Electrophysiological evalution of sensory-motor integration in cervical dystonia

Cervical dystonia is a focal dystonia that affects muscles of neck and shoulder, and it causes characteristically recurrent tonic and clonic movements lead to abnormal head postures. There are various studies about excitability in focal dystonia using single and paired pulse transcranial magnetic stimulations (TMS) in the literature. The aim of our study was to compare short latency intracortical inhibition (SICI), intracortical facilitation (ICF) and the cortical silent period (CSP) data that obtained using single and double pulse transcranial magnetic stimulations on sternocleidomastoid muscle in cervical dystonia patients with the data obtained from healthy individuals and thus to investigate patophysiological changes in excitatory and inhibitory circuits in patients. 20 patients and 21 healthy induvidials enrolled in the study. In the studies using double pulse TMS, mainly, there were applied test stimulus with specific interstimulus intervals after conditioning stimulus and obtained amplitude of MEP responses compared with amplitude of MEP responses that obtained by applying test stimuli alone without contidioning stimulus. Cortical silent period was measured in patients and healthy controls. In conclusion cortical inhibition reflected by SICI and CSP parameters was decreased (dysinhibiton) at cervical dystonia patients at SCM muscle which was responsible from the direction of the dystonic neck movements. These findings were more significant at dystonic patients that were not treated with BoTN-A. These findings support the role of dysinhibiton in pathophysiology of dystonia as well as the effect of BoTN-A on cortical plasticity probably by changing the sensorial inputs.