1.1 Prevalence

The prevalence of NMS varies significantly across different neuromuscular conditions, reflecting the extent of nerve and muscle involvement characteristic of each condition. The prevalence of scoliosis in children with cerebral palsy (CP) can be quite high, especially in those with more severe forms of the disorder. Studies have shown that scoliosis affects approximately 25 % of children with CP who are ambulatory (able to walk), and the prevalence of scoliosis increases to approximately 60 % in those who are non-ambulatory.⁸ The risk of developing scoliosis further increases with the severity of CP, reaching up to 80 % in children with spastic quadriplegia.⁹ Almost all patients with Duchenne muscular dystrophy (DMD) develop scoliosis once they become wheelchair-bound if not treated with systemic glucocorticoids.⁹ Howard et al.¹⁰ reported that the prevalence of untreated DMD can approach 90 %, indicating a very high likelihood of spinal deformities as the disease progresses. The incidence of spinal muscle atrophy in patients with scoliosis varies with the type of spinal muscle atrophy but is generally high. For instance, Ruythooren et al.¹¹ reported that patients with type 2 and type 3 spinal muscle atrophy, who typically have a longer lifespan than patients with type 1 atrophy, have a high incidence of scoliosis, reported in approximately 67 % of cases.

Friedreich’s ataxia and myelodysplasia also show high incidences of scoliosis. Approximately 80 % of individuals with Friedreich’s ataxia develop scoliosis, likely due to the combined effects of neurological and muscular impairments.¹² The prevalence of myelodysplasia varies with the level of spinal involvement; lower lumbar involvement results in a 60 % incidence rate, which increases to 100 % for those with thoracic-level involvement, indicating a severe predisposition to spinal deformities.¹³ For patients who suffer from traumatic paralysis before the age of ten, the development of scoliosis is inevitable, with a 100 % incidence rate.¹⁴ This statistic is particularly alarming and calls for early and aggressive management strategies to address the spinal deformities that will undoubtedly develop.

1.2 Etiology

NMS is caused by a variety of neurological and muscular disorders that impact the ability of muscles to maintain proper spinal alignment. The development of NMS is closely linked to the underlying neuromuscular conditions, which can be influenced by genetic, developmental, and sometimes environmental factors.1.Neurological Disorders: Conditions such as cerebral palsy, traumatic spinal cord injury, and pregnancy affect the ability of the brain and spinal cord to communicate effectively with muscles, leading to imbalances that cause the spine to curve.¹⁵ For instance, cerebral palsy results from brain damage that occurs early in life and significantly affects muscle control and coordination.¹⁶ The severity of impairment in cerebral palsy patients is often classified using the Gross Motor Function Classification System (GMFCS), where higher levels indicate greater disability and an increased likelihood of developing scoliosis.¹⁷.2.Muscular Disorders: Diseases, such as DMD and spinal muscular atrophy, degrade muscle strength and function over time. DMD, an X-linked condition predominantly affecting males, leads to progressive muscle weakness that usually necessitates wheelchair use as the disease progresses, significantly heightening the risk of scoliosis.¹⁸ According to Suthar et al.,¹⁹ genetic disorders such as DMD involve mutations leading to muscle degeneration, which significantly influence the development of scoliosis. This connection highlights the importance of genetic predisposition in NMS.3.Genetic and Developmental Factors: Genetic disorders like Friedreich’s ataxia and conditions like myelomeningocele (a form of spina bifida) also predispose individuals to NMS. Friedreich’s ataxia, which leads to impaired muscle coordination and movement, has a direct impact on spinal alignment.²⁰ The severity of scoliosis in spina bifida patients, as reported by Li et al.,²¹ is closely related to the level of the spinal lesion, with higher lesions presenting greater risks of developing scoliosis. Developmental issues, such as those seen in spina bifida affect the spine's structural integrity, leading to higher instances of scoliosis.²².4.Environmental Factors: While less significant in NMS compared to idiopathic scoliosis, environmental factors like physical trauma or conditions leading to prolonged immobility can exacerbate the risk of developing scoliosis in individuals predisposed due to neuromuscular conditions.^1,4.

