DMDDuchenne muscular dystrophy LSCM Left sternocleidomastoid muscle RSCM Right sternocleidomastoid muscle AIM This study aimed to analyse electromyographic activity, masticatory efficiency, muscle thickness, and bite force of individuals with Duchenne muscular dystrophy (DMD).METHOD Forty males aged 4-15 years, 20 with DMD and 20 healthy age-, height-, and weight-matched controls, underwent electromyography and ultrasonography of temporalis, masseter, and sternocleidomastoid muscles during postural control of the jaw, mastication, and maximal molar bite force.
RESULTSThe normalized electromyography signals showed higher activity in masseter and temporal muscles at rest, during protrusion, left and right laterality, and fatigue condition in the group with DMD than in the comparison group (p≤0.05). For masticatory efficiency of cycles, in analysis of non-habitual chewing of flavourless gum, and habitual chewing of peanuts and raisins, the group with DMD presented lower averages (p≤0.05). For the muscle thickness, the results showed that there was a lower muscle thickness in the group with DMD for all muscles during the rest and maximal voluntary contraction, except for masseter and sternocleidomastoid in the maximal voluntary contraction. In the maximal molar bite force, the group with DMD presented higher values for both sides than the comparison group (p≤0.05).INTERPRETATION Patients with DMD show muscle changes related to the stomatognathic system, in their activity, bite force, and muscle thickness.Duchenne muscular dystrophy (DMD) is an X-linked lethal neuromuscular disease that affects males. 1,2 Necrosis of skeletal muscle fibres, muscle fibrosis, and the infiltration of adipose tissue are seen from infancy. 3,4 Diagnosis is based on clinical presentation associated with a DNA diagnosis, significant elevations in the serum creatine kinase levels, morphological changes in the affected muscles, and the absence of the protein dystrophin. 5,6 The primary consequence of DMD is the decline of muscle function. Surface electromyography (EMG) has great potential as a measurement instrument in assessing muscle biomechanics.7 Quantitative EMG data can provide information on disease severity in various muscular dysfunctions. 8 The concomitant use of ultrasonography allows for the observation of changes in the muscle architecture, with the substitution of muscle cells by fat and connective tissue. The purpose of this study was to use surface EMG to detect changes in the patterns of EMG signals in patients with DMD to assess the activity of their temporalis, masseter, and sternocleidomastoid muscles bilaterally, and to analyse the masticatory efficiency, maximal molar bite force, and ultrasonography to evaluate muscle thickness of these muscles.These methods of analysis allow for the functional and quantitative study of the muscular system and provide important information about the morphology and activity levels of the muscles.10 Information about alterations in muscles of the stomatognathic system, including bite force...