Neuromuscular Scoliosis 

Updated: Feb 14, 2019
Author: Matthew B Dobbs, MD; Chief Editor: Jeffrey A Goldstein, MD 

Overview

Background

Scoliosis is a common deformity in many types of neuromuscular diseases. It is generally most severe in nonambulatory patients. Severe curves of the vertebral column cause difficulties in sitting.

Neuromuscular scoliosis can be defined as a coronal and sagittal plane deformity of the spine in patients with abnormalities of the myoneural pathways of the body. In neuromuscular spinal deformities, progression occurs much more frequently than in idiopathic scoliosis.

In addition, progression often continues into adulthood. The long-term effects of the spinal deformity in patients with neuromuscular conditions can be disabling. Loss of the ability to sit occurs, as does an accompanying decrease in overall function. In addition, pulmonary function is markedly affected.

Bracing neuromuscular curves does not affect the natural history of scoliosis and is not definitive treatment. Surgical stabilization constitutes the mainstay of treatment for neuromuscular scoliosis. Progressive curves require surgical correction and stabilization.

Pathophysiology

The pathophysiology is not well understood.[1] It seems logical to assume that scoliosis in these conditions is caused by muscle weakness, but this conclusion is difficult to support because some conditions are accompanied by spasticity and others by flaccidity. Furthermore, no consistent pattern of scoliosis is associated with a particular pattern of weakness.

Etiology

Scoliosis associated with neuromuscular disorders has been classified by the Scoliosis Research Society into neuropathic and myopathic types.

The neuropathic conditions have been subdivided into those with upper- and lower-motor-neuron lesions. The group with upper-motor-neuron lesions includes diseases such as cerebral palsy, syringomyelia, and spinal cord trauma; the group with lower-motor-neuron lesions includes poliomyelitis and spinal muscular atrophy. The myopathic conditions include arthrogryposis, muscular dystrophy, and other forms of myopathy.

Epidemiology

Because neuromuscular scoliosis has so many causes, the patterns and incidence vary greatly. However, the prevalence of spinal deformity in patients with a neuromuscular disorder is much higher than that in the general population. It ranges from 20% in children with cerebral palsy to 60% in patients with myelodysplasia. The prevalence rises to 90% in males with Duchenne muscular dystrophy. In general, the greater the neuromuscular involvement, the greater the likelihood and severity of scoliosis.

Prognosis

With care in surgical technique and adequate postoperative care, complications can be minimized. The patient can return to the preoperative functional level with a successful surgical result, which consists of a solidly fused spine in balance in the coronal and sagittal planes over a level pelvis.

Myung et al conducted a retrospective review of the use of posterior-only spinal instrumentation and fusion to the pelvis with iliac screws in 41 patients with neuromuscular scoliosis (mean age, 14 years).[2]  The fixation in the pelvis failed in 12 of the 41 (29%). No failures occurred if there were at least six screws in L5, S1, and pelvis (0/7); if there were fewer than six screws in L5, S1, and pelvis, the failure rate was 35% (12/34).

When traditional iliac screws with connectors to rods were used, all constructs had fewer than six screws in L5, S1, and pelvis.[2]  Only one failure occurred when S2 iliac screws were used, but that failure was without clinical consequence. The mean time from surgery to failure was 18 months (range, 1-49 months). The authors concluded that not placing bilateral pedicle screws at L5 and S1, in addition to two iliac screws, was associated with a 35% early failure rate of pelvic fixation.

Awwad et al conducted a retrospective analysis to evaluate the safety and efficacy of maximum-width segmental sacropelvic fixation to correct severe pelvic obliquity in 20 patients with neuromuscular scoliosis (mean age, 13 years).[3]  All 20 patients underwent spinal fusion with instrumentation extending to the pelvis; 14 underwent primary operations; and six had undergone previous spinal fusion above the pelvis requiring extension to the pelvis. The mean preoperative Cobb angle was 84° (range, 56-135°), corrected to 41° (range, 8-75°) postoperatively.

At the final follow-up, the mean spinal curve remained at 42° (range, 10-75°).[3]  The mean preoperative pelvic obliquity was 42° (range, 15-105°), which was corrected by 78% to 9° (range, 0-49°) postoperatively, with a pelvic obliquity of 10° (range, 2-49°) at final follow-up. The authors concluded that maximum-width segmental sacropelvic fixation, utilizing iliosacral screws and/or iliac screws, provides superior correction of severe pelvic obliquity in patients with neuromuscular scoliosis.

 

Presentation

History and Physical Examination

Evaluation of a patient with neuromuscular scoliosis entails a thorough assessment of all body systems. Accurate diagnosis of the underlying disease entity is essential and may require muscle biopsy.

