Intrathecal catheter and port placement for nusinersen infusion in children with spinal muscular atrophy and spinal fusion

Unilateral interlaminar fenestration on the convex side provides a reliable access for intrathecal administration of nusinersen in spinal muscular atrophy: a retrospective study

BACKGROUND

As the first gene therapy for spinal muscular atrophy (SMA), nusinersen is supposed to be administrated via intrathecal injection regularly for a lifetime. However, for SMA patients with severe spinal deformities, bony fusion following posterior spinal instrumentation sets great obstacles for the application of nusinersen. Therefore, efforts have been devoted to the exploration of appropriate approach for nusinersen administration. This study aims to evaluate the safety and reliability of unilateral interlaminar fenestration on the convex side during spinal fusion surgery for intrathecal nusinersen injection in SMA.

RESULTS

SMA patients receiving posterior spinal fusion and interlaminar fenestration in Peking Union Medical College Hospital from January 2020 to October 2021 were retrospectively analyzed. 13 patients were included. Of the 13 patients, 10 were classified into SMA type II and 3 into SMA type III. Distal fusion to pelvis was undertaken in 11 patients; while L5 was selected as the lowest instrumented vertebra in the other 2 patients. All patients received interlaminar fenestration on the convex side only with an area of about 15 mm × 20 mm. Fenestration at L2-L3 level was performed in 6 patients; while L3-L4 level was selected for windowing in the remaining 7 patients. 9 of the 13 patients received lumbar puncture and intrathecal nusinersen administration during the 1-year follow-up, with an accumulative total of 50 times. All injections were performed successfully under ultrasound guidance, with no one transferred to radiographic assistance. No severe complications occurred after injection.

CONCLUSIONS

In SMA with severe scoliosis planning to receive posterior spinal fusion, unilateral lumbar interlaminar fenestration on the convex side provides a feasible and reliable access for intrathecal nusinersen administration after surgery.

Nusinersen for Patients With Spinal Muscular Atrophy: 1415 Doses via an Interdisciplinary Institutional Approach

BACKGROUND

Spinal deformity and prior spinal fusion pose technical challenges to lumbar puncture (LP) for nusinersen administration for patients with spinal muscular atrophy (SMA). In this retrospective study over two study phases, we evaluated (1) factors associated with difficult LP or unscheduled requirement for image guidance and (2) effectiveness of a triage pathway for selective use of image guidance and nonstandard techniques, particularly for patients with spinal instrumentation/fusion to the sacrum.

METHODS

With institutional review board approval, electronic health records, imaging, and administrative databases were analyzed for patients receiving nusinersen from January 2012 through September 2021. Descriptive statistics and univariate analyses were used.

RESULTS

From January 2012 to March 2018 (phase 1), among 82 patients with SMA, 461 of 464 (99.4%) LP attempts were successful. Univariate analyses associated difficulty with prior spinal instrumentation, higher body mass index, and severity of the spinal deformity. Based on this experience, starting in April 2018 (phase 2), 125 patients were triaged selectively for ultrasound, fluoroscopy, or Dyna computed tomography. Patients with spinal instrumentation/fusion to the sacrum were treated primarily via intrathecal ports (137 doses) or transforaminal LP (55 doses). From April 2018 through September 2021, 704 of 709 (99.3%) LPs were successful. In total from January 2012 to September 2021, 1415 doses were administered. Over 50% of LPs were performed by neurology nurse practitioners without image guidance. Safety outcomes were excellent.

CONCLUSIONS

A stratified approach resulted in successful intrathecal nusinersen delivery and efficient resource allocation for patients with SMA, with or without complex spinal anatomy.

Transforaminal lumbar puncture for spinal anesthesia or novel drug administration: a technique combining C-arm fluoroscopy and ultrasound

Background

Lumbar puncture (LP) may be challenging for patients with scoliosis and other conditions following previous posterior fusion and instrumentation from thoracic to sacral levels. Interventional radiologists have described CT approaches to transforaminal LP. We hypothesized that combined C-arm fluoroscopy and ultrasound could be a feasible approach to transforaminal LP for interventional pain physicians and regional anesthesiologists.

Methods

With institutional review board approval, we reviewed medical records and imaging of six patients with spinal muscular atrophy and prior spine fusion. Non-cutting needles of 24 or 25 gage were advanced through 20-gage introducers. Prior imaging guided selection of a preferred side and spinal level. Initial procedures were performed in the interventional radiology suite. Subsequent procedures were performed in an operating room (OR). We report on technical success and complications and describe a case using this approach for spinal anesthesia.

Results

Six patients underwent a total of 54 transforaminal LPs, including 51 for administration of the antisense oligonucleotide nusinersen, 2 for myelography, and 1 for spinal anesthesia; 45 of these procedures were performed using OR C-arm fluoroscopy and ultrasound. Transient paresthesias and short-term headaches occurred; none required intervention. No other complications were noted.

Conclusions

Transforaminal LP appears technically feasible for patients with full-spine fusions using a straight-needle approach with combined fluoroscopy and ultrasound guidance. Larger case series and prospective studies may better define the success rates, risks, and benefits of this approach relative to alternative approaches to intrathecal access for patients with previous long-segment posterior spine fusions.

Disease Modifying Therapies for the Management of Children with Spinal Muscular Atrophy (5q SMA): An Update on the Emerging Evidence

SMA (5q SMA) is an autosomal recessive neuromuscular disease with an estimated incidence of approximately 1 in 11,000 live births, characterized by progressive degeneration and loss of α-motor neurons in the spinal cord and brain stem, resulting in progressive muscle weakness. The disease spectrum is wide, from a serious congenital to a mild adult-onset disease. SMA is caused by biallelic mutations in the SMN1 gene and disease severity is modified primarily by SMN2 copy number. Before the advent of specific disease altering treatments, SMA was the second most common fatal autosomal recessive disorder after cystic fibrosis and the most common genetic cause of infant mortality. Nusinersen, risdiplam, and onasemnogene abeparvovec are presently the only approved disease modifying therapies for SMA, and the aim of this review is to discuss their mode of action, effects, safety concerns, and results from real-world experience. All exert their action by increasing the level of SMN protein in lower motor neuron. Nusinersen and risdiplam by modifying the SMN2 gene product, and onasemnogene abeparvovec by delivering SMN1 gene copies into cells. All have an established clinical efficacy. An important feature shared by all three is that early intervention is associated with a better treatment outcome, such that in cases where treatment is initiated in an early pre-symptomatic period, it may result in normal – or almost normal – motor development. Thus, early diagnosis followed by swift initiation of treatment is fundamental for the treatment response and consequently long-term prognosis in SMA type 1, and probably SMA type 2. The same principle similarly applies to the milder phenotypes. All three therapies are relatively novel, with risdiplam being the latest addition. Except for nusinersen, real-world data are still scarce, and long-term data are quite naturally lacking.