The utility of compound muscle action potential and creatinine in childhood spinal muscle atrophy

Background Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder precipitated by mutations in the survival motor neuron 1 gene (SMN1). Given the significant heterogeneity in patients' responses to Nusinersen treatment, there is an urgent need for sensitive biomarkers in SMA to accurately evaluate the beneficial effects of these therapeutic interventions. We explored the association between motor scores and serum creatinine (Crn) levels and compound muscle action potential(CMAP) in SMA patients undergoing treatment with nusinersen. Methods We measured serum Crn levels, CMAP amplitude and Hammersmith Functional Motor Scale-Expanded (HFMSE), including 40 pediatrics patients with SMA. The association between Crn ,CMAP and motor scores was investigated through partial rank correlation analysis and linear mixed models. Results 40 pediatrics patients were included. Among them, 35 patients had Nusinersen treatment. Nine patients did not have their CMAP amplitude and motor scores data recorded during the follow-up therapy period. Four patients only had their motor scores available during the follow-up therapy, while 22 patients had both their CMAP amplitude and motor scores measured during the follow-up therapy. Except for femoral nerve, the amplitudes of the left tibial, peroneal, ulnar, and median nerves demonstrated enhancements following nusinersen treatment(P<0.05), as well as HFMSE. Both at the baseline assessment and during the follow-up period, the left tibial, peroneal, ulnar, and femoral nerves showed correlations with the HFMSE(p<0.05). After accounting for the effects of age and sex, Crn were found to be associated with motor scores and the ulnar CMAP amplitude at baseline and follow-up(p<0.05). The CMAP amplitude of the ulnar nerve at baseline exhibited predictive value in indicating motor function improvement in SMA patients(p=0.012). Conclusions In conclusion, for patients with SMA who were treated with nusinersen, notable improvements in motor scores and CMAP were observed. Crn at baseline and follow-up had relationship with HFMSE. The CMAP amplitude of the ulnar nerve at baseline exhibited predictive value in indicating motor function improvement in SMA patients.