Recent research in adults has shown that skeletal muscles express cardiac isoforms of troponin T (cTnT) in several neuromuscular diseases without cardiomyopathy. We examined whether increased serum cTnT is detectable also in SMA patients and if it correlates with disease severity. The new therapy with Nusinersen has shown to improve motor function. We evaluated whether this treatment has an effect on muscle mass, measured by serum creatinine and whether it changes cTnT. Between 03/2016 and 03/2018 we collected data of 16 patients with SMA (SMA1: 6, SMA 2 or 3: 10). Serum samples were obtained as part of the routine work-up before treatment initiation and prior to each applied dose. The high sensitivity cTnT test (hs cTnT, Roche Cobas) was used. Cardiac disease was excluded clinically, by echocardiography and by measuring cTnI. Serum creatinine (SC) was chosen as surrogate for muscle mass. Disease severity was determined by SMA type and in patients with SMA1 by the need for ventilation within two months after initiating treatment. While all cTnI levels were within the normal range, baseline cTnT in SMA1 patients was 80±39 (range 43-143ng/L) and thus 3 to 10-fold above the upper limit of normal of 14 ng/L. Values of non-ventilated patients were lower than in ventilated patients (p=0,06). SMA2/3 had significantly lower cTnT and cTnT/SC than SMA1 patients (p=0,0002 and p=0,06). After the third application of Nusinersen no significant changes in SC, cTnT, or cTnT/SC could be detected in all SMA groups. As our pilot study shows that cTnT is elevated in all patients with SMA1, it might be useful as a screening tool. As expected, cTnT was correlated with disease severity. We found no support for our hypothesis that Nusinersen improves muscle mass and decreases cTnT. However, small sample size, short follow-up period, and the lack of a control group make a reliable statement impossible. Further studies with larger patient groups including untreated controls are essential.