Table 1 Clinical classification of spinal muscular atrophy
From: Natural history of lung function in spinal muscular atrophy
SMA type and sub-classification | Age at onset | Highest achieved motor milestones |
|---|---|---|
1 | 0–6 months | Never acquires ability to sit unsupported |
0/1a | Prenatal / neonatal | 0/1a: Symptoms in prenatal and/or neonatal period, no head control |
1b (‘classic’) | 1–6 months | 1b: No head control and no ability to roll over |
1c | 3–6 months | 1c: Will usually acquire additional motor skills, such as head control or rolling from supine to prone, or at least to one side at any stage in life. |
2 | 6–18 months | Able to sit unsupported, not able to walk |
2a | 2a: unsupported sitting but not able to stand or walk even with assistance | |
2b | 2b: in addition to unsupported sitting also able only with assistance to stand or even walk a few steps | |
3 | > 18 months | Able to walk unsupported |
3a | 18–36 months | |
3b | > 36 months | |
4 | During adulthood, i.e. ≥ 18 years | Able to walk unsupported |