Neurogenic Scoliosis

Disease/Disorder

1. Definition

Neurogenic scoliosis (NS) is the three-dimensional deformity of the spinal column with a frontal plane curve greater than 10 degrees (Cobb angle >10 degrees), which is secondary to a neurological or muscular pathology.

2. Etiology

Idiopathic scoliosis is the most common form of scoliosis. In children with neurological or muscular pathology, NS 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.

Common Etiologies of Neurogenic 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), hereditary motor and sensory neuropathy
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

3. Epidemiology including risk factors and primary prevention

The incidence of NS among disorders that affect the central or peripheral motor nerves, neuromuscular junction, or muscles, is between 25-100%, depending on the exact etiology. This is in comparison to idiopathic scoliosis that occurs in 2-4% of the general population. The incidence of NS increases with severity of involvement and is inversely related to ambulation.

• Occurrence of Neurogenic Scoliosis by Disease Process
• Diplegic cerebral palsy: 25%
• Lower lumber myelodysplasia: 60%
• Spinal muscular atrophy (SMA): 67%
• Friedrich’s ataxia: 80%
• Quadriplegic cerebral palsy: 80%
• Duchenne Muscular Dystrophy (DMD): 90%
• Traumatic paralysis before the age of 10: 100% of people.

Risk factors include any source of spinal imbalance. These may include: spasticity, hypotonia, spinal asymmetry due to congenital boney malformation or asymmetrical growth (bony bridge, hemi-vertebrae), asymmetric strength or muscle tone, altered sensory feedback or pelvic obliquity.

4. Patho-anatomy/physiology

NS results from an imbalance in the control of trunk musculature around the spinal axis. This imbalance can be the result of many different sources (listed above). NS is likely to progressively worsen due to the ineffective muscular compensations that lead to the NS initially.  The classic radiographic finding in NS is a long thoracolumbar curve that includes the pelvis, including pelvic obliquity. It is also common to see kyphotic deformity with trunk collapse.

5. Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time):

NS 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, NS can present very young and needs to be managed starting from initial detection.  Conversely, in patients with DMD, NS tends to be minor while a patient is ambulating but progresses once walking is lost. NS tends to be progressive and can advanced very rapidly. NS can also continue to progress after skeletal maturity, especially thoraco-lumbar curves. Curve progression is seen in all curves once they reach 40 degrees.

6. Specific secondary or associated conditions and complications

As the NS progresses and the curve becomes larger general health and wellbeing decline. Progressive NS affects ambulation, sitting balance, upper extremity positioning and function, and transfers, and can to cause pain, lead to decubiti, and alter ventilation mechanics and cardiopulmonary function.

2. Essentials of Assessment

1. History

History should include the current diagnosis (if one has been identified) as well as the work up surrounding diagnosis and NS. It also requires a birth history, perinatal history, developmental milestones, family history, and inquiry regarding renal or cardiac anomalies. It is important to review the growth rate, age at NS diagnosis and progression rate of curve, as well as the patient’s ambulation status, including both current and previous in detail (not just “walking” or “not walking”).  Lastly include an assessment of current cardiopulmonary status, pain, sitting balance, use of upper extremities, functional tasks and adaptive devices or bracing used.

2. Physical examination

Neurologic exam including: muscle tone assessment including hypotonia and hypertonia in various muscle groups, reflexes, balance, gait, walking capacity and motor strength in proximal muscle groups, sensory exam (especially in spinal cord injury patients)

Musculoskeletal exam including: joint range of motion (paying careful attention to the hip and pelvic positioning), pelvic obliquity, shoulder symmetry and scapular position, pelvic tilt, chest cage deviation, trunk balance, joint stiffness, joint deformity, limb length and sitting balance.

Respiratory exam including: work of breathing, rib excursion and symmetry, use of any assistive devices.

Cardiac exam including: rate and rhythm as determined by underlying diagnosis

Skin exam: looking for decubiti or skin irritation

3. 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. NS does not affect cognition, however the underlying disease process may. Neuropsychological testing can provide further assessment of cognitive function if needed.

4. Laboratory studies

Laboratory studies are not required for NS, however may be completed based on underlying condition.

