Sleep architecture in children with spinal muscular atrophy type 2

There have been few published reports on the sleep patterns of patients with spinal muscular atrophy (SMA) type 2, and none on sleep microstructure. The aim of this study was to analyze sleep architecture and microstructure in a group of children with SMA type 2, compared with age-matched and sex-matched controls.

Seventeen SMA type 2 children (seven males, mean age 4.2 years) and 12 controls (five males, mean age 5.0 years) underwent full polysomnography to evaluate sleep architecture and microstructure by means of the Cyclic Alternating Pattern (CAP).

Compared with the control children, the SMA type 2 patients showed a mild increase in the apnea/hypopnea index. Sleep was characterized by a decrease in the number of sleep stage shifts per hour, of percentage of stage N3, of stage R, and of sleep efficiency. On the contrary, significant increases of awakenings per hour, wake after sleep onset, and percentage of stage N1 were found. The CAP analysis revealed a significant increase in the percentage of A1 CAP subtypes, a reduction of that of A3 subtypes, and of A2 and A3 indexes.

The results indicated an abnormality of sleep macrostructure and microstructure in SMA type 2 patients, which was characterized by a reduction of A2 and A3 subtypes (low and high power arousals), supporting the concept of a decreased arousability in SMA type 2 patients. Similar to a previous report on SMA type 1, the findings might be additional proof of central nervous system involvement, although these alterations are less severe than those observed in infants with SMA type 1.