Characteristics of sensory trick-like manoeuvres in jaw-opening dystonia.

We evaluated the effect of different manipulations on the performance of a standardized counting task in 7 patients with idiopathic jaw-opening dystonia. Patients used a small stick as sensory stimulus. Following conditions were examined: stick placed between teeth and cheek (CHEEK), biting on stick (TEETH), voluntary jaw occlusion without stick (OCCLUSION). Articulation was rated by patients and experimenters and surface electromyographic activity (EMG) was recorded. Patient-rating (CHEEK - 36.6%, TEETH - 48.1%) and EMG (-18.1%; -17.3%) were significantly improved for conditions using the stick, whereas experimenter-rating showed a trend for TEETH (-16.2%). Although jaw occlusion during speaking deteriorates articulation in healthy subjects, there was no further deterioration in patients and EMG was even significantly reduced (-18.6%). Comparable results were obtained in 1 patient using a special dental device. We conclude that sensory tricks significantly improve subjective and objective parameters. Besides tactile stimulation, altered proprioceptive feedback and antagonist activation may modulate hyperactive dystonic networks.