Brain Advance Access originally published online on July 19, 2006
Brain 2006 129(10):2697-2708; doi:10.1093/brain/awl181
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The basal ganglia are hyperactive during the discrimination of tactile stimuli in writer's cramp
1 Department of Neurology, Christian-Albrechts-University Kiel Kiel, Germany 2 NeuroImageNord Hamburg-Kiel-Lübeck Lübeck, Germany 3 Department of Neurology Hamburg University, Hamburg, Germany 4 Department of Neuroscience, Psychiatric and Anaesthesiological Sciences University of Messina, Messina, Italy 5 Human Motor Control Section, Medical Neurology Branch National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
Correspondence to: Prof. Dr Hartwig Roman Siebner, Department of Neurology, Christian Albrechts-University Kiel, Schittenhelmstrasse 10, 24105 Kiel, Germany E-mail: h.siebner{at}neurologie.uni-kiel.de
Writer's cramp is a focal hand dystonia that specifically affects handwriting. Though writer's cramp has been attributed to a dysfunction of the basal ganglia, the role of the basal ganglia in the pathogenesis of writer's cramp remains to be determined. Seventeen patients with writer's cramp (nine females; age range: 24–71 years) and 17 healthy individuals (six females; age range: 27–68 years) underwent functional MRI (fMRI) while they discriminated the orientation of gratings delivered to the tip of the right index finger. Statistical parametric mapping was used to analyse the fMRI data. The significance level was set at a corrected P-value of 0.05. Relative to healthy controls, patients with writer's cramp showed a widespread bilateral increase in task-related activity in the putamen, caudate nucleus, internal globus pallidus and lateral thalamus. In these areas, hyperactivity was more pronounced in patients who had recently developed writer's cramp. The enhanced response of the basal ganglia to tactile input from the affected hand is compatible with the concept of impaired centre–surround inhibition within the basal ganglia–thalamic circuit and may lead to an excessive activation of sensorimotor cortical areas during skilled movements affected by dystonia. Outside the basal ganglia, dystonic patients showed task-related overactivity in visual cortical areas, left anterior insula and right intraparietal sulcus, but not in the primary or secondary sensory cortex. In addition, task-related activity in the cerebellar nuclei, posterior vermis, right paramedian cerebellar hemisphere and dorsal pons was inversely related with the severity of hand dystonia. Regional activity in these areas may reflect secondary adaptive reorganization at the systems level to compensate for the dysfunction in the basal ganglia–thalamic loop.
Key Words: basal ganglia; focal hand dystonia; functional MRI; tactile discrimination; thalamus; writer's cramp
Abbreviations: ADDS, Arm Dystonia Disability Scale; BOLD, blood oxygen level-dependent; fMRI, functional MRI; SPM, statistical parametric map
Received March 25, 2006. Revised June 2, 2006. Accepted June 13, 2006.
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