Assessing nutritional status and pulmonary function is extremely important. The child's caregivers should be interviewed to gain an appreciation of the patient's functional level. The orthopedic examination includes assessment of all extremities and joints for contractures.[4]  Spinal deformity, decompensation, and shoulder balance are documented. Ambulatory status is also evaluated, and patients are classified as walkers, sitters, or nonsitters.

 

Workup

Laboratory Studies

Laboratory tests that may be helpful include the following:

  • Total lymphocyte count (should be >1500/μL) - Total lymphocyte count is one means of assessing nutritional status, which is extremely important because as many as one third of patients with neuromuscular conditions are malnourished; detecting and correcting malnutrition preoperatively helps prevent postoperative wound infection and healing problems
  • Hemoglobin - Assessing hemoglobin helps to determine nutritional status and whether a blood transfusion is likely to be needed
  • Total protein - Total protein is assessed to determine nutritional status
  • Albumin - Patients with serum albumin levels higher than 3.5 mg/dL have a much lower incidence of postoperative wound infection
  • Electrolytes - Electrolytes are assessed in the evaluation of nutritional status
  • Serum blood urea nitrogen (BUN) - This test is also useful in the assessment of nutritional status
  • Creatinine - Creatinine levels are used to assess nutritional status
  • Transferrin - An index using transferrin and albumin levels to identify malnourished patients has been developed

Radiography

Supine anteroposterior (AP) and lateral spinal radiographs are ordered for very young patients and older patients who cannot sit. Standing upright radiographs should be used for patients who can stand, and sitting radiographs should be used for patients who cannot stand. For the radiographs, standing patients do not support themselves with crutches, and sitting patients use no hand support. This gives an accurate depiction of the true magnitude of the spinal deformity under the effect of gravity and of pelvic obliquity and spinal balance.

The images below show a single patient in a photograph, an AP spinal radiograph, and a lateral spinal radiograph.

Neuromuscular scoliosis. Preoperative clinical pic Neuromuscular scoliosis. Preoperative clinical picture of a young male with severe scoliosis secondary to quadriplegic cerebral palsy.
Neuromuscular scoliosis. Preoperative anteroposter Neuromuscular scoliosis. Preoperative anteroposterior spinal radiograph of young male with severe scoliosis secondary to quadriplegic cerebral palsy.
Neuromuscular scoliosis. Preoperative lateral spin Neuromuscular scoliosis. Preoperative lateral spinal radiograph of young male with severe scoliosis secondary to quadriplegic cerebral palsy.

Traction spinal radiographs are obtained to evaluate the flexibility of the curves. These can be obtained in the radiology department with manual distraction with head halter and leg traction.

Other Tests

Patients capable of cooperating should be evaluated preoperatively with pulmonary function studies (see Surgical Therapy).

 

Treatment

Approach Considerations

The two main indications for surgery are as follows:

  • Curve progression
  • Deterioration in sitting ability

The main contraindication would be inability to tolerate the procedure. Preoperative assessment of respiratory competency, cardiac status, nutrition, possible feeding difficulties, seizure disorders, urologic status, and metabolic bone disease is necessary to ensure that the patient is healthy enough to tolerate surgery.

Medical Therapy

The goal of nonoperative treatment of patients with neuromuscular scoliosis is the same as that of operative treatment: to maintain the spine in a balanced position in the coronal and sagittal planes over a level pelvis. This goal is achieved with a custom molded thoracolumbosacral orthosis (TLSO) and molded seating supports. The aim is to control the curve during spinal growth rather than to correct the spinal deformity.

Controlling the curve during spinal growth may delay the need for surgical stabilization and is possible for most patients in the juvenile years. With the onset of the pubertal growth spurt, however, control of the curve is often lost, and surgical stabilization becomes necessary.[5]

Surgical Therapy

Surgical principles in the management of neuromuscular scoliosis differ from those in the management of idiopathic scoliosis. Fusion is necessary at a younger age, and the fused portion of the spine is longer. Fusion to the sacrum is fairly common because many of these children do not have sitting balance or have pelvic obliquity.[6]

Combined anterior-posterior fusion is common in the treatment of patients with neuromuscular scoliosis, either because posterior elements are absent, as in myelodysplasia, or because it is necessary to gain correction in a rigid lumbar or thoracolumbar curve and achieve a spine fused in balance over a level pelvis.[7, 8, 9, 10, 11, 12] The instrumentation used is segmental, comprising either a multiple hook-rod system, with or without the addition of sublaminar wires, or a Luque rod and sublaminar wires or a unit rod device. When fusion to the sacrum is necessary, it can be performed with the Luque-Galveston technique or with iliac screws.[13, 14, 15, 16, 17, 18, 19]

