Neuromuscular scoliosis (NMS) is the three-dimensional deformity of the spinal column that has a frontal plane curve greater than 10 degrees (Cobb angle >10 degrees) and is secondary to a neurological or muscular pathology.1
Idiopathic scoliosis is scoliosis of unknown etiology and is the most common form of scoliosis.2 In children with neurological or muscular conditions, NMS occurs much more frequently than idiopathic scoliosis. Etiologies can include central motor neuron involvement, peripheral motor neuron involvement, mixed motor neuron involvement, neuromuscular junction abnormality, or muscular causes (Table 1).
Table 1: Common Etiologies of Neuromuscular Scoliosis
|Central (Upper) Motor Nerve Involvement||Cerebral palsy, spinal cord trauma or tumor, hereditary ataxia (Friedrich’s), spinocerebellar ataxia, syringomyelia, encephalopathy, Rett syndrome|
|Peripheral Lower Motor Nerve Involvement||Acute anterior poliomyelitis, spinal muscular atrophy, hereditary motor and sensory neuropathy (Charcot-Marie-Tooth disease)|
|Mixed Central and Peripheral Nerve Involvement||Myelodysplasia, myelomeningocele, medullary lesion, tethered cord, amyotrophic lateral sclerosis|
|Neuromuscular Junction||Myasthenia gravis|
|Muscular Causes||Duchenne muscular dystrophy, Limb-girdle dystrophy, facioscapulohumeral dystrophy, arthrogryposis, congenital hypotonia, myotonic dystrophy|
Epidemiology including risk factors and primary prevention
The incidence of NMS among disorders that affect the central or peripheral motor nerves, neuromuscular junction, or muscles is between 25-100%, depending on the exact etiology (Table 2). In comparison, idiopathic scoliosis occurs in 2-4% of the general population. The incidence of NMS increases with severity of involvement and is inversely related to ambulation.
Table 2: Occurrence of Neuromuscular Scoliosis by Disease Process
|Diplegic cerebral palsy||25%|
|Lower lumber myelodysplasia||60%|
|Spinal muscular atrophy (SMA)||67%|
|Quadriplegic cerebral palsy||80%|
|Duchenne muscular dystrophy (DMD)||90%|
|Traumatic paralysis before the age of 10||100%|
Risk factors include any source of spinal imbalance. These may include spasticity, hypotonia, spinal asymmetry due to congenital bony malformation or asymmetrical growth (bony bridge, hemi-vertebrae), asymmetric strength or muscle tone, altered sensory feedback, or pelvic obliquity.
NMS results from an imbalance in control of trunk musculature around the spinal axis. This imbalance can be the result of many different sources (listed above). NMS is likely to progressively worsen due to the ineffective muscular compensations that initially led to the NMS. The classic radiographic finding in NMS is a long thoracolumbar curve with pelvic obliquity. Kyphotic deformity with trunk collapse is also commonly seen.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time):
NMS can present in all ages of children (typically before age 10 years) and trajectory is dependent on the disease process. In SMA and congenital myopathies, NMS can present very young and requires management beginning at initial detection. Conversely, in patients with DMD, NMS tends to be mild while a patient is ambulating but progresses once walking is lost. NMS is often progressive and can advance very rapidly. NMS can also continue to progress after skeletal maturity. Curve progression is seen in all curves once they reach 40 degrees. Treatment of the primary disease when available is important in prevention of the progression of NMS.
Specific secondary or associated conditions and complications
As NMS progresses and the angle of curvature becomes larger, general health and wellbeing decline. Progressive NMS affects ambulation, sitting balance, upper extremity positioning and function, and transfers. Comorbidities include pain, pressure sore formation, and alteration of ventilation mechanics and cardiopulmonary function. Progressive neurologic deterioration may occur due to spinal cord or peripheral nerve compression as a result of the deformity.3
Essentials of Assessment
History should include all events leading up to the current presentation, including diagnosis and work-up related to the underlying cause of NMS. It also requires a birth history, perinatal history, developmental milestones, family history, and inquiry regarding associated conditions such as renal or cardiac anomalies. It is important to review the growth rate, age at NMS diagnosis, progression rate of the curve, and detailed ambulation status, including both current and previous. An assessment of current cardiopulmonary status, pain, sitting balance, use of upper extremities, functional tasks, and use of adaptive devices or bracing should also be included.
