Abstract Details

Title A Potential Biomarker for Focal Dystonia: Abnormal Dorsal Premotor-Motor Inhibition in Writer's Cramp

Topic Movement Disorders

Presentation(s) S33 - (-)

Poster/Presentation
Number 006

Objective

Background In focal hand dystonia (FHD), a deficient interaction between dorsal premotor and motor cortex could impair the ability of the motor cortex to execute a task-specific movement. In prior work, we showed an abnormal increase in dorsal premotor-motor intracortical inhibition (dPMI) at rest in a surround muscle that was lost at onset of a simple movement. Here we explore the tonic phase of a simple movement and the movement that evokes dystonia.

Design/Methods We studied nine control subjects and nine patients with FHD (writer's cramp). dPMI was tested by applying conditioning transcranial magnetic stimulation to the dorsal premotor cortex and then a test pulse to the ipsilateral motor cortex at an interval of 6ms. dPMI was tested at rest, with contraction of the first dorsal interosseous muscle (FDI) at 10% maximum force and during pen-holding. We also investigated the role of direct premotor cortex to spinal cord modulation using the H-reflex in flexor carpi radialis to prove that any effect would be cortical.

Results Our results show that patients with FHD exhibited dPMI at rest (88.5%, the ratio of conditioned to unconditioned test pulse) in contrast to our controls who did not show dPMI (109.6%) (p=0.0198). This difference between patients and controls persisted during contraction (100% vs. 112%) and pen-holding (95.6% vs. 111%). The H-reflex in the arm was not modulated by the premotor cortex stimulation.

Conclusions These results suggest that abnormal premotor-motor interactions may play a role in the pathophysiology of focal dystonia. dPMI was not modulated in either group, but was constantly greater in the patients. The significance of the increased inhibition is not clear and might be compensatory. It appears to be a robust finding and could be further explored as a biomarker.

Authors/Disclosures
Sarah Pirio Richardson, MD, FAAN PRESENTER	Dr. Pirio Richardson has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Jazz Pharmaceuticals. Dr. Pirio Richardson has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for NIH/NINDS. The institution of Dr. Pirio Richardson has received research support from NIH. The institution of Dr. Pirio Richardson has received research support from DOD. The institution of Dr. Pirio Richardson has received research support from Scion. The institution of Dr. Pirio Richardson has received research support from Jazz Pharmaceuticals. The institution of Dr. Pirio Richardson has received research support from UCB. The institution of Dr. Pirio Richardson has received research support from Buk-wang Pharmaceuticals.
	No disclosure on file
	No disclosure on file
Mark Hallett, MD, FAAN (National Institutes of Health)	Dr. Hallett has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Janssen. Dr. Hallett has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Neurocrine. Dr. Hallett has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Brainsway. Dr. Hallett has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for VoxNeuro. Dr. Hallett has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for QuantalX. Dr. Hallett has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Elsevier. Dr. Hallett has received intellectual property interests from a discovery or technology relating to health care. Dr. Hallett has received publishing royalties from a publication relating to health care. Dr. Hallett has received publishing royalties from a publication relating to health care. Dr. Hallett has received publishing royalties from a publication relating to health care. Dr. Hallett has received publishing royalties from a publication relating to health care. Dr. Hallett has received personal compensation in the range of $500-$4,999 for serving as a Speaker with International Parkinson and Movement Disorder Society. Dr. Hallett has a non-compensated relationship as a Past-President with Functional Neurological Disorder Society that is relevant to AAN interests or activities.
Alessia Di Sapio	Alessia Di Sapio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Roche . Alessia Di Sapio has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion . Alessia Di Sapio has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Merck. Alessia Di Sapio has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Novartis. Alessia Di Sapio has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Sanofi . The institution of Alessia Di Sapio has received research support from Ministero della Salute. The institution of Alessia Di Sapio has received research support from Sanofi.

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