Orofacial muscles may be affected in early stages of Becker muscular dystrophy: A preliminary study.

BACKGROUND: Dysphagia is reported in patients with Duchenne or Becker muscular dystrophy. Our clinical experience suggests that, compared with Duchenne patients, impaired mastication and swallowing occur early in Becker patients relative to their skeletal muscle involvement. The aim of this study was to assess dysphagia in Duchenne and Becker patients in relation to ambulatory capacity. METHODS: In patients in the early ambulatory stage, clinical symptoms, quantitative muscle ultrasound of the orofacial muscles, and maximum bite force were assessed. The 6-Minute Walk Test (6MWT) was used to measure ambulatory capacity. RESULTS: Eleven Duchenne and 11 Becker patients were included. Although Becker patients had a greater 6MWT distance than Duchenne patients, the occurrence of mastication and swallowing difficulties was similar. The temporalis muscle was significantly thicker in Becker patients. CONCLUSIONS: Clinicians should be aware of dysphagia in both groups, even when ambulation is still well preserved.

Association of Elbow Flexor MRI Fat Fraction With Loss of Hand-to-Mouth Movement in Patients With Duchenne Muscular Dystrophy.

BACKGROUND AND OBJECTIVES: To study the potential of quantitative MRI (qMRI) fat fraction (FF) as a biomarker in nonambulant patients with Duchenne muscular dystrophy (DMD), we assessed the additive predictive value of elbow flexor FF to age at loss of hand-to-mouth movement. METHODS: Nonambulant patients with DMD (age ≥8 years) were included. Four-point Dixon MRI scans of the right upper arm were performed at baseline and at the 12-, 18-, or 24-month follow-up. Elbow flexor FFs were determined from 5 central slices. Loss of hand-to-mouth movement was determined at study visits and by phone calls every 4 months. FFs were fitted to a sigmoidal curve by use of a mixed model with random slope to predict individual trajectories. The added predictive value of elbow flexor FF to age at loss of hand-to-mouth movement was calculated from a Cox model with the predicted FF as a time-varying covariate, yielding a hazard ratio. RESULTS: Forty-eight MRIs of 20 patients with DMD were included. The hazard ratio of a percent-point increase in elbow flexor FF for the time to loss of hand-to-mouth movement was 1.12 (95% confidence interval 1.04-1.21; p = 0.002). This corresponded to a 3.13-fold increase in the instantaneous risk of loss of hand-to-mouth movement in patients with a 10-percent points higher elbow flexor FF at any age. DISCUSSION: In this prospective study, elbow flexor FF predicted loss of hand-to-mouth movement independently of age. qMRI-measured elbow flexor FF can be used as a surrogate endpoint or stratification tool for clinical trials in nonambulant patients with DMD. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that qMRI FF of elbow flexor muscles in patients with DMD predicts loss of hand-to-mouth movement independently of age.

Fighting Against Disuse of the Masticatory System in Duchenne Muscular Dystrophy: A Pilot Study Using Chewing Gum.

Duchenne muscular dystrophy patients report masticatory problems. The aim was to determine the efficacy of mastication training in Duchenne muscular dystrophy using chewing gum for 4 weeks. In all, 17 patients and 17 healthy age-matched males participated. The masticatory performance was assessed using a mixing ability test and measuring anterior bite force before, shortly after and 1 month after the training. In the patient group the masticatory performance improved and remained after 1-month follow-up, no significant changes in anterior maximum bite force was observed after mastication training. In the healthy subject the bite force increased and remained at the 1-month follow-up; no significant differences in masticatory performance were observed. Mastication training by using sugar-free chewing gum in Duchenne muscular dystrophy patients improved their masticatory performance. Since bite force did not improve, the working mechanism of the improvement in chewing may relate to changes of the neuromuscular function and coordination, resulting in improvement of skills in performing mastication.

Biomechanical events of swallowing are determined more by bolus consistency than by age or gender.

The biomechanics of swallowing saliva and substances of different consistencies were investigated in healthy children and adults. To this end, the duration and mean amplitude value (MAV) of surface electromyography (sEMG) of the submental muscle group (SMG) activity, the maximum anterior tongue pressure (ATP), and the rise and release slopes of ATP were measured while participants (39 female and 39 male participants, age 5-65 years) swallowed saliva, 5 mL water (reference), 5 mL thick liquid, and 5 mL solid food. Mean outcome parameters varied with the consistency of the liquid or food swallowed, with the exception of the rise slope of ATP. Moreover, outcome variables were not substantially affected by age with children of 5 years and older showing similar biomechanical events to those of adults. It is important to gain insight into the biomechanics of swallowing saliva and substances of different consistencies in order to understand the underlying mechanisms of dysphagia children and adults.

Impaired mandibular function in spinal muscular atrophy type II: need for early recognition.

The aim of the study is to assess mandibular function in young patients with spinal muscular atrophy type II. A total of 12 children and young adults with spinal muscular atrophy type II and 12 healthy matched controls participated. The mandibular function impairment was moderate to severe in 50% of patients. A limited mouth opening (≤30 mm) was observed in 75% of the patients. In patients with a severe reduction of the mandibular range of motion the temporomandibular joint mainly rotated during mouth opening instead of the usual combination of rotation and sliding. The severity of the limited active mouth opening correlated with the severity of the disease (motor function measure scores). This study shows that mandibular dysfunction is common among young patients with spinal muscular atrophy type II. Early recognition of mandibular dysfunction may help to prevent complications such as aspiration as a result of chewing problems.

Is head balance a major determinant for swallowing problems in patients with spinal muscular atrophy type 2?

A child with spinal muscular atrophy type 2 was referred for evaluation of eating and swallowing problems. The dysphagia evaluation demonstrated coughing during eating and drinking and occasionally stertorous when eating solid food. The videofluoroscopic swallow study showed a late upper esophageal sphincter opening with hypopharyngeal residue, more with solid food than with thin liquid. His lumbar lordosis associated with anterior tilted pelvis and his problems with head balance due to weak neck musculature caused compensatory behavior like a retracted neck and mandible. This position negatively influences the opening of the upper esophageal sphincter. This case supported the idea that dysphagia in spinal muscular atrophy type 2 is caused by both a bulbar component as well as a treatable posture component.