Masticatory muscle function in patients with spinal muscular atrophy

The purpose of this study was to determine whether spinal muscular atrophy affects masticatory muscle strength and mandibular range of motion. A sampl e of 15 subjects with spinal muscular atrophy was compared to a sample of a ge-matched and sex-matched controls. Maximum bite force, masticatory muscle electromyography activity, mandibular ranges of motion and masticatory mus cle endurance were evaluated. Results showed that maximum bite forces were one-half as great for the sample with spinal muscular atrophy than for the controls, even though their EMG activity was not significantly different. S lopes of the relationship between electromyography activity and bite force were two to four times steeper for patients with spinal muscular atrophy th an controls. Maximum opening and protrusion were reduced to approximately o ne-half control values. Fatigue times of patients with spinal muscular atro phy were reduced by 30% (17.9 seconds versus 11.1 seconds), We conclude tha t the masticatory muscles of patients with spinal muscular atrophy are weak ened, that their muscles are less efficient, and that they fatigue more qui ckly than controls. In addition, mandibular movements of these patients tak e place over a more limited range than unaffected controls.