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Updated: Dec 19, 2025
Electrophysiological Motor Unit Number Estimation MUNE Measuring Compound Muscle Action Potential CMAP in Mouse Hindlimb Muscles
Published on: September 25, 2015
Whole blood survival motor neuron protein levels correlate with severity of denervation in spinal muscular atrophy
Christiano R R Alves1, Ren Zhang1, Alec J Johnstone1
1Department of Neurology, Center for Genomic Medicine, Massachusetts General Hospital, Boston, Massachusetts.
Introduction:
We sought to determine whether survival motor neuron (SMN) protein blood levels correlate with denervation and SMN2 copies in spinal muscular atrophy (SMA).
Methods:
Using a mixed-effect model, we tested associations between SMN levels, compound muscle action potential (CMAP), and SMN2 copies in a cohort of 74 patients with SMA. We analyzed a subset of 19 of these patients plus four additional patients who had been treated with received gene therapy to examine SMN trajectories early in life.
Results:
Patients with SMA who had lower CMAP values had lower circulating SMN levels (P = .04). Survival motor neuron protein levels were different between patients with two and three SMN2 copies (P < .0001) and between symptomatic and presymptomatic patients (P < .0001), with the highest levels after birth and progressive decline over the first 3 years. Neither nusinersen nor gene therapy clearly altered SMN levels.
Discussion:
These data provide evidence that whole blood SMN levels correlate with SMN2 copy number and severity of denervation.
