes of Health, Division of Neurological Disorders. Dr. Goldman, PhD, OTR, CHT discusses the challenge of discriminating fasciculations and muscle cramps from dystonia. Through current paradigms of neuroimaging, Dr. Hinkley, PhD, Rebecca Webster, MSPT, PT and Dr. Srikantan, PhD highlight what we have learned about brain reorganization and dystonia using electrophysiological and magnetic neuroimaging techniques. Stephen Frucht, MD discusses the history, diagnosis, and medical management of patients with focal dystonia, emphasizing the potential benefit of precise and exact injections of botulinum toxin.
Drs. Eckhart Altenmueller, MD and Hans Jabusch, PhD provide insight regarding the psychological characteristics of musicians who develop FHd and how these musicians differ from those who are healthy or those with chronic repetitive strain injuries that lead to musculoskeletal pain rather than dystonia. Dr. Bauer, PhD shares the success of retraining patients with writer's cramp using computer-based biofeedback techniques. Dr. Alison McKenzie, PhD, PT and I share our results on the effect of learning-based sensorimotor training. Drs. Cogiamanian, MD and Priori, MD elaborate on the theme of neuroplasticity and suggest some novel approaches to retraining including immobilization, fatigue, and magnetic stimulation.
In summary, individuals performing jobs requiring rapid, repetitive, near stereotypical movements of the hand, should be educated and trained about stress management, safe biomechanical hand strategies, fitness and wellness, regular timed breaks and the integration of sensory discrimination and quality neuromotor strategies into practice activities designed to improve performance. If involuntary movements begin to interfere with performance, it is best to stop the repetition of these abnormal movements and pursue consultation with teachers and health professionals familiar with occupational hand dystonia. Medications for depression or performance anxiety and injections of botulinum toxin may be helpful in the management of hand dystonia, but it may be critical to pair these medication strategies with disciplined retraining of the brain to facilitate recovery. Neurologists and hand surgeons are critical team coordinators. Physical and occupational therapists bring the unique understanding of exercise to the team. Music teachers can also make important contributions to helping patients modify their playing techniques. I hope everyone who reads this issue will not only have a better understanding about how to evaluate a patient with FHd, but will also have the foundation of knowledge, the logic of inquiry, and the sensitivity to the patient to think outside the box and continue to innovate effective intervention strategies.
FULL TEXT
