Polyelectromyography Under Propofol to Differentiate Functional from Idiopathic Dystonia: A Pilot Study

Background: Functional dystonia (FD) is one of the most diagnostically challenging functional movement disorders. Phenomenological features often lack specificity, as many are also observed in idiopathic dystonia (ID) and validated biomarkers to distinguish FD from ID are currently unavailable. Objective: To investigate potential differences in muscle activity between ID and FD patients using polyelectromyography (PEMG) under anesthesia. Methods: We consecutively enrolled 10 patients with FD and 17 with ID according to the current diagnostic criteria who underwent continuous PEMG before, during, and after propofol infusion. Sedation levels were monitored by electroencephalography and bispectral index and stratified via the Observer's Assessment of Alertness/Sedation Scale (OASS). PEMG recordings were performed under five definite scenarios: alert, mild and deep sedation, and partial and full recovery of consciousness status. Presence/absence of EMG activity was evaluated across these stages, and changes from baseline patterns were analyzed. Results: During mild sedation, EMG activity persisted in all ID (100%) and in 9 (90%) FD patients. During deep sedation, EMG activity persisted in 9 (53%) ID patients and was absent in all FD patients (100%) (P = 0.01). During partial recovery of consciousness, EMG activity was present in all (100%) ID and only in 1 (10%) FD patients (P < 0.001). At full recovery, a different muscular activation pattern from baseline was observed in 7 (70%) FD and only in 1 (6%) ID patients (P = 0.001). Conclusions: EMG silence during deep sedation and partial recovery may serve as a neurophysiological marker of FD. A muscular activation pattern differing from baseline may represent a neurophysiological clue for incongruence © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.