Radiation of salivary glands to reduce drooling in patients with Parkinson: a double-blind RCT

Abstract

Drooling is a common symptom in patients with Parkinson’s disease causing physical and emotional distress. It is unknown which major salivary glands are the best candidates for irradiation to reduce drooling with minimal adverse events. Therefore, this study assessed the efficacy and safety of submandibular and parotid salivary gland irradiation to reduce drooling. Patients with parkinsonism and severe drooling according to the Unified Parkinson Disease Rating Scale (UPDRS) were asked to join a prospective, randomized, double-blind, placebo-controlled trial assessing the effect of salivary gland irradiation on drooling. Exclusion criteria were use of anticholinergic drugs, salivary gland diseases, and a history of (pre)malignancy. After obtaining informed consent, patients were randomized for parotid irradiation, submandibular- and sham irradiation (2x6 Gy with one-week interval). After 6 months, sham irradiated patients were actively irradiated. Patients were evaluated at 1, 3, 6, and 12 months after radiation. Primary outcome was drooling severity according to UPDRS. Secondary outcomes were effects on stimulated glandular salivary secretion rates and adverse effects (e.g. xerostomia and sticky saliva). Between October 13, 2010 and October 28, 2015, 31 eligible patients could be included. Eleven patients were radiated on the parotid glands, 10 patients on the submandibular glands and 10 patients were sham irradiated. One patient irradiated on the parotid glands discontinued participation after three months due to physical deterioration. At six months, irradiation of parotid or submandibular glands significantly reduced drooling subjectively according to UPDRS (p < 0.001 and p = 0.011) compared to placebo treatment. Parotid and submandibular irradiation also significantly decreased salivary secretion rates equally effective, but more patients irradiated on submandibular glands experienced sticky saliva (at six months: 33% vs. 13%). Major salivary glands irradiation reduces drooling in patients with Parkinson’s disease. Parotid gland irradiation is accompanied by fewer side effects and thus preferred.