Abstract
Drooling can present in patients with Parkinson’s disease (PD), and it is manifested as an excessive pooling of saliva inside the oral cavity. Currently, the exact pathophysiological mechanism of drooling in PD is not yet fully explicated. Thus, it becomes crucial to understand if some clinical characteristics may emphasize drooling or if they are just concomitant. In PD, excessive drooling has been associated with a higher burden of non-motor symptoms, such as cognitive impairment, sleep problems, autonomic dysfunction, constipation and orthostatic hypotension, and of worse severity of motor fluctuations and bradykinesia. PD patients with excessive drooling also showed a reduction of striatal DAT availability at DaTSCAN imaging. Excessive drooling in patients with Parkinson’s cannot be attributed to a single factor but to a mixture of factors, including but not limited to impaired nigrostriatal pathways.
Highlights
Drooling is commonly manifested among patients with Parkinson’s disease, and it can be caused by the excess production of saliva, inability to retain saliva within the mouth, or problems with swallowing [1]
As drooling is mainly a result of a decreased frequency of saliva clearance inside the oral cavity, problems with posture [5], and oral motors, as well as facial impairment [31], it is considered that all these deficits are more common and severe as the disease progresses
These results can be attributed to the fact that non-dominant tremor patients exhibit a higher decrease in grey matter and neural functional connectivity related to motor regions [55], as well as an extensive Lewy bodies pathology in the cortical areas [56]
Summary
Drooling is commonly manifested among patients with Parkinson’s disease, and it can be caused by the excess production of saliva, inability to retain saliva within the mouth (incontinence of saliva), or problems with swallowing (dysphagia) [1]. Research studies have examined the pathophysiology of drooling in PD [2–16] in order to better understand the relationship between drooling and the clinical symptoms in PD. Neuroimaging research studies have suggested that de novo PD patients present with reduced functional connectivity in putamen, indicating that drooling is a symptom of a widespread pathology [38], which is challenging to treat [2]. Future research should further examine the relationship between drooling and other aspects of the PD symptomatology [39,40], as well as the influence of other treatments commonly used in PD and to analyze their consequences on drooling [41]
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