Features of Neuromuscular Scoliosis (Curved Spine)
The group of diseases under the category of muscular dystrophy share some common characteristics, i.e. muscular weakness, atrophy (wasting) and development of contractures of the limbs. When the same weakness affects the muscles of the spine, often with some imbalance or asymmetrical involvement, scoliosis of the spine (curved spine) can result.
Scoliosis is one of the common complications of patients with muscular dystrophy who are only able to sit (non-walkers). For Duchenne Muscular Dystrophy (DMD), the scoliosis commonly develop and progress rapidly after they become wheelchair bound. For patients with Spinal Muscular Atrophy (SMA) where there are different forms with different severity, spinal deformities develop much earlier in non-walkers than in ambulant patients. In both DMD and SMA patients, the spinal curvatures are often thoracolumbar in location. Wheelchairs adapted with a firm seat and support is useful towards delaying the onset of scoliosis. On the other hand, marked spinal curvature may also make seating impossible. Forestalling or prevention of this complication is not always possible for some patients particularly when their ability to walk is lost. Although special body braces (spinal orthoses) have been tried, these were found to be ineffective in the management of neuromuscular scoliosis.
It is important to recognize the onset of scoliosis as it hinders adequate respiratory (breathing) functions. A curved spine results in restriction in the movement of the thoracic cage and thus, adversely affects respiratory capabilities. When wheelchair bound, patients should be encouraged to use incentive spirometry to maintain their respiratory efforts for as long as possible.
The indication and the timing for the surgical/operative stabilization of the spine are dependent on the degree and progression of the scoliosis as well as the respiratory capabilities of the patient. For patients with DMD, the progression of scoliosis is rapid, and averages 10o for each year that the child is wheelchair bound. Early spinal stabilization is often indicated in patients with muscular dystrophy when the spinal curvature reaches 30o, before the onset of breathing difficulties make the surgery more risky. By 14 years of age, the functional vital capacity (breathing efforts) of patients with DMD is only about 50% of normal. The lowest safe limits for surgery requires a functional vital capacity of at least between 30 - 50%.
Pre-operatively, all patients with muscular dystrophy need to have a detailed assessment of their breathing capabilities including the determination of their blood oxygen and carbon dioxide levels. In addition, a cardiac (heart) evaluation is necessary for patients with DMD as there could be abnormalities or weakness of the cardiac muscles as well. Following a successful operation, good correction of the spinal curvature is possible, with resulting improvements in the respiratory status (breathing capabilities), sitting balance, quality of life and comfort for these patients.
Dr Ong Hian Tat
Paediatrician, National University Hospital