Posterior spinal fusion in patients with spinal muscular atrophy: a surgical technique to allow intrathecally inject nusinersen

Background: Nusinersen, the recently approved medical therapy in the treatment of spinal muscular atrophy (SMA), has revolutionized the natural history of this disease. Until now, surgical treatment of scoliosis in SMA patients was an exclusion criterion for drug therapy. In fact, the bone graft positioned posteriorly during surgery, in order to obtain a solid fusion, prevented the lumbar puncture necessary for the intrathecal administration of the drug. The aim is to describe a surgical technique that allows for safe and easy intrathecal administration of nusinersen. Methods: We present a single-center, single-surgeon case series descriptive study. From 2019 to 2021 seven consecutive patients affected by genetically confirmed SMA suitable for treatment with nusinersen and suffered from neuromuscular scoliosis needing posterior spinal fusion surgery were included in the present study. During posterior spinal fusion surgery a L3-L4 or L2-L3 laminectomy was performed to provide safer access to intrathecal injection. The drainage scar was used as a skin landmark so as to facilitate future procedures. Results: The median of operative time was 250 min (range: 200-370 min). The median correction rate was 57% (range: 43.5-68). The median of intraoperative blood loss was 650 mL (range 320-940 mL). The median value of the correction loss at the last follow-up was 10% (range: 4.5-15%). Conclusions: The surgical procedure allowed all patients to receive nusinersen therapy without complications. The procedure described is simple and effective in providing safe intrathecal access to make these patients suitable for undertaking or continuing the protocol of treatment with nusinersen.