Chewing Dystonia and Sensory Modulation: An Exploratory Study of Intraoral Lidocaine Effects

Chewing dystonia is a rare, task-specific oromandibular dystonia that causes involuntary jaw and tongue movements during mastication and often refractory to standard treatments for dystonia. Emerging evidence suggests that peripheral sensory modulation may play a role in dystonia pathophysiology, but this has not been systematically evaluated as potential treatment modality.

The aim of this study was to explore the therapeutic and neurophysiological effects of intraoral topical lidocaine in patients with task-specific chewing dystonia.

This prospectively documented exploratory case series included 6 patients (4 Yemeni males, 2 Indian females), with chewing dystonia unresponsive to medications or botulinum toxin. Two cases were previously reported; 4 were subsequently documented using a uniform clinical protocol. Unified Dystonia Rating Scale (UDRS) scores were assessed before and after intraoral lidocaine during chewing of hard and soft foods. All patients were video recorded; 3 underwent electromyography (EMG). Burst duration and root mean square amplitude were analyzed. Wilcoxon signed-rank tests assessed significance.

Mean UDRS scores improved significantly for both hard-consistency foods (7.17 ± 0.75 to 3.83 ± 0.69; P = 0.031) and soft-consistency foods (4.6 ± 0.62 to 2.25 ± 0.96; P = 0.031). Inter-rater reliability was high. EMG data showed reductions in root mean square (RMS) amplitude ranging between 18.6% and 36.5% across 3 patients alongside visual shortening of burst durations. Symptom relief occurred within minutes, lasted 60-90 minutes, and was observed across both balm and spray formulations without adverse effects.

Intraoral lidocaine may provide rapid, noninvasive relief in task-specific chewing dystonia. These findings support further investigation into sensory-based therapeutic approaches.