Musicians don’t talk much about focal dystonia; perhaps it’s a superstitious avoidance akin to trying to ward off the Evil Eye. For dystonia really is a horror show; arguably the leading career-killing disorder of all.
The review also cites a estimate that the incidence of dystonia amongst professional musicians is around 1%, in comparison to a rate amongst the general US population of 0.03% (and 0.006% in Japan, which is an additional suggestion of a genetic component). 1% seems low to me; we’ve had several cases in my orchestra since I joined 20 years ago.
And the cause?
A lack of inhibition is a common finding in studies of patients with all forms of dystonia… Generally, nervous system function requires a constant, subtle balance between excitation and inhibition in neural circuits. This is particularly important in precise and smooth movements of the hand or the embouchure. For example, rapid individualized finger move- ments in piano playing require selective and specific activation of muscles moving the intended finger in the intended way and inhibiting movements of uninvolved fingers. In patients suffering from hand dystonia, electromyographic recordings revealed abnormally prolonged muscle firing with co-contraction of antagonistic muscles and overflow of acti- vation of inappropriate muscles.
Lack of inhibition is found at multiple levels of the nervous system: At the spinal level, lack of inhibition leads to a reduced reciprocal inhibition of antagonistic muscle groups producing co-contraction, for example, of wrist flexors and extensor muscles, which in turn leads to the feeling of stiff- ness and immobility and frequently to abnormal postures with predominant flexion of the wrist due to the predominance of the stronger flexor muscles.
Abnormal inhibition also has been demonstrated at the cortical level by measuring intracortical inhibition using non- invasive transcranial magnetic stimulation. Interestingly, at the cortical level, abnormal inhibition frequently is seen in both hemispheres, even in patients with unilateral symptoms, hinting at a more generalized nature of the inhibition deficit.
Finally, lack of inhibition was also seen in complex tasks, such as in affected pianists’ scale playing that required movement preparation prior to playing and subsequent sudden movement inhibition when a no-go signal appeared. The ubiquitous demonstration of deficient inhibition is suggestive of a common underlying genetic cause.
But what causes the lack of inhibition? It appears to be a kind of neurological over-use syndrome:
Several studies have demonstrated that the ability to perceive two stimuli as temporally or spatially separate is impaired in patients with musician’s dystonia, be it the fingertips in hand dystonia or the lips in embouchure dystonia. This behavioral deficit is mirrored in findings of the cortical somatosensory representation of fingers or lips. Using evoked potential technology, it was demonstrated that in the somatosensory cortex, the topographical location of sensory inputs from individual fingers overlap more in patients with musician’s cramp than in healthy controls. Similarly, lip representation was altered in patients suffering from embouchure dystonia.
Since in healthy musicians an increase of sensory finger representations has been described and interpreted as adaptive plastic changes to conform to the current needs and experiences of the individual, it could be speculated that these changes develop too far in musicians suffering from dystonia, shifting brain plasticity from a benefit to a maladaptation. In this context, it is worth mentioning that local pain and intensified sensory input due to various origins, such as nerve entrapment, trauma, or overuse, have been described as potential triggers of dystonia. In a large group of musicians suffering from focal dystonia, local pain preceded focal dystonia in 9% of the patients.
Interestingly, there are obvious parallels of abnormal cor- tical processing of sensory information and cortical reorganization in patients with chronic pain and those with focal dystonia. This suggests parallels in the pathophysiological mechanisms in these selected groups of patients. Furthermore, in an animal model of focal dystonia, which was established in overtrained monkeys, repetitive movements induced both types of symptoms, pain syndromes as well as dystonic movements. Brain mapping of the receptive fields demonstrated a distortion of the cortical somatosensory representation, suggesting that overtraining and practice-induced alterations in cortical processing may play a role in focal hand dystonia.
Focal dystonia was induced in overtrained monkeys?
The review’s conclusions don’t offer much hope that the incidence of dystonia in our business is going to diminish any time soon:
In summary, overuse and intense working behavior, spatiotemporal constraints, and special psychological condi- tions, including anxiety and extreme perfectionism, may trig- ger the onset of musician’s focal dystonia on the basis of a given predisposition that may be genetically determined. It should be emphasized that the emotional aspects of music performance, especifically the enormous professional pressure, substantially contribute to stress-induced processes that may foster consolidation of dystonic movements. In part, the unyielding reward and punishment frame in the classical music performance scene provides a fertile ground for these stresses in musicians. This in turn could explain why, for example, improvisational jazz musicians are much less likely to develop musician’s dystonia. Here, as in many other music cultures, reproduction of the precise musical notation plays only a minor role. Learning is frequently based on imitation, and movements frequently can be selected deliberately, obeying the individual’s anatomical prerequisites.
…Concerning prevention, exaggerated perfectionism and anxiety as triggering factors should be addressed in the education of musicians. This has to be started early. From the first lesson on, music educators should strive to create a friendly, supportive atmosphere focusing on creativity, curiosity, and playful experiences in the world of sounds. It is not by chance that we commonly speak of “playing an instrument” and not of “working an instrument.” Of course, structured, goal-directed learning is a prerequisite of musical mastery. Here, reasonable practice schedules, economic technique, prevention of overuse and pain, mental practice, variations of movements patterns, maintenance of motivation and avoidance of mechanical repetitions and frustration, healthy living habits, warm-ups and cool-down exercises, regular physical exercise, and sufficient breaks and sleep are the cornerstones of healthy musical practice.
And, in the real world, technical perfection will remain the way to get hired by an orchestra.