Neurologic exam should include assessment of muscle tone, reflexes, balance, gait, walking capacity, motor strength, and sensory exam (especially in spinal cord injury patients).
Musculoskeletal exam should include joint range of motion (paying careful attention to the hip and pelvic positioning), shoulder symmetry and scapular position, pelvic tilt and obliquity, chest cage deviation, trunk balance, joint stiffness, joint deformity, limb length, and sitting balance.
Respiratory exam should include assessment of work of breathing, rib excursion and symmetry, and use of any assistive devices.
Cardiac exam should include rate and rhythm, pulses, evidence of edema.
Skin exam should include assessment for breakdown, pressure sores, or skin irritation.
Clinical functional assessment: mobility, self-care cognition/behavior/affective state
Functional status can be reported using Functional Independence Measures (FIM) and WeeFIM measures to report on self-care, mobility, and cognition. Activities of daily living (ADLs) are also used to assess function and independence. NMS does not affect cognition, however the underlying disease process may. Neuropsychological testing can provide further assessment of cognitive function if needed.
Laboratory studies are not required for NMS; however they may be completed based on underlying condition.
- The degree of scoliosis is measured using the Cobb angle. To measure the Cobb angle, lines are drawn (dashed line) along the superior endplate of the uppermost vertebrae involved to the inferior endplate of the lowest vertebrae involved. If the endplates cannot be reliably visualized, the borders of the pedicles are used instead (Figure 1). Interactive software can be used to calculate the Cobb angle.4
- Standing PA and lateral x-rays of the spine are the imaging of choice, but supine or sitting PA and lateral views can be obtained if patient is unable to stand.
- Supine lateral bend views can be used to assess stiffening of different spinal levels.5
- Antero-posterior views under asymmetric traction can assess reducibility of pelvic obliquity.
- Spinal MRI may detect any associated syrinx that may result in neurologic worsening.
- Thoracic CT can assess the caliber of the bronchi anterior the spinal convexity, as these are often reduced and are at risk for “bronchial stretching”.
- Renal ultrasound can be considered to assess bladder and kidneys if underlying condition is associated with abnormalities.
- Cardiac imaging can be considered to assess current cardiac function.
Recommend obtaining standing PA and lateral x-rays of the spine by age 5 or earlier with any exam concern for scoliosis. Repeat imaging should occur every 1-2 years for surveillance, and more frequently if there are concerns for progression. Refer to Orthopedic Surgery once curve reaches 20-30 degrees or with any rapid progression.
Supplemental assessment tools
Respiratory: pulmonary function tests (PFTs), use of any assistive devices (cough assist, intermittent positive pressure breathing devices (CPAP or BiPAP), non-invasive ventilation assists, or tracheostomy and ventilator use).
Cardiac: determined by underlying diagnosis, for example patients with a muscular dystrophy may benefit from a Holter monitor or preoperative intracavitary recording.
Additional assessments: nutritional assessment, swallowing assessment, and assessment for any chronic infections, for example chronic urinary tract infection.
Early prediction of outcomes
Predictors of NMS include the presence of a neuromuscular disorder, presence of hypotonia, previous hip surgery, intractable epilepsy, and female gender. New studies have also suggested ambulation status as a possible predictor, with non-ambulatory status linked to more severe disease impairment, worse curvature, and increased risk of complications.
