Respiratory Muscle Weakness in Facioscapulohumeral Muscular Dystrophy.

The purpose of this study was to comprehensively evaluate respiratory muscle function in adults with facioscapulohumeral muscular dystrophy (FSHD).14 patients with FSHD (9 men, 53±16 years) and 14 matched controls underwent spirometry, diaphragm ultrasound, and measurement of twitch gastric and transdiaphragmatic pressures (twPgas and twPdi; n=10) following magnetic stimulation of the lower thoracic nerve roots and the phrenic nerves. The latter was combined with recording of diaphragm compound muscle action potentials (CMAP; n=14).

The following parameters were significantly lower in patients vs. controls: forced vital capacity (FVC), maximum inspiratory and expiratory pressure, peak cough flow, diaphragm excursion amplitude and thickening ratio on ultrasound, twPdi (11±5 vs. 20±6 cmH₂ O), and twPgas (7±3 vs. 25±20 cmH₂ O). Diaphragm CMAP showed no group differences. FVC correlated inversely with the clinical severity scale score (r=-0.63, p=0.02).

In FSHD, respiratory muscle weakness involves both the diaphragm and the expiratory abdominal muscles. This article is protected by copyright. All rights reserved.