Objective: Writer's cramp (WC) is a focal task-specific dystonia characterized by abnormal posturing of the hand muscles during handwriting, but not during other tasks that involve the same set of muscles and objects such as sharpening a pencil. Our objective was to investigate the pathophysiology underlying the task specificity of this disorder using EEG. We hypothesized that premotor-parietal connectivity will be lower in WC patients specifically during handwriting and motor imagery of handwriting.
Methods: We recruited 15 WC patients and 15 healthy controls. EEG was recorded while participants performed 4 tasks - writing with a pencil, sharpening a pencil, imagining writing and imagining sharpening. We determined the connectivity changes between relevant brain regions during these tasks.
Results: We found reduced interhemispheric alpha coherence in the sensorimotor areas in WC patients exclusively during handwriting. WC patients also showed less reduction of task-related beta spectral power and a trend for reduced premotor-parietal coherence during motor tasks.
Conclusion: We could not confirm an abnormality in premotor-parietal connectivity specific to handwriting by this method. However, there was a task-specific reduction in interhemispheric alpha connectivity in WC patients, whose behavioral correlate remains unknown.
Significance: Interhemispheric alpha connectivity can be a potential interventional target in WC.
Keywords: EEG; Focal task specific dystonia; Functional connectivity; Interhemispheric coherence; Writer’s cramp.
Copyright © 2020. Published by Elsevier B.V.