Objective: The goal of the current study was to assess task-related brain activity in patients with cervical dystonia (CD) using functional magnetic resonance imaging (fMRI) with and without a single-dose administration of trihexyphenidyl.

Background: CD is the most common type of primary dystonia, and is characterized by involuntary neck muscle contractions that cause abnormal movements of the neck and head. Currently, there is no FDA approved oral medication for CD. Anticholinergic agents such as trihexyphenidyl are sometimes used. As yet, no study has investigated how anticholinergics modulate brain activity in CD.

Methods: A grip force production task known to extensively engage motor brain networks was performed in a 3T MRI scanner by 16 patients with idiopathic CD, and 16 age- and gender-matched healthy individuals. CD patients were scanned twice, off-medication, and on average two hours after a single-dose (2 mg) administration of trihexyphenidyl. Control subjects did not receive the medication, and were therefore only scanned once.

Results: Off-medication, CD patients had reduced motor-related activity compared to healthy individuals in the contralateral primary motor and somatosensory cortices, middle frontal gyrus, and insula, and increased activity in the ipsilateral pre-supplementary motor area, superior parietal lobule, and contralateral lobules V, I-IV of the cerebellum. Administration of trihexyphenidyl to CD patients was associated with an increase in the motor-related activity of the primary somatosensory cortex, bilaterally, and contralateral middle frontal gyrus as compared to the off-medication state.

Conclusions: These results suggest a baseline disruption of somatosensory processing in CD that can be modulated acutely by administration of trihexyphenidyl.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/motor-related-brain-changes-associated-with-acute-administration-of-trihexyphenidyl-in-patients-with-cervical-dystonia/