Respiratory status in children with spinomuscular atrophy type II & III

Abstract

Introduction: Spinomuscular atrophy (SMA) is an uncommon, progressive Neuromuscular Disorder (NMD) with significant respiratory morbidity and eventual respiratory failure. There are currently no clear guidelines for non-invasive ventilation (NIV) instigation in this condition. Newer treatment options are likely to change current clinical practices but improved respiratory assessment methods are needed. Our objectives in this cohort were to (1) analyse the patterns of sleep breathing measured by polysomnography (PSG) and (2) determine early clinical and lung function predictors of nocturnal hypoventilation. Methods: We retrospectively reviewed clinical records and PSG data of all children with genetically-confirmed SMA II/III living in Queensland. Spirometry, Forced Oscillatory Technique (FOT), Lung Clearance Index (LCI), & respiratory muscle strength testing were prospectively performed/ measured. The prospective arm of the study is ongoing with complete data collection expected by November 2017. Results: 23 children (9F; 17 with SMA II, median age 108 months) were included. Median FVC% predicted (z score) was 61% (n=19, -3.32); Rrs8 z-score: 2.19 (n=11); Xrs8 z-score: -2.03 (n=11); SNIP z-score: -2.53 (n=10) & LCI: 7.36 (n=12). Median (IQR) REM related Apnea-hypopnea index (rAHI) was high at 5.9 (2.9-17.5;n=19). 10 children (9 with SMA II) required long-term nocturnal NIV initiated at a median age of 94 months; 5 (50%) after an acute respiratory illness. These children were older (127 vs 84 months; p=0.03) with significantly worse FVC-z scores (-4.8 vs -1.18; p<0.01); rAHI (26.5 vs. 4.2; p=0.05), LCI (8.8 vs. 7.1, p=0.01) & SNIP z-scores (-3.5 vs. -1.47 p=0.001). Predictors of NIV need will be analysed using a logistic regression model once the prospective arm is completed. Conclusion: Most children with SMA II need nocturnal ventilatory support beginning in early childhood and FVC may be a predictor. FOT, SNIP and LCI were deranged and may help in predicting early respiratory insufficiency, particularly in early years.L6220917182018-05-16 <br />