Clinical characteristics of participants in each SMA phenotypic subgroup and for the total cohort
| Characteristics | SMA type 1, N=6 | SMA type 2, N=10 | SMA type 3, N=4 | Total, N=20 |
| Sex | ||||
| Male | 2 (33%) | 6 (60%) | 3 (75%) | 11 (55%) |
| Female | 4 (66%) | 4 (40%) | 1 (25%) | 9 (45%) |
| SMN2 copy number | ||||
| 2 | 1 (17%) | 1 (11%) | 1 (25%) | 3 (16%) |
| 3 | 5 (83%) | 8 (89%) | 3 (75%) | 16 (84%) |
| Age at symptom onset (months) Median, (range), SD | 3.5, (2–5), 1.11 | 12, (8–18), 7.8 | 22.5, (18.5–144), 65.2 | 12, (2–144), 30.5 |
| Age at time of study (months) Median, (range), SD | 11.5, (4–178), 67.7 | 99, (13–153), 42 | 127.5, (109–193), 37.2 | 99, (4–193), 59.3 |
| Disease duration (months) Median, (range), SD | 7.2 (2–175), 68.2 | 77 (1–141), 41.7 | 104.5 (52–114), 29 | 63 (2–175), 51.6 |
| Duration of study follow-up (months) Median, (range), SD | 26.8, (21.5–33.5), 5.0 | 12.8, (4 -26), 5.9 | 12, (6–14), 3.8 | 13.8 (4–33.5), 8.6 |
Classification of SMA phenotype for this study adhered to guidelines set out in the International Collaborative SMA Workshop16; SMA type 1 (symptom onset <6 months, unable to sit independently), SMA type 2 (symptom onset 7–18 months, sits independently) and SMA type 3 (symptom onset >18 months of age, walks independently at time of diagnosis).
Age at the time of study, age at symptom onset, disease duration (interval between age of symptom onset and age at first nusinersen treatment) and study follow-up duration are expressed as median, (range), standard deviation (months).
Sex and SMN2 copy number of participants in each SMA phenotypic subgroup and for the total cohort are expressed as n (%).
*Nineteen out of 20 (95%) of children had SMN2 copy number available (missing data for a child with SMA type 2 phenotype).
SMA, spinal muscular atrophy.