Spinal Muscular Atrophy: Scoliosis

Spinal Muscular Atrophy: Scoliosis

Scoliosis is an early orthopedic complication of Spinal Muscular Atrophy (SMA).1 The estimated incidence of scoliosis in SMA types 1 and 2 ranges from 60-90%2 and is approximately 50% in SMA type 3.3 The etiology of scoliosis in SMA is weakness throughout the muscles in the thoracic compartment leading to a progressive spinal column deformity with pelvic obliquity.1,2,4 Patients with SMA have poor respiratory effort due to weakness creating less respiratory resistance to scoliotic changes and an accelerated rate of deformity.4 Scoliosis reduces respiratory capacity in patients with SMA and worsens their respiratory impairment.5 Scoliosis can exacerbate sitting difficulties.6 Intrathecal treatments for SMA are more complicated in patients with spinal anatomy affected by scoliosis.7

A consortium of SMA experts recommends that practitioners inspect the spine as part of routine clinical evaluation of patients with SMA. In patients with suspected or visible scoliosis, the consensus among SMA experts is to perform radiography to define the extent of scoliosis. In patients with >20 degrees of scoliosis, these experts advise follow-up imaging every 6 months until patients achieve skeletal maturity and annually thereafter.2

The consensus among experts in SMA is that conservative measures like physical therapy and bracing to treat scoliosis can be used for Cobb angles exceeding 15-20 degrees and less than 50 degrees.2 There is not consensus regarding whether soft or rigid thoracolumbar corset braces work best in SMA.2 The decision of what brace a patient uses should be made individually based on patients’ varying support needs with awareness that in some instances bracing can degrade respiratory capacity.5

Braces can slow scoliosis progress but will not arrest progress entirely.1 Experts in SMA recommend considering surgical intervention for Cobb angle exceeding 50 degrees.2 Surveys of patients with SMA find that the majority of patients with SMA undergo scoliosis surgery.3,8 With the approval of the first effective therapy for SMA, there is an expectation that surgical repair will become even more common.2 Experts recommend waiting until after four years of age to attempt repair and the use of “growth-friendly” hardware in patients less than ten years old. 

Outcomes of scoliosis repair in SMA appear to favor benefit over risk, but there can be serious post-operative complications.3,9 Lung function in patients with SMA is improved and sustained after scoliosis repair.10,11 There is a report of gastroesophageal reflux improvement after scoliosis repair in a patient with SMA.12 Patients with SMA report reduced pain, better function, and higher quality of life after scoliosis surgery.13

References

1. Mayer OH. Scoliosis and the impact in neuromuscular disease. Paediatr Respir Rev. Jan 2015;16(1):35-42.

2. Mercuri E, Finkel RS, Muntoni F, et al. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscul Disord. Feb 2018;28(2):103-115.

3. Catteruccia M, Vuillerot C, Vaugier I, et al. Orthopedic Management of Scoliosis by Garches Brace and Spinal Fusion in SMA Type 2 Children. J Neuromuscul Dis. Nov 21 2015;2(4):453-462.

4. Fujak A, Raab W, Schuh A, et al. Natural course of scoliosis in proximal spinal muscular atrophy type II and IIIa: descriptive clinical study with retrospective data collection of 126 patients. BMC Musculoskelet Disord. Oct 4 2013;14:283.

5. Di Pede C, Salamon E, Motta M, et al. Spinal bracing and lung function in type-2 spinal muscular atrophy. Eur J Phys Rehabil Med. Apr 24 2018.

6. Garg S. Management of scoliosis in patients with Duchenne muscular dystrophy and spinal muscular atrophy: A literature review. J Pediatr Rehabil Med. 2016;9(1):23-29.

7. Stolte B, Totzeck A, Kizina K, et al. Feasibility and safety of intrathecal treatment with nusinersen in adult patients with spinal muscular atrophy. Ther Adv Neurol Disord. 2018;11:1756286418803246.

8. Bladen CL, Thompson R, Jackson JM, et al. Mapping the differences in care for 5,000 spinal muscular atrophy patients, a survey of 24 national registries in North America, Australasia and Europe. J Neurol. Jan 2014;261(1):152-163.

9. Burow M, Forst R, Forst J, et al. Perioperative complications of scoliosis surgery in patients with Duchenne muscular dystrophy and spinal muscular atrophy, focussing on wound healing disorders. Int J Neurosci. Jun 2017;127(6):479-485.

10. Chou SH, Lin GT, Shen PC, et al. The effect of scoliosis surgery on pulmonary function in spinal muscular atrophy type II patients. Eur Spine J. Jun 2017;26(6):1721-1731.

11. Holt JB, Dolan LA, Weinstein SL. Outcomes of Primary Posterior Spinal Fusion for Scoliosis in Spinal Muscular Atrophy: Clinical, Radiographic, and Pulmonary Outcomes and Complications. J Pediatr Orthop. Dec 2017;37(8):e505-e511.

12. Yang JH, Kasat NS, Suh SW, et al. Improvement in reflux gastroesophagitis in a patient with spinal muscular atrophy after surgical correction of kyphoscoliosis: a case report. Clin Orthop Relat Res. Dec 2011;469(12):3501-3505.

13. Bridwell KH, Baldus C, Iffrig TM, et al. Process measures and patient/parent evaluation of surgical management of spinal deformities in patients with progressive flaccid neuromuscular scoliosis (Duchenne’s muscular dystrophy and spinal muscular atrophy). Spine (Phila Pa 1976). Jul 1 1999;24(13):1300-1309.