Sensorimotor integration in primary dystonia – its relevance for the sensory trick

1. Sensorimotorintegration in primarydystonia – itsrelevanceforthesensorytrick Dr. Florian Brugger

2. Sensorimotorintegration in primarydystonia – itsrelevanceforthesensorytrick Background Many patients with primary dystonia are aware of a particular manoeuvre like touching the chin in cervical dystonia, which leads to a marked improvement of abnormal posturing. These manoeuvres are referred as sensory trick (ST). The benefit from the ST can be comparable or even better than that of botulinum toxin, the current gold standard treatment in focal dystonia. The ST, however, gets increasingly lost, as the disease progresses. Due to its astonishing impact on the symptoms, the ST is of huge interest for clinicians and dystonia researchers, respectively. Recently, it was show that patients with a ST perform better on temporal discrimination of multimodal stimuli than those without. These tasks basically require an integration of different afferent inputs, most presumably occurring on the cortical level. Therefore, it can be assumed that there is a relevant difference in terms of sensory processing between patients with and without a ST. In the past, many studies using different electrophysiological paradigms showed that disturbed inhibition is a prominent feature in primary dystonia, not only in the motor, but also in the sensory system. Despite the good knowledge about these neurophysiological abnormalities in primary dystonia in general, surprisingly less is known in this regard in the context of ST.

3. Sensorimotorintegration in primarydystonia – itsrelevanceforthesensorytrick Aim The aim of the project is to study the impact of a sensory trick (ST) on sensorimotor integration by using different electrophysiological approaches. It is assumed that the performance of a ST itself leads to a normalization of the respective electrophysiological properties. This improvement, however, might be missing in patients without a ST.

4. Sensorimotorintegration in primarydystonia – itsrelevanceforthesensorytrick Study design/methods The first approach of this project includes a search for those electrophysiological tests which most reliably allows a differentiation between patients with a sensory trick (ST) and without. The test battery comprises different electrophysiological techniques among them different sensory and motor evoked potential paradigms. In a second approach, all patients will undergo repetitive transcranial magnetic stimulation (rTMS). This technique allows the non-invasive modulation of cortical plasticity by the application of magnetic impulses. Those electrophysiological techniques which have turned out to be most reliable in terms of group differentiation will be repeated before and after rTMS. By the means of the selected electrophysiological tests, it will be judged if sensorimotor integration can be restored by rTMS as well as by performing the ST. For this project, patients with cervical dystonia and a ST, patients without a sensory trick and healthy controls will be considered. The project will be conducted at the Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London and will be supervised by Prof. Kailash P. Bhatia and Prof. John C. Rothwell. There will also be a close cooperation with Dr. Georg Kägi, St. Gallen. .

5. Sensorimotorintegration in primarydystonia – itsrelevanceforthesensorytrick Perspective This study can hopefully shed light on the neuronal networks involved in the ST hence contributing to the development of rTMS as a possible future treatment option in primary dystonia. On the one hand, this study can provide evidence for the feasibility of the applied electrophysiological techniques as surrogate markers in treatment studies on the other hand it can yield evidence for the optimal stimulation site for future rTMS studies. .