Natural course of scoliosis in proximal spinal muscular atrophy type II and IIIa: descriptive clinical study with retrospective data collection of 126 patients

Abstract

BackgroundProgressive scoliosis, pelvic obliquity and increasing reduction of pulmonary function are among the most significant problems for patients with SMA type II and SMA type III once they have lost the ability to walk. The aim of this study was to examine and document the development and natural course of scoliosis in patients with spinal muscular atrophy type II and IIIa.MethodsFor the purposes of a descriptive clinical study, we observed 126 patients, 99 with SMA II and 27 with SMA IIIa and the data of scoliosis, pelvic obliquity and relative age-dependent inspiratory vital capacity were evaluated.ResultsScoliosis and pelvic obliquity were regularly observed already in children under 4 years old in the group with SMA II. The severity and progression of both conditions were much more pronounced in the SMA II group than in the IIIa group. There was already a distinct reduction in relative vital capacity in the group of 4- to 6-year-olds with SMA II.ConclusionsThe differences between the two SMA types II and IIIa described in this study should be taken into consideration when developing new treatments and in management of scoliosis in the childhood years of these patients.

1st Italian SMA Family Association Consensus Meeting:

“…However, the severity of progression of scoliosis and pelvic obliquity seems more pronounced in SMA II than in SMA IIIa [44]. Studies on the course of pulmonary function after surgery for scoliosis are conflicting and seem to confirm a progressive decline in lung function despite spinal stabilization due to the progressive neuromuscular weakness associated with the disease [45].…”

Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care

“…As a consequence of poor trunk and thoracic muscular support, children with SMA have an increased incidence of thoracic insufficiency, the result of scoliosis and distortion of the rib cage [50,67]. Collapse of the ribs (similar to closing an umbrella) contributes to "parasol rib" deformity [53,54,[67][68][69]. Retrospective study of children with hypotonic scoliosis treated with either rib-or spine-based growth-friendly instrumentation systems have shown poor efficacy in ameliorating parasol rib deformity or increasing thoracic volume, and therefore are not recommended [67].…”

Emerging therapies and challenges in spinal muscular atrophy

“…In SMA types I and II, scoliosis occurs earlier and a more‐severe, progressive curvature is evident compared to SMA type III 30. Progression of scoliosis may exacerbate respiratory dysfunction, gastrointestinal reflux, and increase postural discomfort 30.…”

“…30 Progression of scoliosis may exacerbate respiratory dysfunction, gastrointestinal reflux, and increase postural discomfort. 30 Management of scoliosis includes nonsurgical options, such as physical therapy, bracing, and seating modification, and depending on the strategy used, may slow, but not necessarily prevent, curve progression. Additionally, surgical approaches are utilized in progressive scoliosis, most frequently in type II and III SMA.…”