Sensory tricks in primary cervical dystonia depend on visuotactile temporal discrimination.

A characteristic feature of primary cervical dystonia is the presence of "sensory tricks" as well as the impairment of temporal and spatial sensory discrimination on formal testing. The aim of the present study was to test whether the amount of improvement of abnormal head deviation due to a sensory trick is associated with different performance of temporal sensory discrimination in patients with cervical dystonia. We recruited 32 patients with cervical dystonia. Dystonia severity was assessed using the Toronto Western Spasmodic Torticollis Rating Scale. Patients were rated according to clinical improvement to a sensory trick and assigned to 1 of the following groups: (1) no improvement (n = 6), (2) partial improvement (n = 17), (3) complete improvement (n = 9). Temporal discrimination thresholds were assessed for visual, tactile, and visuotactile modalities. Disease duration was shorter (P = .026) and dystonia severity lower (P = .033) in the group with complete improvement to sensory tricks compared with the group with partial improvement to sensory tricks. A significant effect for group and modality and a significant interaction between group × modality were found, with lower visuotactile discrimination thresholds in the group with complete improvement to sensory tricks compared with the other groups. In primary cervical dystonia, a complete resolution of dystonia during a sensory trick is associated with better visuotactile discrimination and shorter disease duration compared with patients with less effective sensory tricks, which may reflect progressive loss of adaptive mechanisms to basal ganglia dysfunction.