“Regarding SMA:

• Spinal muscular atrophy (SMA) is a disorder affecting the motor neurons—nerve cells that control voluntary muscle movement. These cells are located in the spinal cord.
• Because the muscles cannot respond to signals from the nerves, they atrophy — weaken and shrink — from inactivity.
• One in every 6,000 babies is born with SMA. It is one of the most prevalent genetic disorders affecting young children and a major cause of death in infancy.
• SMA can strike children at any age. SMA in infancy and early childhood is associated with worse outcomes, while patients who develop symptoms later in childhood or in adolescence usually have a more positive prognosis.
• SMA does not affect sensory nerves or intellect, but it has been observed that many patients with SMA are highly intelligent.”

John Hopkins Medicine (Spinal Muscular Atrophy (SMA) | Johns Hopkins Medicine)