Clinical Research Directory

VTS Sensorimotor Neuromodulation in WC

Sponsor: Ottawa Hospital Research Institute

Summary

Writer's cramps (WC) is a focal task-specific upper limb dystonia that significantly impairs handwriting and other manual skills, affecting functionality. WC is one of the most common task-specific dystonias, affecting 3.8-80 per million individuals. The first-line management option is botulinum toxin injections in the muscles affected by the involuntary movements, causing a transient neuromuscular blocking effect and reducing muscle abnormal contraction. However, the effect lasts for around 3 months or less, is invasive, may cause unintended hand weakness, and the benefits are variable in terms of the severity of dystonic contraction and functional gain. Focal limb dystonia pathophysiology, including writer's cramps, has been linked to propriospinal signalling defects in the sensorimotor cortex modulation5, prompting an investigation into neuromodulation of this region as a modality for dystonia management. Other forms of dystonia have shown a reduction of the involuntary movements with vibrotactile stimulation (VTS), including cervical and laryngeal dystonia8. These results have supported the hypothesis that VTS alters the abnormal output of mechanical receptors from proprioceptive and tactile pathways to the sensorimotor cortex.Changes in neurophysiological markers of dystonia in the sensorimotor cortex also corroborated the modulatory effect. Furthermore, more invasive methods of neuromodulation, such as Globus Pallidus internus Deep Brain Stimulation, are known to be an effective treatment option for medically refractory dystonia, with evidence of promoting a similar result on the sensorimotor pathway via cortico-basal ganglia network direct stimulation. Finally, one of the most common ways of modulation is a core feature in dystonia, which is called an alleviating manoeuvre (AM) or geste antagoniste. This comprises a sensory or motor stimulation located in the anatomical area of the dystonia, which will transiently alleviate the involuntary movement. In that case, Functional MRI studies also suggest a sensorimotor network modulation in AM. Thus, there is considerable preliminary evidence to suggest the role of invasive and non-invasive neuromodulation in the treatment of dystonia. Given the variable and often suboptimal response to standard treatments for task-specific dystonia, such as WC, and the associated functional impairment, this study explores the role of vibrotactile stimulation (VTS) as a non-invasive neuromodulation tool for WC. VTS targets muscles involved in dystonic contractions, intending to create a non-invasive neuromodulation via propriospinal pathways to the sensorimotor cortex and improve motor control in individuals with WC. The effect described in previous studies lasts around 20-30 minutes, which should allow functionality for handwriting during that period of time. In the future, with the refinement of the technique's effectiveness, it could be escalated for a wearable treatment option. Based on the clinical and pathophysiological characteristics of task-specific dystonia it is reasonable to use a peripheral sensory modulation technique to try and reduced the abnormal motor cortical output this way reducing the dystonic movement. That has been proved successful in other types of dystonia. Thus, a pilot study for proof-of-concept concept and feasibility is a good first step towards that direction.

Official title: Vibro-tactile Stimulation Sensorimotor Neuromodulation in Writer's Cramps: a Pilot Study

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