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Botulinum neurotoxin treatment improves force regulation in writer's cramp.

ABSTRACT: Writer's cramp patients show poor force regulation during handwriting, but also in other experimental tasks requiring fine motor control. Botulinum neurotoxin (BoNT) treatment is clinically effective in a substantial portion of writer's cramp patients, but the full mechanism of action remains enigmatic. BoNT possibly influences ?- and ?-motoneurons through chemodenervation not only of extra-, but also intrafusal muscle fibres and might thus influence muscle spindle afferents. Hence, BoNT weakens injected muscles, but may also modulate sensory aspects of force control. Ten patients and 18 controls pressed their index finger on a force sensor tracking two visual targets: The first target consisted of five plateaus with successively higher force levels and alternated with ascending ramps. In the second target condition the same successive plateaus were to be reached by abrupt jumps. The generated force displayed as a time dependant curve. Root mean square of the difference between target and produced force level was calculated for each plateau/ramp/jump. Patients were treated with BoNT at week 4 and measured at baseline, weeks 2, 4, 6 and 8. Disturbed force regulation in patients for the plateaus and the second jump at baseline resolved after BoNT treatment, and the root mean square of force deviation decreased for the ramps. Fine force control was within the 95% confidence interval of the control group after treatment. In conclusion, force regulation was disturbed in patients and improved after BoNT treatment. This is not compatible with a simple muscle weakening and might thus reflect improved sensorimotor integration.

SUBMITTER: Zeuner KE

PROVIDER: S-EPMC4149416 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Botulinum neurotoxin treatment improves force regulation in writer's cramp.

Zeuner Kirsten E KE Knutzen Arne A Pedack Lucas L Hallett Mark M Deuschl Günther G Volkmann Jens J

Parkinsonism & related disorders 20130316 6

Writer's cramp patients show poor force regulation during handwriting, but also in other experimental tasks requiring fine motor control. Botulinum neurotoxin (BoNT) treatment is clinically effective in a substantial portion of writer's cramp patients, but the full mechanism of action remains enigmatic. BoNT possibly influences α- and γ-motoneurons through chemodenervation not only of extra-, but also intrafusal muscle fibres and might thus influence muscle spindle afferents. Hence, BoNT weakens ...[more]

PMID: 23507416

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Project description:Humans have a distinguishing ability for fine motor control that is subserved by a highly evolved cortico-motor neuronal network. The acquisition of a particular motor skill involves a long series of practice movements, trial and error, adjustment and refinement. At the cortical level, this acquisition begins in the parieto-temporal sensory regions and is subsequently consolidated and stratified in the premotor-motor cortex. Task-specific dystonia can be viewed as a corruption or loss of motor control confined to a single motor skill. Using a multimodal experimental approach combining neuroimaging and non-invasive brain stimulation, we explored interactions between the principal nodes of the fine motor control network in patients with writer's cramp and healthy matched controls. Patients and healthy volunteers underwent clinical assessment, diffusion-weighted MRI for tractography, and functional MRI during a finger tapping task. Activation maps from the task-functional MRI scans were used for target selection and neuro-navigation of the transcranial magnetic stimulation. Single- and double-pulse TMS evaluation included measurement of the input-output recruitment curve, cortical silent period, and amplitude of the motor evoked potentials conditioned by cortico-cortical interactions between premotor ventral (PMv)-motor cortex (M1), anterior inferior parietal lobule (aIPL)-M1, and dorsal inferior parietal lobule (dIPL)-M1 before and after inducing a long term depression-like plastic change to dIPL node with continuous theta-burst transcranial magnetic stimulation in a randomized, sham-controlled design. Baseline dIPL-M1 and aIPL-M1 cortico-cortical interactions were facilitatory and inhibitory, respectively, in healthy volunteers, whereas the interactions were converse and significantly different in writer's cramp. Baseline PMv-M1 interactions were inhibitory and similar between the groups. The dIPL-PMv resting state functional connectivity was increased in patients compared to controls, but no differences in structural connectivity between the nodes were observed. Cortical silent period was significantly prolonged in writer's cramp. Making a long term depression-like plastic change to dIPL node transformed the aIPL-M1 interaction to inhibitory (similar to healthy volunteers) and cancelled the PMv-M1 inhibition only in the writer's cramp group. These findings suggest that the parietal multimodal sensory association region could have an aberrant downstream influence on the fine motor control network in writer's cramp, which could be artificially restored to its normal function.

Dataset Information

Botulinum neurotoxin treatment improves force regulation in writer's cramp.

Publications

Botulinum neurotoxin treatment improves force regulation in writer's cramp.

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