Respiratory function in 192 adult patients with spinal muscular atrophy (SMA) treated with nusinersen - a multicenter observational study.

BACKGROUND

Natural history data show that respiratory function is impaired in SMA patients. Observational studies have shown stabilization of respiratory function in adult SMA patients treated with nusinersen. However, long-term studies investigating the effect of nusinersen on respiratory function in adult SMA patients are rare.

METHODS

We examined respiratory function using forced vital capacity of predicted normal (FVC%), FVC in liters, capacity per second (FEV1) and peak expiratory flow (PEF) in 192 adult SMA patients treated with nusinersen for a median of 3.2 years (IQR: 2.1–4.0, range: 0.2–5.2). Changes in spirometric parameters were analyzed using individual linear regression models separate in each patient to estimate the slope. Additionally, three multivariable models were performed to assess the effect of age, sex, treatment duration, baseline FVC% and each one of the variables of interest (1) SMA type, (2) ambulation status, (3) spondylodesis on follow-up FVC%. Associations between respiratory parameters and motor function (HFMSE) were investigated via Scatter plots and Spearman’s rank correlation.

RESULTS

Spirometric parameters remained stable during treatment (median annual rate of change of FVC% 0.17% (p = 0.40), FVC in liters  -0.002 (p = 0.59), FEV1 -0.014 l (p = 0.06) and PEF 0.025 l/s (p = 0.65)). In all multivariable models, age, sex, treatment duration, SMA type, ambulation status, and spondylodesis showed no significant association with follow-up FVC%. No significant correlations were observed between respiratory and motor function.

CONCLUSION

Respiratory parameters remained stable during treatment with nusinersen in adult SMA patients over several years. CLINICAL TRIAL NUMBER: Not applicable.