O2070: A Changing EOS Phenotype in SMA: Nusinersen Use is Associated with Increased Curve Magnitude and Kyphosis at the Time of Index Surgery

Background: Nusinersen provides functional benefits to spinal muscular atrophy (SMA) patients but does not affect the prevalence or progression of scoliosis. The effect of nusinersen on curve characteristics in SMA has not been described. Here, we investigate curve characteristics associated with nusinersen use in an SMA patient population undergoing initial surgical treatment for early onset scoliosis (EOS). We hypothesize that Nusinersen administration affects preoperative curve characteristics and flexibility among patients with SMA and EOS .

Methods: A multicenter international pediatric spinal deformity database was queried for SMA patients undergoing initial surgical treatment (index growing construct implantation or definitive fusion) for scoliosis. Patients were stratified by exposure to nusinersen preoperatively. Preoperative clinical and radiographic characteristics and first erect postoperative radiographic parameters were compared between the two groups.

Results: 225 patients were identified, 187 of which were controls (nusinersen naïve) and 38 who were treated with nusinersen preoperatively. Patients in the nusinersen group were treated for a median of 1.9 years(range: 0.02 - 5.9) before surgery. The mean age at surgery in the nusinersen group was lower than controls, 6.4 vs 7.7 years (p=0.002). The nusinersen group was more likely to be treated with MCGR 87% vs 45% (p < 0.001). 80% of patients were instrumented to the pelvis, which did not differ between the two groups. Mean preoperative major curve and kyphosis were higher among the nusinersen group vs controls 83°vs 74° (p=0.023) and 77° vs 66° (p=0.021) respectively. The mean percent coronal correction was 46%, and the mean change in kyphosis was 25° and did not differ between the groups. Mean preoperative pelvic obliquity was 20°, was corrected an average of 47%, and did not differ between the groups.

Conclusion: Nusinersen use was associated with larger, more kyphotic curves and younger age at intervention among SMA patients undergoing initial surgical treatment for EOS. The percent correction of the curves was similar, suggesting similar curve flexibility. Further study is needed to understand if Nusinersen directly affects curve characteristics or rather improves function in more severely affected patients, allowing them to become surgical candidates.