“The future is bright,” stated Dr James Beck, PhD, Vice President of Scientific Affairs at the Parkinson’s Disease Foundation (www.Parkinson.org) in a Parkinson.org article about what was new in Parkinson’s research. Beck shared his excitement about the latest research on the alpha-synuclein protein that seems to abnormally clump together in the brains of people who develop Parkinson’s Disease (PD). He also mentioned how researchers are listening to the community of people with Parkinson’s to address aspects of the disease that affect daily lives (i.e., fatigue, cognitive impairments, hallucinations, dystonia, dyskinesia, and constipation). While all of these targeted aspects are critical, there was no mention of the ability to feed yourself independently, swallow safely, maintain a good quality of life around eating and drinking, and prevent adverse consequences if difficulties arise with swallowing.
Hence the mission of the Dysphagia Research Society (DRS) and our annual meetings:
Advancing the Science of Swallowing.
In this blog, I will highlight 6 exciting areas of research in Parkinson’s Disease and swallowing from the Dysphagia Research Society’s 2016 Annual Meeting, February 24-27, Tucson, Arizona. (Please also refer back to my first edition of DRS Digest: News from Dysphagia Research Society 2016, for a review of the session by Scholten and team on saliva swallowing frequency and drooling in patients with Parkinson’s Disease.)
1. Better Screening is Urgently Needed to Detect Swallowing Problems Related to Parkinson’s Disease
As noted by Erin Yeates and her team from the University Health Network in Toronto, which included Dr Rosemary Martino, “dysphagia prevalence in persons with Parkinson’s Disease (PD) vary from 30-82%, with subjective self-reports capturing lower estimates than clinician testing.” Yeates, E., Mistry, C. Cuglietta, L, Marras, C. & Martino, R presented a poster titled: “Screening for Dysphagia in People with Parkinson’s Disease: A Systematic Review.”
In an extensive literature review, they found few articles that addressed screening dysphagia in adults with PD. Only one of these screens incorporated clinician testing. They highlighted the “urgent need” for a valid screening test which includes both patient report and clinical assessment with sensitivity to detect dysphagia at early stages. If the swallowing problem is “left undetected,” it “increases the risk of aspiration pneumonia and even death,” per Yeates and team.
This urgent need is underscored when reviewing the scales that have been used to rate the severity of Parkinson’s. These scales underrepresent the issues of speech, voice and swallowing.
The older Hoehn & Yahr Scale of the five stages of PD does not directly address swallowing at all. See this article that discusses the problems with this rating scale.
The Unified Parkinson’s Disease Rating Scale (UPDRS) is newer, and it was reworked by the Movement Disorder Society (MDS-Sponsored UPDRS Revision: MDS-UPDRS). See the article by Dr Goetz about the MDS’s new revisions..
A major issue with the MDS-UPDRS, is that the SPEECH section lumps speech and voice issues together, even when the examiner is asked to make the rating. It does not separately rate specific aspects of dysarthria (i.e., articulation, resonance, phonation, and respiration/breath support). These issues are directly linked with person’s swallowing function and safety.
See full publication regarding MDS-UPDRS with the revised scale at the end of the article: pubmed link to Goetz, et al. (2008).
This new and improved MDS-UPDRS rating scale only covers swallowing under patient and caregiver reporting section, and not additionally via examiner rating (as recommended by Yeates and team above). According to the MDS-UPDRS scale under Part II, the patient would indicate a “slight” problem chewing and swallowing if he is “aware of slowness in my chewing or increased effort at swallowing, but I do not choke or need to have my food specially prepared (Goetz, et al., 2008, p 2151).” The patient may indeed have a more significant oropharyngeal dysphagia per instrumental testing, but the patient’s sensitivity to this deficit may be drastically reduced. Will that patient with a rating of only “slight” even be referred by the physician to a Speech-Language Pathologist for further testing?
The MDS-UPDRS scale assumes the swallowing difficulty is due to motor dysfunction only, and it assumes that the patient will detect his/her increased effort to swallow. However, new research suggests that person may recruit less effort to swallow, thereby not realizing that they are having a hard time swallowing.
2. Pharyngeal Motor Variability In People with Early Parkinson’s Disease
Corinne Jones, Michelle Ciucci and Timothy McCulloch from the University of Wisconsin-Madison presented research titled: “Volume-Dependent Swallowing Pressure Variability in Patients with Parkinson Disease and Healthy Controls.” They used High-Resolution Pharyngeal Manometry to measure pharyngeal and UES pressures while participants swallowed small 2cc boluses and larger 10cc boluses. (Corinne Jones was the second place winner of the DRS New Investigator Award for this research.)
