Three common types of scoliosis can be found in children and adolescents; congenital scoliosis (which is present at birth), idiopathic scoliosis (which has no identifiable cause), and neuromuscular scoliosis (which is directly related to an underlying condition such as cerebral palsy and muscular dystrophy).
Neuromuscular scoliosis represents only a small segment of the total number of scoliosis cases diagnosed each year. However, the underlying disorders associated with this form of scoliosis often result in some of the more complex and extensive curves seen by orthopedic surgeons and present a unique set of treatment challenges.
As with idiopathic scoliosis, which constitutes the most common form of the disorder, neuromuscular scoliosis is diagnosed when there is the presence of a curve in the spine that measures greater than ten degrees. In contrast to patients with idiopathic scoliosis, in which the curve is restricted to a small section of the spine [see Figure 1], children with neuromuscular scoliosis develop long, sweeping S- and/or C-shaped curves that involve the entire spine, including the sacrum (the vertebrae that form part of the pelvis) [see Figure 2]. The curves seen in children with neuromuscular scoliosis are also much more likely to progress than those seen in idiopathic scoliosis.
"Also," explains Roger F. Widmann, MD, Chief of Pediatric Orthopedic Surgery at Hospital for Special Surgery (HSS), "children with neuromuscular scoliosis continue to be at risk for progression of their deformities into adulthood." Children with idiopathic scoliosis and curves that are less than 50 degrees generally do not progress upon reaching maturity.
Figure 1: X-ray of a patient with idiopathic scoliosis
Figure 2: X-ray of patient with neuromuscular scoliosis
As with other forms of scoliosis, x-rays of the spine are key tools in the diagnosis of neuromuscular scoliosis. Often, these patients are often unable to stand; therefore, the pediatric orthopedist obtains seated images to assess curve progression.
For some patients, braces may be recommended to help achieve sitting balance, thereby freeing the arms for other activities. Custom seating systems can also help accomplish this goal. Dr. Widmann notes, "It is important to understand that bracing will not slow the progression of the curve as it can in some other forms of scoliosis."
Surgical treatment of neuromuscular scoliosis is performed to stop the progression and correct the curve. As a patient’s pelvis is brought back to a more normal, level position, it can then provide a stable platform for sitting.
The pediatric orthopedic surgeon addresses the curve by realigning the bone using rods and bone grafts to fuse areas of the spine and maintain the correction. "For these patients, we almost always use allografts [freeze-dried, irradiated donor bone] with excellent results," says Dr. Widmann. Because patients with neuromuscular scoliosis often have poor bone density, a variety of techniques are used to fix the bone in place, including hooks, pedicle screws, and wires.
Timing of the surgery varies and may be dictated by the underlying disorder. "In the presence of muscular dystrophy, for example, we consider surgical intervention once the child is wheelchair-bound, since curve progression seems to be related to loss of ambulatory ability," Dr. Widmann explains.
A curve that is somewhat less than 40 degrees may also require surgery in patients with muscular dystrophy since the curve can be expected to progress in a predictable manner. In the presence of cerebral palsy, surgery may not be recommended until there is documented progression of the curve to 45 or 50 degrees and/or the child develops difficulty sitting or maintaining his/her balance.
Children who are surgical candidates must be screened carefully. At HSS, a multidisciplinary team of health care professionals ensures that the child has optimal breathing function and that safeguards are in place to prevent pneumonia and any potential difficulties with swallowing - risks that may be associated with the underlying disorder.
Because patients with neuromuscular scoliosis have an increased risk of blood loss during surgery, multiple techniques are used, including cell savers (machines that filter the blood so that it may be given back to the patient), the use of designated donor blood, or autologous blood (blood that the patient donates in advance of the surgery), if needed.
Figures 3 & 4 (top): Anterior (front) and lateral (side) x-rays of a patient with neuromuscular scoliosis before corrective surgery
Following surgery, many children with neuromuscular scoliosis remain for 1-2 days in the pediatric intensive care for acute respiratory management. In the majority of cases, one surgery is performed for correction of the curve, although, Dr. Widmann notes, some patients with very large curves may require a second procedure for additional releases and fusions.
Published: 12/6/2011Summary by Nancy Novick. Imaging courtesy of the HSS Department of Radiology and Imaging.