Evaluation of muscle strength in patients with spinal muscular atrophy

The first aim of this study was to evaluate the muscular strength in order to document the strength scores for patients with spinal muscular atrophy (SMA). The second aim was to analyze the differences in average strength score among the musculatures at various body parts. Twenty-five patients with type II SMA (mean age of 13.7 +/- 7.0 years) and 15 patients with type III SMA (mean age of 13.7 +/- 8.2 years) were enrolled to undergo a muscle strength evaluation using the method of manual muscle testing. For each patient, the strength of 71 muscle groups were graded using a numerical ordinal scale to obtain individual muscle group scores, average scores of the arms, legs, the musculatures around the limbs' joints, the arm flexors and extensors, and leg flexors and extensors. The data were analyzed using a statistic model of multivariate analysis of variance and paired t-test. All data were administrated respectively for type II and type III SMA. The results showed that in both types of patients, the trunk muscles and the musculatures around the hips possessed lower strength scores, whereas elbow flexors, wrist flexors and extensors, finger flexors, and diaphragms exhibited relatively higher strength scores. In type II SMA the average scores of the musculatures of the left side arms was lower than those of the right side at the joints of scapulas, elbows and wrists. Our data also showed the arm flexor scores were higher than the arm extensor scores in both types, whereas significant higher score of the leg flexor in comparison to the leg extensor was only found in the patients with type II SMA. The profiles of muscle strength and strength differences over various body parts in the patients with type II SMA as well as the type III SMA were obtained from this study.