Caractérisation des déficiences musculaires et des limitations d’activités liées à la mobilité intérieure chez une population atteinte de dystrophie musculaire oculopharyngée (DMOP)

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant (in most cases), progressive genetic disease. In Quebec, it has one of the highest prevalences in the world (1/1000). A mutation in the gene encoding Poly(A) Binding Protein Nuclear 1 (PABPN1) causes an abnormal number of repetitions of the nucleotide triplet (GCN). This leads to ptosis (drooping eyelids), dysphagia (difficulty swallowing), and proximal muscle weakness. These impairments typically appear in the fifties and worsen over time. They can result in several impacts, including limitations in activities related to indoor mobility. However, studies on muscular impairments and limitations in activities related to indoor mobility remain scarce to date. A scoping review was conducted using the JBI methodology, including 54 studies. The results indicate a divergence in the methodology used, which prevents the establishment of clear conclusions regarding the prevalence and severity of muscle impairments. Among the studies assessing mobility-related activity limitations, only two prospective studies were identified and two studies used reference values to assess the severity of muscle or mobility impairments. Furthermore, no studies addressed the explanatory factors of these activity limitations, although such studies are necessary to guide clinicians for the management and rehabilitation of OPMD. These results allowed the conceptualization of a study with a cross-sectional descriptive design with the objectives of documenting: 1) the lower limb muscle strength and activities related to indoor mobility, and 2) the explanatory factors of activity limitations related to indoor mobility in people with OPMD. 113 symptomatic participants aged between 40 and 74 years, with a genetic or clinical diagnosis of OPMD, and from four neuromuscular clinics in Canada, were evaluated. The evaluation protocol included maximal isometric muscle strength of five lower limb muscle groups, balance, and activities related to indoor mobility. Results show that lower limb muscle strength ranged from 41.4% to 76.4% of reference values, with hip flexors being the weakest among the five muscle groups. The 10-meter walk test at self-selected and maximal speed, the 30-second sit-to-stand test, and the 10-step test (maximum ascent and descent) ranged from 44.9% to 83.3% of reference values. Across all regression models, balance (BERG scale), balance confidence (Activities-specific Balance Confidence Scale), and the strength one of the lower limb muscle groups were significant explanatory factors for each clinical assessment tool related to indoor mobility. All models explained between 50.4% and 80.5% of the variance (adjusted R2) of the performance obtained on the clinical assessment tools. This is the first study to document the explanatory factors of limitations in indoor mobility in OPMD, demonstrating the importance of targeting muscle strength and balance for rehabilitation.

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