Purpose or Case Report: To describe alternative routes of Nusinersen administration in patients in whom traditional lumbar puncture is limited secondary to spinal hardware and bony fusion.
Methods & Materials: At our institution, we now have approximately 35 spinal muscular atrophy (SMA) patients receiving Nusinersen. Many type 2 and 3 SMA patients have severe scoliosis necessitating spinal fusion and rod placement. The associated new bone formation and bone grafts often preclude traditional lumbar puncture. In these patients, we order pre-procedure CT of the lumbar spine and MR of the cervical spine. Images are evaluated for possible trans-foraminal or cervical (C1-C2 or occiput-C1) puncture. Some institutions have reported the surgical creation of an access point for injection by drilling through the posterior bony mass. This places the patient at risk of surgery and the burr hole has a tendency to close up in time.
Results: In all patients with spinal fusion and hardware, a location for safe needle access was identified. Given our lack of comfort with transforaminal access initially, we began performing these with cone beam guidance. In time, we became comfortable with fluoroscopy alone. Additionally, we initially successfully performed three injections via cervical puncture. However, with the success of the transforaminal approach, these patients have now been converted to fluoroscopic transforaminal technique. In several patients, a small window in the otherwise fused posterior elements was identified by pre-procedure CT. Using 3D reconstructions, these windows were identified fluoroscopically and accessed via midline or interlaminar approach.
Conclusions: The presence of extensive bony fusion and spinal hardware should not preclude a patient from therapy or necessitate the surgical creation of an route for Nusinersen injection, given the available non-surgical alternative routes of administration. Cone beam CT is not generally needed, but may be reserved for difficult cases.