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Myoclonus-dystonia is an autosomal dominantly inherited movement disorder clinically characterized by myoclonic jerks and dystonic movements of the upper body. Functional imaging and structural gray matter imaging studies in M-D suggest defective sensorimotor integration and an association between putaminal volume and severity of dystonia, possibly because of neuronal plasticity. As we expect changes in the connections between the cortical and subcortical regions, we performed a combination of white matter voxel-based morphometry (wVBM) and diffusion tensor imaging (DTI) to detect macro- and microstructural white matter changes, respectively, in DYT-11 mutations carriers (M-D). Sixteen clinically affected DYT-11 mutation carriers and 18 control subjects were scanned with 3-Tesla MRI to compare white matter volume, fractional anisotropy, and mean diffusivity between groups. In DYT11 mutation carriers, increased white matter volume and FA and decreased mean diffusivity were found in the subthalamic area of the brain stem, including the red nucleus. Furthermore, decreased mean diffusivity was found in the subgyral cortical sensorimotor areas. The white matter changes found in the subthalamic area of the brain stem, connecting the cerebellum with the thalamus, are compatible with the hypothesis that abnormal function in M-D involves a network that includes the cerebellum, brain stem, and basal ganglia. Whether these changes are causative or an effect of M-D requires further study., (Copyright © 2012 Movement Disorder Society.)

Objective: The aim of the present study is to investigate cortical excitability in patients with DYT 11 positive Myoclonus-Dystonia (M-D), using transcranial magnetic stimulation (TMS)., Methods: Silent period, motor evoked potential (MEP) recruitment curve, short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and short interval intracortical facilitation (SICF), with short interstimulus intervals (ISIs) ranging from 1.2 to 3.2 ms, were studied in 15 DYT 11-positive M-D patients and their matched controls. In four patients and matched controls peripheral double pulse electrical nerve stimulation was performed., Results: All TMS parameters of cortical excitability were normal compared to healthy controls. In the SICF protocol we observed more variable and polyphasic MEPs in M-D patients. Cross-covariance analysis of MEP area revealed a significant correlation difference at ISI 2.2 and 2.8 ms. This increased variability was not seen in other TMS protocols or with peripheral nerve stimulation., Conclusions: In contrast with other types of dystonia, no changes in cortical excitability were found in DYT 11 patients. Our findings suggest that M-D is both clinically and pathophysiologically a separate entity from other dystonic disorders. Polyphasic MEPs during the SICF protocol in M-D patients could reflect central neuron membrane instability. Application of the SICF protocol in other patient groups has to prove its value in movement disorders.