Clinical factors as predictors of survival in spinal muscular atrophy type I

The aim of this study was to establish whether clinical factors may help to identify subgroups of infants with spinal muscular atrophy (SMA) type I. A questionnaire was retrospectively proposed to 38 families of infants with SMA type I. It included questions regarding possible prenatal and early neonatal signs of motor and/or respiratory weakness, onset and progression of clinical signs, and age at death for those infants who had not survived beyond the age of 30 months. As we also wished to establish whether the severity of onset of clinical signs and their progression are predictors of outcome, and in order to have a homogeneous group, we only included families where the affected child had not received any respiratory support or noninvasive ventilation. In the population of SMA type I patients, statistical analysis of the questionnaire allowed to identify three subgroups of the disease: (1) neonatal SMA; (2) classical SMA type I; (3) SMA intermediate between type I and type II. This would be useful for correct stratification of patient groups and should be considered when establishing inclusion criteria for future trials in SMA type I patients.