Fig. 1.

SMA Pathophysiology and Candidate Biomarkers. A number of candidate biomarkers have been proposed based on the pathophysiology of SMA. Genetic factors impacting the expression of SMN protein include SMN2 copy number and polymorphisms, the presence of modifier genes that can improve downstream neuronal and motor functions associated with SMA disease state, and gene transcription factors that affect the expression of SMN2 and other genes. Muscle presence and function can be measured through a variety of techniques including imaging, action potential and electrical response following motor nerve stimulation, and quantification of molecular factors that relate to muscle metabolism or damage. The presence of neurofilament in serum and CSF has been the subject of extensive research.