The owl monkey model of focal dystonia has allowed investigators to verify the hypothesis that somatic sensory abnormalities are part of the disorder. This chapter reviews the evidence of mechanisms underlying sensory and motor disorders and shows that a common cortical abnormality may underlie both disorders. Treatments that focus first on treating sensory deficits and later progress to sensory-motor integration and sensory-motor deficits have high efficacy in restoring predystonic motor function. The chapter discusses how the range of documented physiological motor and sensory deficits in focal hand dystonia relate to poor motor function. Focal dystonia is a movement disorder in which muscles are abnormally synchronized and normal muscle antagonists may be co-active. Focal dystonia affects significant fractions of subpopulations that perform repetitive stereotyped motor actions with their hands, particularly musicians and typists. In addition, other groups, such as athletes, particularly those who powergrip during shoulder motions, may be affected. This chapter unequivocally demonstrates that abnormalities occur in sensory representations in focal hand dystonia, and that addressing these abnormalities as a first step in treatment can greatly benefit the patient population. Treatment strategies based, in part or in whole, on restoring sensory function have positively affected patient populations. As this work progresses, the combined synergy of the human studies and animal work should serve to greatly reduce the impact of focal hand dystonia on the population.
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