“The age at which Spinal Muscular Atrophy-SMA symptoms begin roughly correlates with the degree to which motor function is affected: The earlier the age of onset, the greater the impact on motor function.  SMA involves the loss of nerve cells called motor neurons in the spinal cord and is classified as a motor neuron disease.In the most common form of SMA (chromosome 5 SMA, or SMN-related SMA), there is wide variability in age of onset, symptoms, and rate of progression. On Dec. 23, 2016, the U.S. Food and Drug Administration (FDA) approved Spinraza (nusinersen) for the treatment of SMA. Spinraza is designed to treat the underlying defect in SMA, which means it potentially may be effective at slowing, stopping, or perhaps reversing the symptoms of SMA.”

MDA Muscular Dystrophy Association