Social role and social support system
As NMS progresses, it often is accompanied by a loss of independence through worsening sitting balance, decreased upper extremity usage, mobility device use including power wheelchairs, difficulty with self-care tasks including bathing and dressing – all of which increase caregiver demands. This can affect self-esteem, emotional health, and body image. It is important to refer to psychology and/or social work as needed for additional support.
Rehabilitation Management and Treatments
Available or current treatment guidelines
The Scoliosis Research Society (SRS) was started in 1966 with the goal to optimize care for all patients with spinal deformities. This organization continues to research and push the current practices in NMS treatment to improve patient outcomes. The International Scientific Society on Scoliosis Orthopedic and Rehabilitation Treatment (SOSORT) developed guidelines for idiopathic scoliosis that were renewed in 2011. However, there are no current guidelines for neuromuscular scoliosis. Although there is not one specific treatment guideline, the SRS and SOSORT recommendations are used in treatment planning worldwide.6
At different disease stages.
Bracing and seating modifications: The most conservative approach for management is bracing and seating modifications. The goal is to control the curve during periods of growth and delay surgical stabilization. Bracing and seat modifications may increase sitting stability, improve positioning and improve function.
Bracing is reserved for patients with smaller curves (typically between 25 to 40 degrees) and flexible curves.7 Bracing can be used in patients with spinal cord injuries with decreased or absent sensation through very close monitoring of the skin. Bracing must be done with caution in patients with DMD, SMA and those with pulmonary impairments as bracing may decrease chest expansion and exacerbate pulmonary concerns. Although some studies have shown bracing to be of more benefit on long C-shaped curves, the majority of curves secondary to NMS progress despite bracing and ultimately require surgery. Bracing may be used as long as it is improving functional tasks and not causing pain or skin breakdown. Bracing may provide some support and improve sitting balance and upper extremity functional positioning that together increase purposeful use of the arms.
Wheelchair and seating modifications may also improve function; modifications include trunk or cervical supports, head arrays, posterior contouring and custom seating to allow improved pressure distribution. Thoracolumbosacral orthoses (TLSO) have been shown to improve function and quality of life.
Surgical Stabilization: The goal for surgical management of NMS is to decrease pain, improve pulmonary and cardiac function, and improve ADLs, seat positioning, and self-perception. This is done through optimal correction of the spinal deformity as well as any pelvic obliquity (requires hardware to include the pelvis). Surgical correction is typically considered for patients with idiopathic scoliosis when a Cobb angle is over 40-50 degrees. In neuromuscular scoliosis, surgery may be considered in Cobb angles of 20-40 degrees if rapidly progressing. However, the risks of operative management of NMS are significant, with complication rates reported of up to 40% and may include surgical site infection, dural tear, paralytic ileus, hemorrhage, hematoma, sepsis, neurological deficit, implant failure, fracture, aspiration, pneumonia, respiratory failure, deep vein thrombosis, pulmonary embolism, renal complications, and pain. A 0-7% mortality rate is also reported for this procedure. The increased complication and mortality rates are attributed to higher preoperative degrees of disability and comorbid conditions. However, despite the risk of complications, 85% of parents and caregivers are satisfied with the outcomes of surgical intervention.8 Determining when it is appropriate to proceed with surgery can be difficult. Ideally, surgery does not compromise ultimate lung volume and thoracic cavity size in a child who has not reached skeletal maturity. Further, candidates for surgery should be chosen based on severity and potential reducibility of deformity.
The major types of surgery are as follows:
- Spinal Fusion: Spinal fusion remains the gold standard surgical technique to correct scoliosis in NMS and several long term studies have supported its use. Spinal fusion typically occurs after skeletal maturity to minimize the impact on the final size of the ribcage as spinal growth is inhibited following a fusion. Instrumentation during spinal fusion typically extends to the pelvis to correct any pelvic obliquity present. Extension of instrumentation to the pelvis with iliac screws has been shown to improve function when compared to fusions that did not extend to the pelvis. A spinal fusion can be performed by a combined anterior and posterior approach, or posterior only approach depending on the severity and flexibility of the curve. The combined approach has a greater complication rate. The extent of instrumentation can lead to spinal stiffness and make some hand to mouth activities more difficult, limit bending/reaching, and make self-catheterization more difficult. Despite these changes, surgery has been shown to substantially improve overall quality of life for both patients and caregivers.
