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Abstract & Commentary
Source: Priori A, et al. Neurology. 2001;57:405-409.
Focal task-specific dystonia (FTSD) is one of the most interesting and mysterious neurologic disorders. Affected patients are otherwise completely well, but are unable to perform a specific skilled manual task. By definition, FTSD affects only 1 part of the body (usually the hand) and is limited to the performance of a specific task. Writer’s cramp is the most common FTSD, although the disorder has been described in professional sewers, tailors, engravers, golfers, and virtually all types of musicians (pianists, violinists, guitarists, flutists, clarinetists, drummers, etc).
Until recently, little was known about the mechanisms underlying FTSD. Recent work in patients with FTSD and in primates with focal dystonia of the hand has demonstrated that the cortical sensory representation of the affected hand is markedly abnormal. These findings are similar to the altered cortical sensory maps seen in patients who have undergone limb amputations. Fluoro-deoxyglucose PET scanning and functional magnetic resonance imaging has demonstrated that patients with FTSD inappropriately activate cortical regions (typically supplementary motor cortex) that are not activated during normal performance of manual tasks.
The treatment of FTSD remains challenging. Oral medications commonly used to treat generalized dystonia (such as trihexyphenidyl, baclofen, and clonazepam) are usually not helpful. Injection of botulinum toxin into the affected limb offers substantial functional improvement, particularly in patients with writer’s cramp. However, for professional musicians and professionals such as surgeons who rely on accurate and exquisitely controlled complex movements, these treatments remain sufficiently active to prevent them to return to professional life.
The current paper outlines a new technique for the treatment of FTSD—limb immobilization. In this study, Priori and colleagues recruited 7 musicians with FTSD and 1 patient with writer’s cramp, all of whom had failed standard therapies for focal dystonia. The arm affected with dystonia was then immobilized for 5 weeks in a rigid splint. Patients were allowed to remove the splint only once per week to attend to hygiene. At the end of the 5-week period, the splint was removed and patients were allowed to use the hand and to resume practicing their instrument. They were assessed over the ensuing 24 weeks with videotaped examinations, and 2 blinded observers used several functional disability scales to rate the patients before and at multiple points after treatment.
Immediately after the splint was removed, all patients reported clumsiness and mild-to-moderate weakness in the limb. Joint edema and pain were common, and nail growth stopped. Four weeks after splint removal, voluntary control and strength in the hand had returned to normal. Three patients had a moderate improvement in focal dystonia, and 4 had a marked improvement, sufficiently good enough to allow public performance. The patients with the most severe dystonia enjoyed the greatest improvement, and 1-year follow-up benefits have been maintained.
This report is of considerable interest to movement disorder neurologists and also to those in the neurologic community interested in cortical plasticity. In the last decade, there has been increasing evidence that the adult brain is capable of remarkable plasticity. While Priori et al did not perform functional imaging on their patients, the simplest and most logical explanation for their success is that the 5-week immobilization period reversed or obliterated the aberrant cortical representation of dystonia. In a sense, Priori et al succeeded in resetting the sensory-motor cortex by subjecting patients to a period of profound sensory and motor deafferentation.
This report is preliminary and further studies are warranted. Immobilizing a limb entails the risk of nerve entrapment, muscle atrophy, or, in the worst-case scenario, development of reflex sympathetic dystrophy. However, compared to virtually all other available treatments for FTSD, limb immobilization offers the potential to dramatically improve or even cure focal dystonia. For this reason, this paper offers hope to a frustrated population of professionals whose careers and livelihoods are threatened by this unusual condition. —Steven Frucht
Frucht, MD, Assistant Professor of Neurology, Movement Disorders Division, Columbia-Presbyterial Medical Center, is Assistant Editor of Neurology Alert.