Objective: To evaluate the relationship between clinical features of dystonia and striatal BOLD activity.

Background: Dystonia is a brain disorder which causes involuntary twisting movements, abnormal postures and pain. Writer’s cramp (WC) is a task specific form of focal hand dystonia which occurs selectively during writing and suggests a problem with the brain’s ability to accurately encode or access motor skill program(1). Development of long-lasting treatments is contingent on understanding the relationship of dystonia circuit abnormalities to disease symptoms. Lesion studies in humans and animal models demonstrated that striatum is a key region of brain impairment in dystonia(2). In human focal dystonia, task-based fMRI studies showed decreased striatal BOLD activity(3). However, much less is known about how abnormal task-based fMRI activity relates to clinical measures of dystonia.

Method: 10 WC, and 9 healthy subjects were clinically phenotyped using automated writing measures into mild or moderate subtypes. All subjects underwent fMRI while performing a series of 3 motor tasks spanning simple to complex in a block design: 1) simple task of finger flexion-extension (FFE) and complex tasks of 2) four-element sequence tapping (4E) and 3) sentence writing (W). For each motor task, a group mean was calculated using general linear model.Changes in BOLD activity in brain regions of interest were extracted using the MNI atlas and compared across the two groups for the three motor tasks. A second analysis was performed to compare BOLD activity between the two subsets of WC subjects (mild vs moderate).

Results: HV subjects demonstrate increase BOLD activity in left striatum during all 3 motor tasks. In contrast, WC subjects show reduction in striatal activity during FFE and W while 4E does not show significant difference between the two groups. Within the WC subsets, there is decline in BOLD activity in the striatum in association with dystonia clinical outcome severity during all 3 motor tasks, with moderate subtype showing greater decline in striatal BOLD activity compared to mild subtype.

Conclusion: Our study demonstrates that clinical measures of dystonia correlate with striatal activity in a dose-dependent manner. These findings augment prior studies identifying striatal dysfunction in dystonia and extend this knowledge by revealing a relationship between striatal activity and clinical disease severity.

References: 1. Albanese A, Bhatia K, Bressman SB, Delong MR, Fahn S, Fung VSC, et al. Phenomenology and Classification of Dystonia : A Consensus Update. 2013;28(7):863–73. 2. Peterson DA, Sejnowski TJ, Poizner H. Convergent evidence for abnormal striatal synaptic plasticity in dystonia. Neurobiol Dis [Internet]. 2010;37(3):558–73. Available from: http://dx.doi.org/10.1016/j.nbd.2009.12.003 3. Gallea C, Horovitz SG, ’Ali Najee-Ullah M, Hallett M. Impairment of a parieto-premotor network specialized for handwriting in writer’s cramp. Hum Brain Mapp. 2016;37(12):4363–75.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/writers-cramp-dystonia-during-increasingly-complex-motor-task-analysis-of-behavior-and-task-fmri/