Age strongly influences the scoliosis angle, a recent study published in Neuromuscular Disorders has revealed.

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations in the survival motor neuron one gene (SMN1), resulting in weakness and muscle deterioration and subsequently leading to several orthopedic complications. Patients with type 2 SMA generally can sit without help from others, but they cannot walk independently and hence develop progressive scoliosis.

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Prior evidence has revealed new therapeutic options for treating type 2 SMA, which have improved motor and respiratory functions, the authors noted. Still, data on the rate of scoliosis progression has yet to be systematically reported because of the lack of information on the rate of progression in untreated patients, which makes it tough to determine possible differences between the treated and untreated patients, the study authors continued.

The research team conducted the study to retrospectively assess the onset and progression of scoliosis in a large group of patients with untreated type 2.

“More specifically, we wished to establish the onset of the first signs of scoliosis and the distribution of scoliosis angle in relation to a number of variables, including age, motor function, SMN2 copies and gender. In patients who had longitudinal assessments, we also aimed to compute the annual rate of scoliosis angle progression,” the authors wrote.

In their study, the research team recruited 84 patients with SMA type 2 between November 2007 and February 2022 with at least one scoliosis angle measured using Cobb’s angle method. The inclusion criteria for patients were based on those with a genetic diagnosis of SMA, having a clinical diagnosis of SMA type 2, and were not being treated with the approved disease-modifying treatments such as nusinersen, risdiplam, onasemnogene, and abeparvovec. 

Study results indicated that 54 of 84 patients experienced more than one scoliosis angle. The remaining 17 patients showed no scoliosis angle measured. Still, they did possess a record of clinical assessments indicating no clinical signs of scoliosis when they were seen with no indication for X-ray.

Moreover, the scoliosis angle considerably increased with the corresponding decrease in Hammersmith Functional Motor Scale Expanded (HFMSE) scores, indicating the association between the overall level of motor function and the magnitude of scoliosis in the whole cohort.

Additionally, study results confirmed the progression of scoliosis in patients with type 2 SMA , giving details of the progression associated with different variables such as age, gender, functional status, and scoliosis angle registered at baseline. Unsurprisingly, age was reported to have a strong influence on scoliosis angle. 

“Our data may be of help in the interpretation of the results to establish possible differences in the trajectories of progression between treated and untreated type II individuals,” the authors concluded.

Reference

Coratti G, Pera MC, et al. Long term follow-up of scoliosis progression in type II SMA patients. Neuromuscular Disorders. Published online November 17, 2022.