Jones and team hope that research can delineate early signs of swallowing problems in people with Parkinson’s. This will help physicians and clinicians to be more proactive with evaluations and treatments. They did find a characteristic that may identify people with Parkinson’s: the idea of motor variability in a repeated task. They explained, “motor control literature associates increased effort with decreased variability.” They found that people with PD have increased variability in velopharyngeal, tongue base and hypopharyngeal pressures. They speculated that the patients may not be weak early on, but this motor variability may indicate that they may be swallowing with less recruitment of muscular effort. This may be what causes some of the dysfunction.
Interestingly, they also found that all participants (even healthy controls) showed more variability in pharyngeal and UES pressures with the smaller 2cc bolus. They concluded that at the level of the UES especially, the greater the volume the less variability.
In my opinion, this further emphasizes the need to test larger volumes, up to 20 cc as tolerated, to better define the level of impairment.
Corinne Jones commented on the teams’ future plans for PD research: “We hope to understand more about how subtle changes to swallowing function relate to other cranial and limb motor deficits seen early in the progression of the disease.”
3. Blunted Urge-to-Cough
Some background first:
Last year, Michelle Troche, PhD, CCC-SLP, from the Teachers College, Columbia University, NY, gave a tutorial on cough, and how SLPs can evaluate and rehabilitate cough deficits or dystussia on DysphagiaCafe.com. (See blog and reference list on DysphagiaCafe.com.)
In that blog, Troche cited her work (pubmed link to Troche, et al., 2014) regarding the findings “that people with PD not only have a reduced cough sensitivity, but also have a blunted perception of cough stimuli (i.e., reduced urge-to-cough).” Troche recommended to ask patients during the instrumental exam to rate their perceived urge-to-cough. The clinician can then compare the patient’s sensation with the evidence of penetration and/or aspiration on the examination.
In addition to Dr Troche’s publication linked above, please see the following publications for more background:
- Another publication by Troche, et al., 2014 to better understand mechanisms of cough and airway protection.
At DRS2016, Michelle Troche, Alexandra Brandimore, Beate Schumann and Karen Hegland presented a poster titled: “Clinical Predictors of Airway Protective Dysfunction in Parkinson’s Disease.” Troche and team won 3rd place for this poster presentation. As they noted in their work, “It is important to identify the factors that influence airway protective outcomes in PD, because aspiration pneumonia is a leading cause of death.”
These researchers hope to uncover disease-specific and airway protective factors in PD that could predict the safety of a person’s swallowing function. Swallowing safety was judged by the participants’ Penetration/Aspiration Scale scores. They found significant sensitivity and specificity with the following factors:
Disease duration identified patients with normal versus abnormal safety.
Reflexive cough (not voluntary cough) identified patients who had more severe penetration/aspiration.
Urge-to-cough was the best predictor to differentiate patients who penetrate only versus those who aspirate.
4. Airway Sensation is Also Blunted
Karen Hegland, Alexandra Brandimore and Michelle Troche shared their findings in a poster titled: “Airway Sensation is Blunted in Adults with Parkinson’s Disease Compared to Age-Matched Older Adults.” Hegland noted that there is a “blunted urge-to-cough” in people who have dysphagia related to PD. Researchers are finding that this is actually a deficit in respiratory sensation.
Hegland and team tested respiratory sensation by delivering resistive breathing loads as subjects inhaled. Participants with Parkinson’s did not perceive as great of a difficulty in breathing as did the age-matched older adults. The researchers note that this blunted respiratory sensation may cause an airway protective dysfunction.
5. Good News: You Can Train an Improved Cough and Airway Protection
Two sessions addressed intensive therapy:
1) Alexandra Brandimore, Karen Hegland and Michelle Troche presented on: “Volitional Up-Regulation of Reflex and Voluntary Cough in Health Older Adults and Parkinson’s Disease.” Alexandra Brandimore, PhD, CCC-SLP from the Teachers College, Columbia University, Gainesville, FL, received a 3rd place award for her oral presentation.
Brandimore noted how dystussia is a sensory and motor deficit.
These researchers studied the reflexive (stimulated with capsaicin) and voluntary sequential coughs. To “up-regulate cough airflow,” the patients were trained to reach a visual target while being verbally cued to “cough hard.” Airflow measurements were obtained (similar to the measurements described in the cough tutorial on DysphagiaCafe): Inspiratory Volume (IV), Compression Phase Duration (CPD), Cough Expired Volume (CEV – a measure of cough effectiveness), and Peak Expiratory Flow Rate (PEFR).
The good news: people with PD were able to improve their reflexive and voluntary cough effectiveness. Even participants with more severe PD were able to hit the visual targets. However, even though people with PD improved their peak expiratory flow rates, it was still less than healthy older adults. Brandimore noted that the people with PD have decreased cough effectiveness and initiated the cough at lower lung volumes (e.g., less Inspiratory Volume – IV). She noted that healthy older adults modified their cough by increasing their inspiratory volume and decreasing their compression phase duration (during which expiratory muscles contract and the vocal folds adduct just prior to the cough, per Troche, 2015, DysphagiaCafe). The different pattern in participants with PD may be due to chest wall rigidity and bradykinesia, per Brandimore. Brandimore concluded with noting how some participants with PD did not reliably cough in response to capsaicin, and they will look at these “non-responders” more closely.
