Mastication problems in patients with spinal muscular atrophy (SMA) types 2 and 3 are characterized by inefficiency, reduced endurance, and fatigue, according to a new study published in Dysphagia. However, not all patients are aware of their mastication problems.

Mastication problems can negatively impact food intake and reduce quality of life. Patients with SMA often report mastication problems, and it is well known that the disease affects maximal mouth opening. However, how the disease affects more complex functions such as chewing is unclear, as are the prevalence and severity of mastication problems in SMA.

Here, a team of researchers from the Netherlands conducted a cross-sectional study to characterize mastication problems and understand their nature and underlying mechanisms in patients with SMA type 2 or 3 with self-reported bulbar problems.

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The study included 18 patients with SMA type 2 and 9 patients with SMA type 3; 3 of these 9 patients were still ambulatory. The researchers assessed mastication using a questionnaire, clinical mastication tests, and ultrasound of the mastication muscles.

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The results showed that nonambulatory patients reported problems in at least 1 of 3 items in the questionnaire: “biting off hard food,” “difficulty with chewing,” and “fatigue while chewing.” They also required more masticatory cycles, swallows, and time to finish a cracker than healthy people. Finally, patients with SMA experienced increased pain and fatigue directly after the 6-minute mastication test and 5 minutes after they completed the test, compared to healthy people. The mastication problems were associated with reduced maximal mouth opening.

In order to investigate abnormalities in bulbar muscle groups that may be associated with mastication problems, the researchers performed mastication muscle ultrasounds. The results of these showed an abnormal muscle structure in 90% of all patients, regardless of whether they were still able to walk.

“Mastication problems in patients with SMA types 2 and 3 are characterized by inefficiency, reduced endurance, and fatigue, probably caused by masticatory muscle changes that can be detected by ultrasound,” the researchers concluded. 

They added that a combination of quantitative and qualitative mastication tests should be used in addition to a questionnaire to assess masticatory function in patients with SMA.


Van der Heul AMB, van Eijk RPA, Wadman RI, et al. Mastication in patients with spinal muscular atrophy types 2 and 3 is characterized by abnormal efficiency, reduced endurance, and fatigue. Dysphagia. Published online August 15, 2021. doi:10.1007/s00455-021-10351-y