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| Diane Ruge |
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University of Frankfurt/Main, Dpt. of Neurology, Schleusenweg 2-16, 60528 Frankfurt/Main, Germany
e-mail: druge@web.de |
Poster Presentation: |
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| DYSFUNCTIONAL CONNECTIVITY AT THE INTERFACE BETWEEN SMA/PMA AND PRIMARY MOTOR CORTEX IN PATIENTS WITH WRITER’S CRAMP. |
| Diane Ruge, Kirn Kessler, Ulf Ziemann | |
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niversity of Frankfurt Main, Dpt. of Neurology, Germany |
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| Dysfunctional connectivity at the interface between SMA/PMA and primary motor cortex in patients with writer’s cramp
The precise pathophysiology of focal dystonias is still unknown. Although they are commonly regarded as basal ganglia disorders, several lines of evidence indicate impaired cortical function. Furthermore, the task-specificity in focal dystonias like writer´s cramp is not understood.
Cortical regions like the supplementary motor areas (SMA) and premotor areas (PMA) play an important role in the performance and learning of skillful hand movements such as writing. Therefore, the inter-communication between these areas and the primary motor cortex (M1) could be highly relevant for the development and maintenance of dystonic movements.
The aim of our study was to investigate inter-regional functional connectivity between M1 and SMA/PMA in patients with writer´s cramp compared to healthy controls, during execution of a (complex) writing task versus execution of a (simple) wrist extension movement. The main question was: Is there a pathological, task-specific change of inter- communication between M1 and SMA/PMA in the writer’s cramp patients?
Methods: We studied 8 controls and 5 patients (all right-handers). We recorded EEG from 56 scalp electrodes and analysed task-related partial coherence (TRPCoh), which is a measure of the coupling between two signals at any given frequency. Here, we focused on the high alpha-band (10-12 Hz). Both movement-tasks were carried out self-paced approximately every 10 sec. with the right hand. At least 100 movement trials were analysed for each subject and movement condition.
Results: For the wrist-extension task, patients and controls showed a very similar pattern of TRPCoh changes between M1 and SMA/PMA. TRPCoh started to increase at around 1.5 sec. before movement onset, peaked shortly after movement onset and then decreased slowly. For the writing task, the pre-movement TRPCoh increase between M1 and SMA/PMA was again similar in both groups, but at around movement onset TRPCoh completely collapsed in the patients while TRPCoh further increased in the controls.
Conclusions: In patients with writer´s cramp, specifically during writing, a clear break-down of inter-regional connectivity between M1 and SMA/PMA was observed at around the time of movement onset. This suggests that a dysfunctional communication at the interface between M1 and SMA/PMA plays an important role in the pathophysiology of task-specific dystonia.
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