Reversal of Temporal Discrimination in Cervical Dystonia after Low-Frequency Sensory Stimulation

Background: Somatosensory temporal discrimination is abnormal in dystonia and reflects reduced somatosensory inhibition. In healthy individuals, both the latter are enhanced by high-frequency repetitive somatosensory stimulation, whereas opposite effects are observed in patients with cervical dystonia. Objectives: We tested whether low-frequency repetitive sensory stimulation, which in healthy individuals worsens discrimination, might have the opposite effect in patients with cervical dystonia at the physiological level and, in turn, improve their perceptual performance. Methods: Somatosensory temporal discrimination and several electrophysiological measures of sensorimotor inhibition were collected before and after 45 minutes of low-frequency repetitive sensory stimulation. Results: As predicted, and opposite to what happened in controls, low-frequency repetitive sensory stimulation in patients enhanced sensorimotor inhibition and normalized somatosensory temporal discrimination. Conclusions: Patients with cervical dystonia have an abnormal response to repetitive sensory stimulation, which we hypothesize is attributed to abnormally sensitive homeostatic mechanisms of inhibitory circuitry in both sensory and motor systems.