In Myasthenia Gravis, Standard Assessments Alone Are Insufficient to Assess Dysphagia

Regardless of how they score on the commonly used clinical scales of symptom severity, patients with myasthenia gravis (MG) are not sufficiently evaluated for swallowing problems or their risk of silent aspiration by these measurements, according to new research.¹

It has previously been reported that clinical neurological examinations are not sufficient to grade dysphagia or predict the risk of aspiration in patients with MG, but a group of researchers from the Kumamoto University Graduate School of Medicine suggested a more effective method may be to combine those exams with swallowing tests.

“Dysphagia is a frequent symptom in patients with MG, 6% to 15% of whom present with dysphagia as the first symptom of the disease,” the research team wrote. “Even among patients with mild to moderate MG (MGFA II or III), silent aspiration occurs in 35%. However, few studies have focused on the clinical characteristics of MG patients with mild swallowing dysfunction, the prediction of aspiration, or the correlation between clinical neurological presentation and swallowing dysfunction in MG.”

The study’s findings supported the team’s hypothesis, showing that those who are categorized as IIb/IIIb by the Myasthenia Gravis Foundation of American (MGFA) clinical classification and present with difficulty swallowing should be managed appropriately with therapies and, additionally, should have their neurological exams followed by swallowing-specific evaluations when at risk of silent aspiration.

MGFA Clinical Classification IIb/IIIb is defined as patients with moderate weakness affecting muscles other than ocular muscles, which can include ocular muscle weakness of any severity.2

Class IIb is defined as those whose condition is “predominantly affecting oropharyngeal, respiratory muscles, or both, and “may also have lesser or equal involvement of limb, axial muscles, or both,” while Class IIIb is defined as disease “predominantly affecting oropharyngeal, respiratory muscles, or both, which “may also have lesser or equal involvement of limb, axial muscles, or both.”

The study examined 13 patients with MG who presented with dysphagia and without aspiration, by combining videofluorographic (VF) and fiber-optic endoscopy (FE) with MG neurological symptom severity, as measured by MGFA clinical classification, the MG Activities of Daily Living (MG-ADL) score, and the Quantitative MG (QMG) test score.

The Hydo’s FEES scale and pharyngeal residue examined using VF were significantly (P <.05) more severe than in patients classified with MGFA IIa/IIIa disease. Ultimately, even though these patients arrived with dysphagia without aspiration, those with MGFA IIb/IIIb disease had severely impaired pharyngeal muscles when examined with VF, thus the researchers expressed their concern for the use of the MGFA classification as a subjective evaluation method. In the MG recommendations for clinical research standards by Jaretzki et. al, the MGFA classification is described as “designed to identify subgroups of patients with MG who share distinct clinical features or severity of disease that may indicate different prognoses or responses to therapy.”3 This, according to the Kumamoto University team, is indicative enough in itself that the MGFA classification defers quantitative assessment of muscle weakness to the Quantitative MG Score for Disease Severity.

“This evaluation alone without VF and FE would fail to precisely evaluate swallowing dysfunction in MG patients,” they wrote.

Additionally, the results suggested that neurological assessment with QMG and MG-ADL was not correlated with any parameters evaluated in the study save for the grip score within QMG assessment. And although the authors acknowledged that this may be due to the 13 patients with MG that were evaluated only had mild to moderate swallowing difficulty without aspiration, they noted suggested that these results should alert neurologists to the possible risk of silent aspiration even in patients with mild MG.

The authors acknowledged the small sample size, the absence of an age-matched control group, and the lack of an assessment of the entire spectrum of dysphagia severity with various concentration and volume of test materials as limitations of the study. They suggested a further prospective assessment to replicate the findings.

“The control of pharyngeal residue, especially in patients with MGFA IIb/IIIb disease, is essential to prevent silent aspiration. Cooperation between board-certified otolaryngologists and neurologists is indispensable for the management,” the researchers concluded.

REFERENCES

1. Kumai Y, Miyamoto T, Matsubara K, et al. Assessment of oropharyngeal swallowing dysfunction in myasthenia gravis patients presenting with difficulty in swallowing. Auris Nasus Larynx. Published online 2018. aurisnasuslarynx.com/article/S0385-8146(18)30600-X/

fulltext

. Accessed January 14, 2019.

2. MGFA Clinical Classification. MGFA website. myasthenia.org/LinkClick.aspx?fileticket=sIitErMYbkA%3d&tabid=125. Accessed January 14, 2019.

3. Jaretzki A, Barohn RJ, Ernstoff RM, et al. Myasthenia gravis: Recommendations for clinical research standards. Neurology. 2000;55(1):16-23.

doi

: 10.1212/WNL.55.1.16