5. Imaging

1. Lying or standing postero-anterior and lateral spine X-rays with Cobb angle measurement.
2. Specific “bending” views as needed to assess stiffening of different spinal levels.
3. Anterio-posterior views under asymmetric traction to assess reducibility of pelvic obliquity.
4. Spinal MRI to detect any associated syrinx that may result in neurologic worsening.
5. Thoracic CT to assess the caliber of the bronchi anterior the spinal convexity, as these are often reduced and are at risk for “bronchial stretching”.
6. Renal Ultrasound can be considered to assess bladder and kidneys if underlying condition associated with abnormalities.
7. Cardiac imaging can be considered to assess current cardiac function.

Recommend obtaining first imaging by age 5 or earlier with any exam concern for scoliosis. Repeat imaging every 1-2 years for surveillance, more frequently with concerns or progression. Refer to Orthopedic Surgery once curve reaches 20-30 degrees or with any rapid progression.

6. Supplemental assessment tools

Respiratory: Pulmonary function tests (PFTs), use of any assistive devices (cough assist, intermittent positive pressure breathing devices (CPAP or BiPAP), or 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.

7. Early prediction of outcomes

Predictors of neuromuscular scoliosis include the presence of a neuromuscular disorder, presence of truncal tone, previous hip surgery, intractable epilepsy, and female gender.

8. Environmental

N/A

9. Social role and social support system

An NS 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 address these areas with psychology and social work.

10. Professional issues

There can be professional challenges and the possibility of ethical concerns as not all individuals or families will be interested in intervention for NS, including bracing or surgery.

C  Rehabilitation Management and Treatments

1. 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 NS treatment to improve patient outcomes. Although there is not one specific treatment guideline, their recommendations are used in treatment planning worldwide.

3. At different disease stages.

Bracing: 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 <40 degrees), flexible curves, and those with intact sensation. Bracing can be used in patients with spinal cord injuries even with decreased or absent sensation with very close monitoring of the skin.  Bracing must be done with caution in patients with DMD, SMA and those with pulmonary impairments as bracing can decrease chest expansion and exacerbate pulmonary concerns. The majority of curves secondary to NS progress despite bracing and ultimately require surgery. Bracing can be used for as long as it is improving functional tasks and not causing pain or skin breakdown.

Bracing can provide some support and improve sitting balance and upper extremity functional positioning that together increase purposeful use of the arms. Wheelchair and seating modifications can also improve function; modifications include trunk or cervical supports, head arrays, posterior contouring and custom seating to allow improved pressure distribution.

Surgical Stabilization: The goal for surgical management of NS 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). However, the risks of operative management of NS 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. The determination of when to proceed with surgery is trying to optimize the least severe and most reducible deformity without compromising ultimate lung volume and thoracic cavity size due to surgery prior to skeletal maturity. There are two major types of surgery, growing rods and spinal fusion.

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 are 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, 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 correction for a lifetime.

Spinal Fusion: Spinal fusion typically occurs after skeletal maturity to minimize the impact on the final size of the ribcage, because spinal growth is inhibited following a fusion. Instrumentation during spinal fusion typically extends to the pelvis to correct any pelvic obliquity present. This surgery can be performed by an anterior and posterior approach, or posterior only approach depending on the severity and flexibility of the curve. The anterior and posterior approach has a greater complication rate. The extent of instrumentation can lead to spinal stiffness and make some hand to mouth activities more difficult, can limit bending/reaching and make self-catheterization more difficult. Despite these changes, the overall quality of life has been showed to be substantially improved for both patient and caregivers.

3. Coordination of care

The conditions associated with NS 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.

4. 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 NS, 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, position change and how this may impact function (self-catheterization for example).

5. Measurement of Treatment Outcomes including those that are impairment-based, activity participation-based and environmentally-based.

In NS, 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.

6. Translation into Practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Clinical management of NS requires early vigilance from infancy to adulthood. It requires 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.

D. Cutting edge/emerging and unique concepts and practice

1.Cutting edge concepts and practice

Surgical techniques as well as pre-operative, intra-operative, and post-operative management of these patients continues to advance to improve care and outcomes. Intraoperative monitoring is now used routinely for the reduction and prevention of neurologic complications.

E. Gaps in the evidence-based knowledge

1.Controversies and gaps in the evidence-based knowledge

There continues to be research to try to optimize outcomes: when should treatment begin, when should different surgical and nonsurgical interventions be considered and in what order, and ways to minimize pre-operative, intra-operative, and post-operative risks to reduce complication rates.

Bibliography

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