The influence of handedness on the distribution of muscular weakness of the arm in facioscapulohumeral muscular dystrophy

Abstract

The strength of 10 muscle groups in both arms was measured using hand-held myometry to determine the influence of handedness on left-right differences of muscle strength in facioscapulohumeral muscular dystrophy (FSHD). Two groups of subjects were studied: 24 healthy volunteers (19 right-handed), and 53 patients (42 right-handed) with autosomal dominant FSHD. An opposite left-right difference of strength of shoulder and arm muscles was found: right-handed volunteers were stronger on the right side, right-handed patients were stronger on the left side. This opposite left-right difference was statistically significant for the supraspinatus muscle, the wrist extensors and the shoulder internal rotators. The number of left-handed subjects was too small for statistical analysis. The relation between handedness and increased muscle weakness in right-handed FSHD patients suggests that mechanical factors may play a distinct role in the progression of muscle weakness in FSHD.