Swallowing problems should be monitored early in Huntington’s
Study finds difficulties start in initial stages of disease, progress over time
Swallowing difficulties start in the early stages of Huntington’s disease (HD) and progress over time, affecting both voluntary movements in the mouth and involuntary movements that transport food to the stomach while protecting the airway, a study showed.
Researchers used the Swallowing Disturbance Questionnaire (SDQ) to assess swallowing problems, and the Huntington’s Disease Integrated Staging System (HD-ISS) to classify the disease’s stage.
The SDQ has been tested in other brain diseases, but has rarely been used in people with Huntington’s, and the HD-ISS is a relatively recent system that covers the entire disease course, from no signs or symptoms to obvious symptoms and functional decline.
“To our knowledge, this is the first … study to specifically evaluate the SDQ across the spectrum of HD-ISS stages in a well-characterized [group] of HD gene-positive individuals,” researchers wrote.  “These findings suggest that early assessment of swallowing function is warranted in HD [Huntington’s disease] clinical care.”
The study, “Dysphagia in Huntington’s Disease: An Evaluation of Swallowing Disturbance across the HD-ISS Staging Spectrum,” was published in Movement Disorders Clinical Practice.
Team aimed to develop an HD-specific severity rating for questionnaire
Huntington’s is a progressive neurodegenerative disease that affects cognitive function, behavior, and movements, including those involved in swallowing. Swallowing difficulties, or dysphagia, make it difficult for patients to eat and drink safely, increasing the risk of choking, weight loss, and lung infections from food or liquid entering the airways.
“Swallowing impairment has been documented in HD patients across manifest disease stages, with one study reporting prevalence rates ranging from 35% in early stages to 100% in advanced stages using Dysphagia Outcome Severity Scale (DOSS),” the researchers wrote. “However, comprehensive characterization of dysphagia across the full HD disease spectrum remains limited.”
With this in mind, the researchers used the HD-ISS and SDQ to understand when dysphagia begins and how it progresses in Huntington’s across the full spectrum of the disease.
The HD-ISS classifies people carrying a disease-causing mutation into one of four stages. People not yet showing signs or symptoms of the disease are classified as Stage 0, those with a disease-specific biomarker of neurodegeneration are said to be in Stage 1, people with neurodegeneration biomarkers and motor or cognitive symptoms are classified as Stage 2, and those also showing a decline in functional ability are said to be in Stage 3.
The SDQ asks patients about symptoms related to eating and drinking. SDQ scores range from 0 to 44.5, with higher scores indicating worse dysphagia.
“Existing reports exploring swallowing disturbance in HD with the SDQ have often employed a cut-point of 11 derived from the [Parkinson’s disease] and [multiple sclerosis] literature to classify an HD subject as having dysphagia,” the researchers wrote.
For this study, the team also aimed to develop an HD-specific severity rating for the SDQ.
Each stage showed worse swallowing problems than the stage before it
The study included 87 adults diagnosed with Huntington’s: 27 in Stages 0/1, 21 in Stage 2, and 39 in Stage 3. All were followed at the University of California, San Diego’s Huntington’s Disease Society of America Center of Excellence.
Patients in the early stages of the disease were significantly younger. As the disease progressed, mouth and tongue movements, including speaking and sticking out of the tongue, became more difficult.
Many patients (39.1%) reported clinically significant difficulty with swallowing, as shown by a total SDQ score equal to or higher than 11. Dysphagia was also reported by patients in the earlier disease stages: one (3.7%) in Stages 0/1 and 10 (47.6%) in Stage 2.
The team then defined a score of 0-6 as mild dysphagia, 7-14 as moderate dysphagia, and over 14 as severe dysphagia.
Using these cut points, they found that among Stage 0/1 participants, 92.6% reported mild dysphagia and 7.4% reported moderate swallowing difficulties. Severe dysphagia was reported by nearly a quarter of Stage 2 participants (23.9%) and by nearly half in Stage 3 participants.
Overall dysphagia worsened as Huntington’s progressed. Each stage showed worse swallowing difficulties than the stage before it, with especially large differences between Stages 0/1 and Stage 3.
We found that swallowing disturbance is an early feature of HD, often manifesting even prior to a formal motor diagnosis, and that swallowing difficulties only increase with each subsequent HD stage.
Problems were found in both the oral phase (moving food in the mouth) and the pharyngeal phase (moving food down the throat to the stomach while preventing entry into the airway).
Worse dysphagia was also significantly associated with worse overall motor function, chorea (involuntary movements), and dysarthria (speech difficulties), as assessed with several validated measures.
This study showed that swallowing difficulties start early in Huntington’s and steadily worsen as the disease progresses.
“This early, concurrent involvement of both oral and pharyngeal phases might reflect the initial impact of neurodegeneration on the motor systems that coordinate swallowing,” the researchers wrote.
These results highlight the importance of monitoring swallowing from early on in the disease, so that supportive treatments can be started before complications arise.
“We found that swallowing disturbance is an early feature of HD, often manifesting even prior to a formal motor diagnosis, and that swallowing difficulties only increase with each subsequent HD stage,” the researchers wrote.
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