Abstract Myoclonus-dystonia is a hyperkinetic movement disorder and approximately half of myoclonus-dystonia patients have a mutation in the epsilon-sarcoglycan (SGCE) gene, while the remaining cases often have undetermined causative genes. This study aims to assess brain metabolic function in myoclonus-dystonia patients with and without SGCE mutations and compare them to a control group. This study is part of the Next Move in Movement Disorders (NEMO) observational study. We included 23 myoclonus-dystonia patients (11 with SGCE mutations and 12 without) and 23 age-matched controls. Participants underwent 18-Fluordeoxyglucose-PET (18FFDG-PET) and anatomical MRI scans. Data were analysed using a voxel-based analysis and a volume of interest (VOI)-based analysis. In the voxel-based analyses, trends towards differences in the supplementary motor area, cingulate gyrus, parietal and occipital lobe were found. When comparing mutation-positive with mutation-negative patients, trends towards differences in the parietal lobe and precentral gyrus were detected. Symptom severity was correlated with changed metabolism in postcentral and supramarginal gyrus, occipital, and frontal lobe, cerebellum, and caudate nucleus. In addition, VOI-based analyses showed statistically significant differences in the supplementary motor area comparing myoclonus-dystonia patients to controls. The identified trends of increased metabolism in the (pre)motor cortex areas fit the model of a more ‘excitable’ state with a lower activation threshold, possibly due to reduced inhibition from the cerebellum and striatum, regions in which we found a negative correlation between symptom severity and metabolism. Differences were also observed in sensory areas such as the parietal lobe and visual cortex. While the phenotype of SGCE mutation-positive and mutation-negative groups is similar, subtle differences suggest distinct endophenotypes.
Timmers et al. (Tue,) studied this question.