Clinical features associated with drooling in Parkinson's disease

Drooling is characterized by an excessive pooling of saliva in the oral cavity. The exact pathophysiological mechanism of drooling in Parkinson's disease (PD) is not yet fully understood.

To identify the relationship between drooling and other clinical features in people diagnosed with PD.

Research on the topic was carried out on the PubMed and ScienceDirect electronic databases. Articles published between March 2015 and March 2020 were selected. Search terms and inclusion and exclusion criteria were previously defined. The articles included met those requirements.

Sixteen articles were included for analysis. The prevalence of drooling varies between 9.26 and 70% and can occur at any stage of the disease. Higher prevalence of drooling is related to disease duration, disease severity, older age, male, levodopa equivalent dose, hypomimia, dysphagia, dysarthria, cognition, sleep, non-dominant tremor, motor fluctuations, bradykinesia, more symmetric pattern, gastrointestinal and urinary problems, sexual dysfunction, obstipation, and orthostatic hypotension. However, it is not related to hallucinations, rapid eye movement sleep behavior disorder, akinetic-rigid PD, mixed, nor dyskinesias.

Drooling is not caused by a single factor; it is influenced and related to several clinical features. Some clinical factors participate in the onset of drooling while others are concomitant.