The following is a general guide to SMA classification. Some cases of SMA may not fall clearly into only one category.
Weakened muscles affect crying, sucking, breathing and swallowing.
Onset is usually before six months of age. The child's intellect is not affected. The muscle weakness experienced by these babies is severe, with some infants being almost completely immobile. Survival beyond the third year of life, while occasionally seen, is rare. Depends on the degree of respiratory involvement Also known as SMA Type II, intermediate SMA is apparent within the first year to eighteen months of life with weakness and loss of functional ability.