Physicians classify the causes of scoliosis curves into one of two categories:
- Nonstructural scoliosis. Also known as functional scoliosis, this involves a spine that is structurally normal yet appears curved. This is a temporary curve that changes, and is caused by an underlying condition such as difference in leg length, muscle spasms or inflammatory conditions such as appendicitis. Physicians usually treat this type of scoliosis by addressing the underlying condition. The term nonstructural scoliosis has also been used to describe cases involving a side–to–side curvature.
- Structural scoliosis. This is a fixed curve that is treated individually according to its cause. Some cases of structural scoliosis are the result of disease, such as the inherited connective tissue disorder known as Marfan’s syndrome. In other cases, the curve occurs on its own. Other causes include neuromuscular diseases (such as cerebral palsy, poliomyelitis or muscular dystrophy), birth defects, injury, infection, tumors, metabolic diseases, rheumatic diseases or unknown factors. The term structural scoliosis has also been used to describe cases involving a twisting of the spine in three dimensions rather than a sideways curvature.
Certain factors are known to increase the risk for scoliosis, as well as the risk that the disorder will become more severe. These include:
- Sex. Girls ages 3 and older are more likely to have scoliosis than boys. In contrast, boys are more likely to have the disorder than girls before age 3.
- Age. The younger a child is when scoliosis begins, the more severe the condition is likely to become.
- Angle of the curve. The greater that angle of curve, the increased likelihood that the condition will get worse.
- Location. Curves in the middle to lower spine are less likely to worsen than those of the upper spine.
