This morning I woke up with a sore throat. A mild sore throat caused by a viral infection is uncomfortable when swallowing, making you aware how often you swallow through the day. But it does not limit the efficiency or safety of swallowing food and liquid as in swallowing disorders. Parkinson’s disease (PD) is one of the well-known causes of swallowing disorders also called ‘dysphagia’. Dysphagia can lead to less eating and drinking or aspiration of food and liquid resulting in coughing or near choking. That is why some researchers and clinicians advocate early screening of dysphagia in people with Parkinson’s disease (PwP). But how frequently does dysphagia occur in Parkinson’s disease and what are typical signs of dysphagia in PD?

Some years ago our team investigated the prevalence of swallowing disorders in Parkinson’s disease by reviewing the literature [1]. We found that swallowing disorders become more prevalent with the increase of disease severity, which is not a surprise. We also calculated a large difference between prevalence rates depending on the techniques used to identify dysphagia. Studies that used a single question to identify a swallowing problem like “Have you experienced difficulty with swallowing food or drink or a problem with choking?” generated an overall prevalence of about a third. In contrast, studies that used swallowing tests to assess swallowing capacity showed that more than 80% of PwP have a swallowing disorder. Then what is the truth? Do PwP underestimate their swallowing or do tests overestimate a swallowing disorder? Or do we need to rephrase it: When using sensitive swallowing tests 20% of PwP swallow normally, but when PwP judge their swallowing two-third consider their swallowing as functional, despite slowness of eating and drinking. One example of the latter is a PwP who recently visited our center because of multiple issues including unwanted weight loss. I saw her for a swallowing assessment, but she responded that she could eat and drink satisfactorily and without coughing. As part of the assessment she showed me how she managed to eat a regular lunch. She was clearly more hyperkinetic than hypokinetic during eating and drinking, but her chewing and swallowing were indeed functional and safe.    

A better understanding of under- or overestimation requires both PwP’s subjective judgement and objective instrumental evaluation assessed within the same patients. This summer a study with 119 PwP was published comparing patients’ responses on the single question “Have you experienced difficulty with swallowing food or drink or a problem with choking?” with a detailed endoscopic assessment of swallowing [2]. While 73% of patients denied having difficulty with swallowing, only 5% showed endoscopically complete normal swallowing. Interestingly, aspiration of liquid was the smallest problem (24%) and more over-reported (56%) than under-reported (16%) by PwP. Conversely, residue of food in the throat after swallowing was the biggest problem seen in 91% of patients, while 93% of these had responded ‘No’ to the single question. When food is not properly ‘squeezed’ through the throat, parts may stay behind, but this is seemingly not felt as prominent as coughing when aspirating. In fact, this is characteristic for PD: less squeezing can be explained by pharyngeal hypokinesia and rigidity, while being unaware of food residue in the throat may be the same mechanism that initially reduces awareness of e.g. a soft voice or stooped posture.

Then is early screening for dysphagia in PD needed? There are several points of view depending on the disease severity and availability of services. Routinely asking about difficulties with swallowing is a good start, in particular in advanced PD, but more detailed questioning may uncover possible dysphagia more reliably than a single question. Most importantly, PwP should be aware that also difficulty with chewing or swallowing is usually caused by their Parkinson’s, but can be treated or compensated quite well [3].

Links:

[1] Prevalence of Oropharyngeal Dysphagia in Parkinson's Disease: A Meta-analysis

[2] Critical Dysphagia is Common in Parkinson Disease and Occurs Even in Early Stages: A Prospective Cohort Study

[3] Hanneke Kalf explaining swallowing disorders in Parkinson’s disease for patients and caregivers

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Hanneke Kalf, PhD, SLP-CCC is a program committee member for the 5th World Parkinson Congress. She presented at WPC 2016. Dr. Kalf works as a speech-swallow therapist, clinical epidemiologist, assistant professor and lecturer at the department of Rehabilitation of the Radboud University Medical Centre in Nijmegen, the Netherlands. 

Ideas and opinions expressed in this post reflect that of the authors solely. They do not reflect the opinions or positions of the World Parkinson Coalition®