Botulinum Toxin Injections for Drooling Improve Dysphagia in Patients with Parkinson’s Disease

Drooling and dysphagia are frequent and disabling complications in Parkinson's disease (PD) and often coexist, with drooling mainly resulting from impaired saliva clearance due to reduced oral motor control and potentially worsening swallowing function. This study aimed to evaluate whether botulinum toxin type A (BoNT/A) injections into the major salivary glands, beyond controlling drooling, could also improve swallowing performance using clinical and neurophysiological measures. Twenty PD patients with severe drooling and dysphagia underwent bilateral ultrasound-guided BoNT/A injections into the parotid and submandibular glands. Assessments were performed at baseline and at 1, 8, and 12 weeks post-injection. Dysphagia severity was evaluated using the Penetration-Aspiration Scale and the Dysphagia Severity Rating Scale. Neurophysiological assessment included electromyographic recordings from suprahyoid/submental and cricopharyngeal muscles, together with mechanomyography analysis of laryngeal movement during swallowing. Following BoNT/A treatment, a consistent reduction in drooling was observed, accompanied by significant improvements in clinical dysphagia scores and neurophysiological swallowing parameters across all follow-up time points. These findings suggest that incobotulinumtoxinA injections into salivary glands not only reduce drooling but also enhance swallowing function in PD patients, possibly by facilitating oral floor and oropharyngeal motor coordination secondary to improved saliva management.