In patients requiring combined anterior-posterior spinal fusion, the issue of whether to perform these fusions as staged procedures or as same-day surgery remains unsettled. Combined anterior-posterior procedures facilitate spinal correction and yield a higher union rate in the neuromuscular population. The question of morbidity associated with same-day surgery vs that associated with staged procedures has not been fully resolved.[20]

In a study of 2154 neuromuscular scoliosis cases between 2002 and 2011, Rumalla et al reported a growth in the utilization of posterior-only fusion (from 66.2% to 90.2%) and a corresponding decrease in the use of combined anterior-posterior fusion (from 33.8% to 9.8%).[21]

In a systematic review and meta-analysis of seven studies (N = 602), Shao et al compared a combined anterior-posterior approach (APA) to neuromuscular scoliosis with a posterior-only approach (POA).[22]  POA was found to be comparable to APA with regard to correction of scoliosis in coronal and sagittal planes. APA had advantages with respect to correction of pelvic obliquity and decreasing the loss of angle between the postoperative period and follow-up; POA had advantages with respect to operating time, blood loss, duration of hospital stay, and complications.

Akbarnia et al reported on preliminary results using a magnetically controlled growing rod (MCGR) in children with progressive early-onset scoliosis. The study concluded that the technique was safe and provided results similar to that achieved with standard growing rods.[23]

Albert et al retrospectively reviewed the use of polyester bands and clamps utilizing pedicle screws in a hybrid fixation construct to treat neuromuscular scoliosis in 115 pediatric patients.[24] They concluded that this technique is an excellent adjunct in the correction of spinal deformity in these patients and that sublaminar bands in a hybrid construct are safe, achieve corrections equivalent to all-pedicle screw constructs, and may decrease potential complications associated with transpedicular fixation in patients with a highly dysmorphic and osteoporotic spine.

Funk et al retrospectively studied 80 patients treated with posterior spinal fusion to the pelvis for neuromuscular scoliosis, either with nonrigid constructs (>50% sublaminar wire fixation with Galveston or iliac screw pelvic fixation) or with rigid constructs (≥50% pedicle screw fixation with iliac or sacral alar iliac screw pelvic fixation).[25]  Patients in the rigid group had better deformity correction, lower pseudoarthrosis rates, and less need for anterior release; there were no significant differences in wound infection, wound dehiscence, implant prominence, or mechanical fixation failure.

Intraoperative monitoring has become a standard of care for spinal deformity surgeries. The combination of somatosensory and motor evoked potentials is widely accepted to be accurate and effective in detecting neurologic deficit in most patients during spine surgery. The success of this form of monitoring in the patient with neuromuscular scoliosis has been a matter of debate.[26]  The aforementioned study by Rumalla et al found intraoperative neurophysiologic monitoring to be growing in utilization and to be associated with a decrease in the complication rate.[21]

Intraoperative use of halo-femoral traction aids in the correction of pelvic obliquity and is becoming more widely adopted.[27]

Minimally invasive surgical approaches to neuromuscular scoliosis have been described.[28, 29, 30] Initial results suggested that such approaches have a number of benefits and few limitations; however, there is a need for further long-term data.

Preparation for surgery

To ensure that the patient can tolerate reconstructive spinal surgery, a detailed preoperative history and assessment should include an evaluation of respiratory competence, cardiac status, nutrition, possible feeding difficulties, seizure disorders, urologic status, and metabolic bone disease.[31]

Patients capable of cooperating should be evaluated with pulmonary function studies. Patients with vital capacities less than 30% of the predicted reference value may require postoperative ventilatory support. Performing formal pulmonary function testing is difficult in patients with neuromuscular scoliosis because patients are often unable to cooperate.[32]

Patients with Duchenne muscular dystrophy and Friedreich ataxia should be evaluated for cardiac involvement.[33]

Poor nutritional status is strongly linked to perioperative complications in these patients. Nutritional deficiencies should be corrected preoperatively through a forced nutritional improvement schedule or postoperatively with feeding tubes. Elective placement of gastric feeding tubes 3 months preoperatively dramatically improves nutritional status. The use of total parenteral nutrition (TPN) perioperatively also can help decrease problems with wound infections.[34, 35]

Operative details

Understanding the anatomy of the spine is crucial for safe and efficient exposure with a posterior approach. The incision is made from the spinous process above the most proximal vertebra to be instrumented to the most caudal extent of the proposed instrumented area. Identifying and staying in the midline is important so that muscle is not cut, which would lead to bleeding. The midline is identified by a thin line, which is actually the interspinous ligaments connecting the spinous processes.

