Sensory tricks initiating before skin contact: New observations in drug-induced tardive dystonia

Dystonia is a movement disorder characterized by involuntary, sustained, or intermittent muscle contractions that often involve abnormalities in sensorimotor integration. Sensory tricks, in which a new sensory input can temporarily correct erroneous motor output, are hallmarks of dystonia. However, the underlying mechanism remains unclear. Here, we report a case of drug-induced tardive dystonia in which the sensory trick effect began before physical contact, providing new insights into its anticipatory processes. A 17-year-old boy with intellectual disabilities, autism, and behavioral disorders developed torticollis and scoliosis after prolonged treatment with risperidone and levomepromazine. The symptoms included neck muscle co-contraction, leftward rotation, and compensatory scoliosis. A sensory trick was observed; light hand contact with the occiput improved the symptoms. However, the video analysis revealed that symptom relief began during arm movements before physical contact. This suggests the role of proprioception, motor preparation, and motor imagery in the sensory trick phenomenon. Discontinuation of the antipsychotics gradually resolved the symptoms. This report highlights a crucial observation: sensory tricks begin before actual tactile contact, emphasizing the role of proprioceptive signals and motor planning in symptom relief. Anticipatory sensory processing suggests a broader mechanism that extends beyond tactile stimulation. These findings deepen our understanding of sensory tricks in dystonia and their neurophysiological basis, providing insights that could inform therapeutic strategies such as occupational therapy or biofeedback tailored to patients' self-discovered techniques for managing dystonia.