Background: Respiratory muscle weakness is an important feature of spinal muscular atrophy (SMA). Progressive lung function decline is the most important cause of mortality and morbidity in patients. The natural history of lung function in SMA has, however, not been studied in much detail. Results: We analysed 2098 measurements of lung function from 170 treatment-naïve patients with SMA types 1c-4, aged 4-74 years. All patients are participating in an ongoing population-based prevalence cohort study. We measured Forced Expiratory Volume in 1 s (FEV 1), Forced Vital Capacity (FVC), and Vital Capacity (VC). Longitudinal patterns of lung function were analysed using linear mixed-effects and non-linear models. Additionally, we also assessed postural effects on results of FEV 1 and FVC tests. In early-onset SMA types (1c-3a), we observed a progressive decline of lung function at younger ages with relative stabilisation during adulthood. Estimated baseline values were significantly lower in more severely affected patients: %FEV 1 ranged from 42% in SMA type 1c to 100% in type 3b, %FVC 50 to 109%, and %VC 44 to 96%. Average annual decline rates also differed significantly between SMA types, ranging from − 0.1% to − 1.4% for FEV 1 , − 0.2% to − 1.4% for FVC, and + 0.2% to − 1.7% for VC. In contrast to SMA types 1c-3a, we found normal values for all outcomes in later-onset SMA types 3b and 4 throughout life, although with some exceptions and based on limited available data. Finally, we found no important differences in FVC or FEV 1 values measured in either sitting or supine position. Conclusions: Our data illustrate the longitudinal course of lung function in patients with SMA, which is characterised by a progressive decline in childhood and stabilisation in early adulthood. The data do not support an additional benefit of measuring FEV 1 or FVC in both sitting and supine position. These data may serve as a reference to assess longer-term outcomes in clinical trials.

ObjectiveTo investigate probabilities of survival and its surrogate, that is, mechanical ventilation, in patients with spinal muscular atrophy (SMA).MethodsWe studied survival in a population-based cohort on clinical prevalence of genetically confirmed, treatment-naive patients with SMA, stratified for best acquired motor milestone (i.e., none: type 1a/b; head control in supine position or rolling: type 1c; sitting independently: type 2a; standing: type 2b; walking: type 3a/b; adult onset: type 4). We also assessed the need for mechanical ventilation as a surrogate endpoint for survival.ResultsWe included 307 patients with a total follow-up of 7,141 person-years. Median survival was 9 days in SMA type 1a, 7.7 months in type 1b, and 17.0 years in type 1c. Patients with type 2a had endpoint-free survival probabilities of 74.2% and 61.5% at ages 40 and 60 years, respectively. Endpoint-free survival of SMA types 2b, 3, and 4 was relatively normal, at least within the first 60 years of life. Patients with SMA types 1c and 2a required mechanical ventilation more frequently and from younger ages compared to patients with milder SMA types. In our cohort, patients ventilated up to 12 h/d progressed not gradually, but abruptly, to ≥16 h/d.ConclusionsShortened endpoint-free survival is an important characteristic of SMA types 1 and 2a, but not types 2b, 3, and 4. For SMA types 1c and 2a, the age at which initiation of mechanical ventilation is necessary may be a more suitable endpoint than the arbitrarily set 16 h/d.

ObjectivesIn addition to breathing problems, patients with Robin sequence (RS) often encounter feeding difficulties (FD). Data regarding the occurrence of FD and possible influencing factors are scarce. The study aim was to elucidate these factors to improve treatment strategies.Material and methodsA retrospective comparative cohort study was conducted, consisting of 69 infants diagnosed with both RS and a cleft palate and 64 isolated cleft palate only (iCPO) infants. Data regarding FD, growth, and airway intervention were collected during the first 2 years of life. A systematic review of the literature was conducted to identify reported FD in RS patients.ResultsRS patients had more FD (91 %) than iCPO patients (72 %; p = 0.004). Also, nasogastric (NG)-tube feeding was necessary more frequently and for a longer period (both p < 0.001). Growth was lower in RS than iCPO infants (p = 0.008) and was not affected by the kind of airway management (conservative/surgical; p = 0.178), cleft palate grade (p = 0.308), or associated disorders (p = 0.785). By contrast, surgical intervention subtype did significantly affect growth. Mean reported FD for RS in the literature is 80 % (range = 47–100 %), and 55 % (range = 11–100 %) of infants need NG-tube feeding.ConclusionsFD is present in a large proportion of infants with RS, which indicates the need for early recognition and proper treatment to ensure optimal growth. Growth during the first 2 years of life is significantly lower in RS patients than iCPO patients, which indicates the need for careful attention and long-term follow-up.Clinical relevanceThis study indicates the need for early recognition and proper treatment of FD in RS to ensure optimal growth. In addition, growth needs careful attention and long-term follow-up.