- Non fusion techniques: Recently, more research has been done to explore non fusion techniques that permit growth.
- Growing Rods: Growing rods are a surgical alternative to bracing in young children and can be placed in children as young as 8 months. The goal with growing rods is to obtain a strong fixation on either side of the curve and, as the child grows, to repeatedly lengthen the rods. This allows the child’s thoracic volume and lung volume to continue to expand with age until the patient is old enough for spinal fusion with the smallest residual curve and with the least pulmonary compromise. Some of these systems require repeated surgeries to lengthen the rods, while others use non-invasive technology with magnetics for growth. Mechanical complications are common and these children remain at risk for all other complications from surgery including surgical site infections. Following growing rods, fusion is eventually required and provides a more stable life-long correction.
- Minimally Invasive Surgery: The minimally invasive surgical approach was developed more recently as an alternative to the growing rods procedure. It involves the instrumentation anchored by hook claws distally to the pelvis by iliosacral screws. Studies have noted that fibrosis and spontaneous fusion often occurs around the implants and rods after the initial procedure, stabilizing the spine. This procedure has been associated with lower complication rates and does not require spinal fusion but is still being explored.
Coordination of care
The conditions associated with NMS typically have multiorgan involvement, therefore a care team that includes pediatricians, neurologists, geneticists, physiatrists, cardiologists, pulmonologists, surgical specialists, therapists, and psychologists can improve care through a multi-disciplinary care model of management.
Patient & family education
It is important to educate both the patient as well as the family about the expected clinical course, clinical features, and the genetics of the associated condition. In NMS, a discussion about the expectation for curve progression and the possibility of a multi-staged treatment approach that may include bracing and/or surgery is important. It is also critical to educate about possible limitations following fusion secondary to decreased flexibility and position change and how this may impact function (self-catheterization for example).
Measurement of Treatment Outcomes including those that are impairment-based, activity participation-based and environmentally-based.
In NMS, treatment outcomes are typically defined by degree of curve reduction, residual curve, and change in function following treatment. The change in function may be described through FIMs or WeeFIMs.
Translation into Practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
Clinical management of NMS requires early vigilance and continued screening in patients with high risk conditions from infancy to adulthood. It requires monitoring progression by radiographs and clinical exams as well as frequent discussions about goals of care, intervention options, and optimization of management. A multidisciplinary team approach offers the best comprehensive care for improving clinical outcomes by optimizing health before, during, and after treatment.
Cutting Edge/ Emerging and Unique Concepts and Practice
Advancements in surgical techniques as well as pre-operative, intra-operative, and post-operative management of these patients continue to improve care and outcomes. Intraoperative monitoring is now used routinely for the reduction and prevention of neurologic complications.
Advancements in non-surgical techniques include custom molding, which still requires more research.
Further, serial casting, an older treatment, has reemerged due to complications associated with surgery.9
Gaps in the Evidence-Based Knowledge
As mentioned earlier, research is still needed to evaluate the usefulness of newer techniques including, but not limited to, minimally invasive surgical correction and custom molding. There is also a need for more research regarding optimal time for treatment initiation, optimal time for different surgical and nonsurgical interventions, and how to combine these modalities. Finally, while advancements have been made, there continues to be a high rate of complications associated with these patients. Further research is needed to help reduce these rates in the pre-op, intra-op and post-op periods.
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Original Version of the Topic
Andrea Paulson, MD. Neurogenic Scoliosis. 9/7/2018
Monis Syed, MD
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Sarah Macabales, DO
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Larissa Pavone, MD
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