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Introduction Although sensory tricks are well known as the maneuvers that temporarily relieve dystonic symptoms in patients with cervical dystonia (CD), the underlying neurophysiological mechanisms remain unclear. We aimed to investigate brain potentials related to sensory tricks in patients with CD. Methods Thirteen patients with CD and 13 age-matched healthy volunteers participated. The experiment consisted of three conditions (moving the neck, moving an arm, and performing sensory tricks) presented in different blocks in random order in a contingent negative variation (CNV) paradigm. Warning and trigger stimuli (S1 and S2) were presented to the participants, who were instructed to prepare to perform the specific task for each condition after S1, and then to perform the task after S2. Early and late components of the CNV were measured. Results The late CNVs in patients with CD were significantly larger than those in healthy participants in Fz, FCz, Cz, and C3 electrodes. Only in patients with CD, the late CNVs were significantly greater for the ‘sensory tricks’ condition compared to the ‘move neck’ condition in Fz and C3 electrodes. Conclusion The late CNV is increased during sensory tricks in patients with CD, suggesting that sensory tricks may affect mechanisms related to the motor preparatory phase in the premotor and primary motor areas. Sensory tricks may normalize impaired motor preparation in dystonia, leading to improved dystonic symptoms.

Rapid eye movement sleep behavior disorder (RBD) is commonly accompanied in Parkinson disease (PD). However, the underlying mechanism linking RBD to PD remains unclear. We interviewed and examined 447 consecutive patients with PD to investigate factors associated with the presence of RBD in PD patients. Using the minimal diagnostic criteria for parasomnias provided in the International Classification of Sleep Disorders-Revised (ICSD-R), 164 patients (36.5%) were diagnosed with clinically probable RBD (cpRBD). PD patients with cpRBD were older, had a longer duration of PD, a more severe level of disability, a longer duration of antiparkinsonian medication, and a lower proportion of their Unified Parkinson Disease Rating Scale (UPDRS) scores accounted for by tremor than those without RBD. Multivariate and univariate logistic regression analyses revealed that patient age, PD symptom duration (and, accordingly, more severe motor disability), tremor score, and proportion of the UPDRS score accounted for by tremor were significant factors associated with the presence of RBD in PD patients. The results of the present study support previous observations that PD with RBD may result from a different underlying pattern of neurodegeneration than PD without RBD.