Diaphragm ultrasonography in amyotrophic lateral sclerosis: a diagnostic tool to assess ventilatory dysfunction and disease severity

BACKGROUND: Respiratory failure represents an unavoidable step in patients with amyotrophic lateral sclerosis (ALS) and other motor neuron diseases (MND). The development of diaphragm ultrasonography (DUS) provides an alternative useful and risk-free tool to supply clinical, functional, and neurophysiological assessment of respiratory muscle weakness. Our aim was to evaluate if sonographic changes (thickness and echogenicity in the costal portion of the diaphragm, at rest and during respiratory movements) may be used in ALS patients to assess disease severity over time, to rule out any risk or discomfort due to traditional neurophysiological investigations. METHODS: Twenty ALS patients (mean age, 64.6 ± 10.5 years) were enrolled and data were compared with age-matched healthy volunteers; DUS data were correlated with respiratory function and disease severity scale. Examinations were performed using Telemed Echo-wave II or Esaote MyLabGamma devices in conventional B-Mode. RESULTS: Mean resting thickness was reduced in all cases; changes in thickness during inspiration and expiration were also reduced (p < 0.0001) and lost in severe cases (n = 3). In bulbar-onset disease, respiratory scores were strictly correlated with the difference in diaphragm thickness between full inspiration-and expiration-as well as on the diaphragm thickness in expiration (p < 0.001). CONCLUSIONS: DUS represents a simple, painless, and risk-free tool; moreover, it provides useful functional and structural insights to the understanding of diaphragm function and the degree of respiratory failure in ALS.