Commonly used clinical scales to measure symptom severity in myasthenia gravis (MG) patients are insufficient to precisely evaluate swallowing problems and predict the risk of silent aspiration, a study reports.
Patients with difficulty swallowing and disease severity classified as IIb/IIIb (MGFA clinical classification) need appropriate therapeutic management regardless of how they score on other clinical scales. Neurological exams should be accompanied by swallowing-specific exams such as endoscopy in those at high risk of silent aspiration, the study’s authors stated.
The study, “Assessment of oropharyngeal swallowing dysfunction in myasthenia gravis patients presenting with difficulty in swallowing” was published in the journal Auris Nasus Larynx.
Certain conditions, such as MG, can weaken a person’s throat muscles, making it difficult to swallow food, a condition referred to as dysphagia. Studies estimate that about 70 percent of people with MG have some sort of swallowing problem, but the severity varies among patients.
Both the oral and pharyngeal phases of swallowing are frequently disturbed in MG patients — a condition called oropharyngeal dysphagia, meaning a difficulty in moving food from the mouth into the throat and esophagus.
This is one of the most serious symptoms of MG, as it may lead to silent aspiration of food or fluids into the airways and introduce bacteria into the lungs, causing pneumonia. Yet the best way to grade dysphagia or predict the risk of aspiration in MG is still unclear.
While it has been reported that clinical neurological examinations are not sufficient, a more effective approach may be to combine neurological assessments with swallowing exams.
A team of researchers at Japan’s Graduate School of Medicine, Kumamoto University conducted a study to test this hypothesis.
They examined a group of 13 MG patients with dysphagia without aspiration combining swallowing exams, including videofluorographic and fiber-optic endoscopy, with MG neurological symptom severity, measured with the Myasthenia Gravis Foundation of America (MGFA) clinical classification, the MG Activities of Daily Living (MG-ADL) score, and the Quantitative Myasthenia Gravis (QMG) test score.
The swallowing studies revealed that dysphagia was more severe in patients who had more severe neurological symptoms measured by MGFA classification.
Specifically, those with IIb/IIIb disease (mild to moderate weakness predominantly in oropharyngeal muscles) had greater impairments in swallowing than those with IIa/IIIa disease (mild to moderate weakness predominantly in limb, axial muscles or both).
However, none of the swallowing assessments correlated significantly with the MGADL and QMG scores.
Of all the parameters measured by the clinical scales, only hand grip (QMG score) was highly correlated with the severity of dysphagia — the poorer a patient’s hand grip, the greater the swallowing problems.
Researchers emphasize that although patients with MGFA IIb/IIIb disease did not present with aspiration, they had severely impaired pharyngeal muscles.
“Therefore, the swallowing dysfunction in these patients, specifically the reduced pharyngeal clearance, must be managed.” they stated. Also, MGFA classification is not an objective method and alone “would fail to precisely evaluate swallowing dysfunction in MG patients.”
The results “should alert neurologists to the risk of silent aspiration, even in patients diagnosed with clinically and neurologically mild MG according to the QMG and MG-ADL scores,” researchers said.
To screen for the risk of aspiration in MG patients, neurologists may use a self-directed questionnaire and consider the grip score, regardless of the overall results on QMG and MG-ADL scales, the team said.
Patients identified as being at high risk of aspiration should then undergo a detailed swallowing examination, such as an endoscopy, with an otolaryngologist.
In the future, prospective studies that include more patients, age-matched controls and assessment of the diversity of dysphagia patterns are needed, they stated.