Drooling in Parkinson's disease: a review

Abstract

Parkinson's disease (PD) is a neurodegenerative disease causing both motor and non-motor symptoms. Drooling, an excessive pooling and spillover of saliva out of the oral cavity, is one of the non-motor symptoms in PD patients that produces various negative physical and psychosocial consequences for patients and their caregivers. At present, the pathophysiology of drooling in PD is not completely certain; however, impaired intra-oral salivary clearance is likely the major contributor. There are neither standard diagnostic criteria nor standard severity assessment tools for evaluating drooling in PD. In accordance with the possible pathophysiology, dopaminergic agents have been used to improve salivary clearance; however, these agents are not completely effective in controlling drooling. Various pharmacological and non-pharmacological treatment options have been studied. Local injection with botulinum toxin serotypes A and B into major salivary glands is most effective to reduce drooling. Future research to explore the exact pathophysiology and develop standard diagnostic criteria and standard severity assessment tools are needed to formulate specific treatment options and improve patient care.

Keywords: Botulinum toxin; Drooling; Parkinson's disease; Sialorrhea.

Figure 1

Possible pathophysiology of drooling in Parkinson's disease

Figure 2. Landmark for injecting parotid and submandibular gland

(A) Parotid gland: Drawing the imaginary line starts from the tragus to angle of the mandible; then the mid-point of this line is the landmark for injecting botulinum neurotoxin into the gland. (B) Submandibular gland: Drawing the imaginary line, along with the length of body of the mandible, starts from angle of the mandible to tip of the chin; then one finger breadth medial to the mid-point of this line is the landmark for injecting botulinum neurotoxin into the glands.