Each vertebral level is exposed in a similar manner. An elevator is used to pull the soft tissue off of the spinous process, lamina, and transverse process of each respective level. To minimize blood loss, expose each segment completely the first time; do not leave soft tissue on the bone that will have to be removed later.

Intraoperative replacement of blood can be decreased with the use of a cell-saving device. The judicious use of blood products, including fresh frozen plasma and platelet and clotting factor replacements, can prevent disseminated intravascular coagulation.

Because inadequate iliac autograft is available in many of these operations, either because the iliac crest is small or because iliac fixation is used, graft augmentation with allograft or a bone graft substitute is required.

Malignant hyperthermia, characterized by muscular rigidity and increased body temperature, occurs with some frequency in certain neuromuscular disorders and is triggered by inhalational anesthetics and succinyl choline. This should be a consideration in all patients with neuromuscular conditions who are undergoing general anesthesia.

Postoperative Care

Postoperative care for these patients is demanding. Attention must be paid to pulmonary support, fluid status, and nutrition in addition to the elements of routine postoperative monitoring.[36]

Patients should be mobilized as rapidly as possible for a return to preoperative ambulatory and functional status. Because of the secure fixation obtained with segmental fixation systems and the lower functional demands of these patients, postoperative immobilization is rarely needed.

The postoperative images below depict the same patient previously shown in preoperative images (see Radiography).

Neuromuscular scoliosis. Postoperative clinical pi Neuromuscular scoliosis. Postoperative clinical picture of young male with severe scoliosis secondary to quadriplegic cerebral palsy.
Neuromuscular scoliosis. Postoperative anteroposte Neuromuscular scoliosis. Postoperative anteroposterior spinal radiograph of young male with severe scoliosis secondary to quadriplegic cerebral palsy at 2-year follow-up.
Neuromuscular scoliosis. Postoperative lateral spi Neuromuscular scoliosis. Postoperative lateral spinal radiograph of young male with severe scoliosis secondary to quadriplegic cerebral palsy at 2-year follow-up.

Complications

Because of the multitude of medical comorbidities of these patients, the complication rate after surgery is high. However, a report from the Scoliosis Research Society (SRS) Morbidity and Mortality database for neuromuscular scoliosis cases documented a 3.5-fold decrease in overall complication rates after spine surgery from 2004 to 2015.[37] Specifically, there were significant decreases in wound infections (superficial and deep), respiratory complications, and implant-associated complications.

Some postoperative complications are more common or significant than others, such as the following:

  • Respiratory problems
  • Ileus
  • Nutritional problems
  • Hip problems
  • Crankshaft phenomenon

Patients with neuromuscular scoliosis who have preexisting pulmonary compromise or experience greater intraoperative blood loss appear to be at higher risk for major complications after corrective surgery.[38]

Respiratory problems

A child with neuromuscular disease often has some degree of intercostal paralysis and a poor cough reflex. As a result, the incidence of postoperative pneumonia is high. To minimize this problem, attention to postoperative respiratory care is essential. It is common to leave the endotracheal tube in place for 1 or 2 days after the operation.

Ileus

Intestinal hypomotility may persist, necessitating prolonged parenteral support.

Nutritional problems

When intestinal motility returns postoperatively but the child cannot tolerate oral feedings, a feeding tube can be passed into the stomach or duodenum to allow nutritional support until oral feeding is tolerated.

Hip problems

Hip subluxation, dislocation, and contracture are frequent among patients who do not walk. Parents and caregivers should be told that the hip position might appear worse after the operation when contractures are present preoperatively. Gentle hip range of motion can be started postoperatively, but no stretching is allowed. These restrictions are in effect until the fusion is solid to avoid putting the sacral fixation in jeopardy.

Crankshaft phenomenon

Continued anterior spinal growth in the presence of a solid posterior fusion can occur in these children because many of them undergo fusion at a young age. Crankshaft phenomenon can be prevented with anterior fusion. However, the prospect of adding an anterior approach to an operation on a patient with respiratory compromise must be considered.

Long-Term Monitoring

The duration of the hospital stay is usually in the range of 7-10 days. Modifications in the child's wheelchair should be made as soon as possible to accommodate the new sitting position. The number of hours spent upright each day should be gradually increased.

The wound should be assessed 3 weeks postoperatively. Radiographs should be obtained 6 weeks postoperatively and again 3 and 6 months after surgery.