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

[BACKGROUND] 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.

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

[METHODS] 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.

[RESULTS] 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.

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