SUZANNE GRALA / SCIENCE PHOTO LIBRARY SUZANNE GRALA / SCIENCE PHOTO LIBRARY
Woman with spinal muscular atrophy in wheelchair. Spinal muscular atrophy (SMA) is a genetic disease which causes the degeneration of motor neurones in the anterior horn of the spinal cord. Motor neurones are nerve cells in the spinal cord that send impulses to the muscles, telling them to expand or contract. The deterioration of the motor neurons gradually breaks the link between the brain and the muscles that this part of the spinal cord controls. As degeneration progresses, the muscles controlled by the spinal cord are used less and less, so they become weaker and shrink (atrophy). There is no known cure for SMA.
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