Sensory disinhibition on passive movement in cervical dystonia.

The relevance of the sensory system in the patho- physiology of cervical dystonia (CD) has been discussed since the description of sensory tricks associated with this disorder. Our objective was to locate changes in somatosensory process- ing of patients with CD responding in a passive sensory task of body regions that are not affected by dystonic symptoms. We used functional magnetic resonance imaging (fMRI) in 17 patients with CD and 17 healthy controls performing a strictly passive 30-degree forearm movement task with the left arm. TSUI and TWSTRS rating scales were used for clinical assess- ment. All patients were treated with botulinum neurotoxin type A (BoNT-A; Dysport 1 ). Patients with CD showed BOLD-sig- nal increase in the contralateral primary and secondary sensory cortex, the cingulate cortex and cerebellum bilaterally com- pared to healthy controls. We found a strong positive correla- tion of this activation with BoNT-A dosage in the supplemen- tary motor area (SMA) and a negative correlation with the TWSTRS in that same region. The observed sensory overacti- vation suggests a general disinhibition of the somatosensory system in CD as it was not limited to the motor-system or the direct neuronal representation of the affected dystonic muscu- lature alone. 2010 Movement Disorder Society