ALS May Have Negative Affect on Muscles Necessary for Chewing, Study Finds

Patients with amyotrophic lateral sclerosis (ALS) show alterations in the activity of their masticatory (jaw) muscles, impairing their ability to chew, according to the results of a small study.

The study, “Alterations in the stomatognathic system due to amyotrophic lateral sclerosis,” was published in the Journal of Applied Oral Science. 

The effect of ALS on face muscles, namely those involved in mastication (chewing), is poorly chronicled in the literature. So, researchers investigated the impact of ALS in the stomatognathic system, which includes the teeth, jaws and associated soft tissues.

They analyzed the maximal molar bite force, and the electrical activity of skeletal muscles (electromyographic activity), chewing efficiency, and thickness of two muscles important in chewing, called masseter and temporalis muscles.

They screened a group of 70 patients with ALS, aged 18 to 68 years old, and followed them at the Department of Neurosciences and Behavioral Sciences, Ribeirão Preto, São Paulo, Brazil.

Of the 70 patients, 15 at the early stages of the disease were selected for the final analysis, which also included 15 healthy controls matched for age, sex, and anthropometric measurements (including height, weight, body mass index, waist-to-hip ratio, and percentage of body fat).

A single trained professional evaluated the partcipants’ electromyographic, masticatory efficiency, thickness and bite force records.

The results showed that the electrical activity of the masseter muscle was significantly increased in ALS patients at rest compared to healthy controls.

“These results are in accordance with earlier results in scientific literature wherein the presence of electrical hyperactivity in the skeletal striated muscles has been correlated to situations of continuous stress and/or the presence of muscular dysfunctions,” the researchers wrote.

The analysis also revealed greater muscular hyperactivity in the ALS group relative to controls. Additionally, the masseter muscles were more active when compared with the temporalis muscles.

The chewing efficiency of the right masseter and right temporalis muscles in individuals with ALS was significantly reduced. No differences were found in the masticatory muscle thickness and maximal molar bite force between groups.

Overal, these reults suggest that ALS can indeed impact the stomatognathic system and affect patients’ chewing abilities.

“All health professionals, especially those in the dentistry field, should carefully plan and apply adequate therapies to avoid greater damages to muscular system in individuals with ALS and the monitoring of these individuals should be effective and constant,” researchers wrote.

“Other studies should be performed in subjects with ALS in more advanced stages, allowing a better understanding of the performance of the masticatory muscles,” the study concluded.