Increased volume and impaired function: the role of the basal ganglia in writer's cramp
Kirsten E. Zeuner3 
Arne Knutzen3 
Oliver Granert3 
Julia Götz3 
Stephan Wolff2 
Olav Jansen2 
Dirk Dressler1 
Harald Hefter4 
Mark Hallett5 
Günther Deuschl3 
Thilo van Eimeren3 
[1] Movement Disorders Section, Department of Neurology, Hannover Medical School, Hannover, Germany;Department of Neuroradiology, Kiel University, Kiel, Germany;Department of Neurology, Kiel University, Kiel, Germany;Department of Neurology, University of Düsseldorf, Düsseldorf, Germany;Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
The pathophysiology of writer's cramp, a task-specific dystonia, remains unclear. The objective of this study was to investigate the basal ganglia circuit and the cerebellum during a complex motor sequence learning task carried out with the nonaffected hand in writer's cramp patients.
Methods
We applied structural and functional imaging in 22 writer's cramp patients and 28 matched controls using 3T MRI. With the asymptomatic left hand all participants learned a complex, sequential, five-element sequence-tapping task as accurately and quickly as possible. Functional imaging was measured during a repeated (15 times), fixed block design with tapping (30 sec) and rest (30 sec). Additionally, gray matter volume of the basal ganglia was analyzed using voxel-based morphometry (VBM).
Results
While behavior was comparable between groups, after small volume correction the anterior part of the right putamen and the left globus pallidus exhibited reduced blood oxygen level-dependent (BOLD) activity in patients during the sequential finger-tapping task. VBM analysis showed larger gray matter volume bilateral in the posterior part of the putamen and globus pallidus. There were no group differences in the cerebellum.
Conclusion
The results indicate an impairment of anterior basal ganglia loops involved in producing complex sequential movements of the unaffected hand. These findings are in line with previous reports of reduced neuronal activity in the globus pallidus internus. Higher gray matter volume of the putamen and globus pallidus may stem from elevated activity of the direct pathway, which could reflect a compensatory phenomenon or a primary predisposition, that is, endophenotypic trait.