Current Series: Advances in the Treatment of Spinal Muscular Atrophy

Crystal Proud, MD: Hello and welcome to this NeurologyLive® Peer Exchange titled, “Advances in the Treatment of Spinal Muscular Atrophy.” I am Dr Crystal Proud, from the Children’s Hospital of the King’s Daughters. Joining me today in this virtual discussion are my colleagues, Dr John Brandsema, from the Children’s Hospital of Philadelphia; Dr Nancy Kuntz, from the Ann and Robert H. Lurie Children’s Hospital of Chicago; and Dr Julie Parsons, from the Children’s Hospital of Colorado. 
Today, we are going to discuss a number of topics pertaining to the diagnosis and treatment of spinal muscular atrophy [SMA]. Let’s get started on our first topic. Spinal muscular atrophy is the result of a missing or mutated SMN1 gene. Its estimated prevalence is about 1 in 10,000. John, could you please review for us the signs and symptoms of spinal muscular atrophy that might lead a pediatrician to suspect this diagnosis? 
John Brandsema, MD: I think it's important to distinguish that spinal muscular atrophy is a broader term that includes a lot of heterogeneous clinical syndromes, but when we're speaking about the most common form, 5q SMA, this tends to be a degeneration of motor neurons in the spinal cord and brain stem. What you see as symptoms universally in the disorder are weakness in the limbs, and in children that often manifests as motor delays and hypotonia. 
As you get into the more severe forms of the disease, you start to see the brainstem involvement, and that would include bulbar symptoms, such as difficulty swallowing and speaking, and respiratory involvement. The respiratory involvement is a bit unique in this disorder because the paraspinal musculature is more affected than the diaphragm, which is relatively spared. Because of this, the children often develop a paradoxical breathing pattern, where they tend to breathe contrary to what they're trying to do inspiration- versus expiration-wise.  
This also leads to a remodeling of the chest shape, in the most severe form looking more bell-shaped in the torso. Pediatricians will probably be seeing patients for initial delays in motor development and weakness and hypotonia, which eventually leads to regression in all forms of the disease, which is progressive and the natural history. 
Crystal Proud, MD: Thank you for summarizing that for us.