1.3 Diagnosis

The diagnosis of neuromuscular scoliosis involves several key assessments to identify and evaluate the extent of the spinal curvature attributable to neuromuscular conditions.¹⁴. The initial screening method typically includes the Adams forward bend test, which is performed with a scoliometer during a physical exam. This test helps to identify any asymmetry in the rib cage that may indicate vertebral rotation, commonly associated with scoliosis.²³. For more precise measurements, posteroanterior (PA) and lateral radiographs are preferred. These images are ideally taken while the patient is in a weight-bearing position to accurately assess the effects of gravity on the spine.^14,24.

For patients who are non-ambulatory, seated weight-bearing images are recommended, although obtaining these images can be challenging. If necessary, supine PAs and lateral films are used along with bending and traction films to help assess flexibility and the extent of curvature.^2,25.

Advanced imaging may be required for detailed surgical planning or in patients where congenital abnormalities or tumors are suspected. These methods include computed tomography (CT) scans for structural evaluation and magnetic resonance imaging (MRI) for detailed visualization of soft tissues, especially when early-onset scoliosis is diagnosed or when there is abnormal progression or pain that necessitates a deeper investigation into spinal and neurological structures.^2,3.

Two specific diagnostic tools mentioned are the Cobb angle and Risser index:•Cobb Angle: This is used to quantify the degree of scoliosis visible on radiographs by measuring the angle of spinal curvature. This measurement is critical for determining the severity of the curve and for tracking its progression over time.⁴.•Risser Index: This index assesses skeletal maturity based on the ossification of the iliac apophysis. It is a graded scale from 0 to 5, which helps clinicians understand the growth potential remaining in the spine, important for planning treatment timelines and interventions.^26,27.

Two specific diagnostic tools are the Cobb angle and the Risser index:•Cobb angle: This angle is used to quantify the degree of scoliosis visible on radiographs by measuring the angle of spinal curvature. This measurement is critical for determining the severity of the curve and for tracking its progression over time.⁴.•Risser index: This index assesses skeletal maturity based on the ossification of the iliac apophysis. The NRS is a graded scale from 0 to 5 that helps clinicians understand the growth potential of patients remaining in the spine and is important for planning treatment timelines and interventions.^26,27.

1.4 Management of neuromuscular scoliosis

Management strategies for NMS include both operative and nonoperative treatment modalities. Nonoperative management often serves as a temporary measure until surgery becomes necessary, while operative management aims at long-term stabilization and correction of the deformity.¹⁴. The following table (Table 1) represents a summary of both operative and nonoperative treatment options for different types of NMS:

2.1 Surgical techniques and equipment

Recent advancements in surgical techniques for neuromuscular scoliosis (NMS) have focused on minimizing the invasiveness and enhancing the effectiveness of interventions. Techniques such as the use of magnetically controlled growing rods (MCGRs) have become more prevalent. These rods allow for noninvasive postoperative adjustments, which are particularly beneficial in managing early-onset scoliosis by accommodating spinal growth and reducing the need for repeated surgeries.³⁰ Additionally, the development of fusionless surgery techniques, such as vertebral body tethering, represents a paradigm shift in treating adolescent idiopathic scoliosis and is being explored for its applicability in NMS. These techniques aim to preserve spinal mobility by preventing fusion, thus maintaining more natural spine biomechanics.³¹.

2.2 Genetic therapies

The role of genetic therapies in NMS is an area of burgeoning research. Ongoing studies are examining how targeted genetic interventions could mitigate the underlying muscular or neurological pathologies that contribute to scoliosis development.³². Although still in the early stages, this research holds promise for fundamentally altering the treatment landscape of NMS by addressing its root causes rather than just its manifestations.³³.

2.3 Role of technology

Robotic surgery and new imaging techniques are needed to improve surgical outcomes in patients with NMS. Robotic-assisted surgeries provide increased precision and consistency, potentially lowering the rates of complications and improving the accuracy of implant placement. This approach is particularly beneficial in complex spinal surgeries required for NMS patients, where precision is crucial for optimal outcomes.³⁴. Moreover, advanced imaging techniques continue to evolve, offering clearer and more detailed visualizations of spinal structures, which significantly aid in preoperative planning and intraoperative navigation. These advancements not only enhance surgical accuracy but also contribute to safer, more effective procedures with better patient outcomes.³⁵.

Together, these innovations mark a significant forward leap in the management of neuromuscular scoliosis, with ongoing research likely to introduce even more improvements in the near future.