2) Dr Michael Hammer, from the University of Wisconsin-Madison, and his lab group have focused on airway sensory deficits related to airway protection, dysphagia, dysphonia and treatments for these deficits in people with Parkinson’s Disease. See pubmed links below for a few of his publications.
His 2015 DRS presentation ties in nicely with this topic, where he addressed laryngeal mechanosensory detection and the adductor reflex. He found that individuals with Parkinson’s Disease have reduced sensory awareness, as well as impaired laryngeal protective reflexes.
Dr Hammer’s presentation at DRS2016 (“Airway Protection in Parkinson’s Disease Improves After Intensive Therapy“) included a preliminary report of improved airway sensory protective mechanisms and improved cough physiology after intensive airway exercises for individuals with Parkinson’s Disease. According to Dr Hammer, these findings highlight the importance of airway sensory mechanisms to airway protection, swallow and voice. Additionally, airway sensory deficits are associated with declines in each of these functions in Parkinson’s Disease. Publication of this work is forthcoming, but a key point to emphasize is the importance of exercise.
Dr Hammer shared that his recent work has provided encouraging insights for people with Parkinson’s Disease, and for other neurodegenerative diseases.
Dr Hammer’s publications can be downloaded for free at the US Nationally Library of Medicine (PubMed.gov). Readers are encouraged to read the primary manuscripts for more details.
- 2009 regarding device development for measuring laryngeal mechanosensory detection thresholds: https://www.ncbi.nlm.nih.gov/pubmed/19272888
6. Impaired Sensation in People with Parkinson’s Disease Includes Taste and Smell
Lucia Mourao and Daniella Lima noted how the sensory branches of the cranial nerves (CN V, VII, IX, and X) may be impaired in people with PD. Specifically, loss of sensory input from the glossopharyngeal (IX) and the vagus (X) may be contributing to dysphagia in this population. (They cited the following article regarding this issue: Mu L, Sobotka S, Chen J, et al. (2013). Parkinson Disease Affects Peripheral Sensory Nerves in the Pharynx. Journal of Neuropathology and experimental Neurology, 72 (7), 614-623.)
In their poster titled: “Modifications of Taste and Smell and the Presence of Penetration/Aspiration in Elderly Without Neurological Disorders and Parkinsonian Syndromes,” Mourao and Lima noted patients who are classified as Parkinsonian had more penetration and aspiration than healthy age-matched controls. Additionally, this impaired safety (or presence of penetration) correlated with an impaired sense of taste and smell (as categorized by the International Classification of Functioning, Disability and Health (ICF). Note: specific Parkinsonian Syndromes were not identified, and findings may not translate readily to all patients with PD.
Take-Home Messages in
Parkinson’s Disease Research
The future is bright, especially with such a broad focus of research on Parkinson’s Disease and swallowing at DRS2016.
Screening for difficulties in eating and swallowing needs to include the patient’s perceptions, caregiver reports, and examiner observations. Ratings of the severity of the disease need to include separate ratings speech, voice, feeding, chewing and swallowing dysfunction, as all these issues are factors in quality of life and prevention of adverse outcomes.
Research is helping to delineate subtle changes that occur early on in the disease to help detect swallowing disorders before an aspiration pneumonia occurs. Jones’ research will help better test for subtle deficits, such as the increased motor variability seen in the pharyngeal pressures in people with Parkinson’s. Instrumental testing should include a full array of volumes, as all participants in their study showed high motor variability with small-2cc-sized boluses.
As the disease duration progresses and there is more risk for impaired swallowing safety, meals may become a chore and less enjoyable. Factors affecting quality of life around eating may also be a decline in the senses of taste and smell, which were found to correlate with the presence of airway compromise (penetration).
It is important for physicians and clinicians to remember that people with PD may under-represent their difficulty swallowing. Your patient with Parkinson’s may not be simply minimizing the issue to dismiss further testing. Rather, the person’s mechanosensory recepters in the larynx may not detect the liquid, food or saliva as they invade the airway. His airway’s sensorimotor control may not respond quickly and robustly with a reflexive clearing cough. The respiratory sensation may be blunted, causing a decreased perceived effort and reduced urge-to-cough. The SLP can use this evidence when advocating for further instrumental testing for our patients who have Parkinson’s Disease. Early intervention can potentially slow the sensorimotor decline, minimize adverse outcomes and maintain a high quality of life.
Therapy should not only focus on motor dysfunction, but also target these sensory and perceptual deficits to improve cough effectiveness, airway protection and potentially prevent aspiration pneumonia. We can encourage our patients to stay highly motivated, as therapy and exercise work!