Creatine kinase levels are typically normal in SMA type 1 and normal or slightly elevated in the other types.
Electrophysiologic studies are useful in differentiating SMAs from other neurogenic and myopathic diseases. In most cases, sensory nerve conduction is normal in SMA, with the exception of Kennedy and Davidenkow syndromes.
Homozygous SMN1 gene deletion is both sensitive (95%) and specific (nearly 100%) for the diagnosis of SMA. Molecular testing for homozygous deletion or mutation of the SMN1 gene allows efficient and specific diagnosis.
The cardiac system is usually unaffected in SMA, and ECGs are normal.
Learn more about the workup for SMA.
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Cite this: Stephen L. Nelson. Fast Five Quiz: Spinal Muscular Atrophy - Medscape - Jan 14, 2021.