Congenital Scoliosis
Definition and Classification
The term "congenital scoliosis" refers to a spinal deformity caused by vertebrae that are not properly formed. This occurs very early in development--in the first six weeks of embryonic formation and often before the mother knows she is pregnant, and the cause is not known. Congenital scoliosis does not seem to run in families. Genetic studies to date have not yielded much evidence that this condition can be inherited. Although congenital scoliosis is often discovered during the infant or toddler period, in some children it does not appear until their adolescent years.
Pediatric spine surgeons describe congenital spinal anomalies based on which part of the vertebra is malformed or connected. Depending on the structure of the anomaly, the child may exhibit scoliosis (a curve to the right or left), kyphosis (round back), or lordosis (sway back). However, not all congenital anomalies fit neatly into these categories. There are often elements of more than one deformity, particularly scoliosis and kyphosis occurring together.
Pediatric spine surgeons may refer to the spine anomaly as a "failure of segmentation." This means that one or more vertebrae are abnormally connected together on one side. This connection will slow growth on that side of the spine. Unopposed growth on one side with slowed growth on the other leads to a spinal deformity. "Failure of formation," the most common type of congenital problem, means that the normal shape of the vertebra is disrupted (Figure 2). On an anteroposterior radiograph (X-ray view taken from front to back) these vertebra will look like triangles instead of rectangles. Regular radiographs (X-rays), though, only show a two-dimensional representation of what is really a three-dimensional problem. The abnormally shaped vertebra may cause a wedge in the front, back, or either side, or a combination, tilting the spine at that level. Pediatric spine surgeons often use descriptive terminology to designate how much growth potential may be in the congenital anomaly. The term "fully segmented" indicates that there is a growth plate and a disk on both the top and bottom of the abnormal vertebra. "Semi-segmented hemivertebra" have a disk and growth plate either above or below. "Non-segmented hemivertebra" are fused to the vertebra above and below. Since non-segmented hemivertebrae have no growth plates, the curves they cause are much less likely to progress than those due to semi-segmented hemivertebrae, which are less likely to progress than a fully segmented hemivertebra. A "block vertebra" means that there is a missing disk space. Block vertebrae essentially have no growth potential and therefore rarely cause a progressive deformity.
Figure 2. Schematic drawing of the spine showing the classification of congenital anomalies.
In the thoracic (chest) part of the spine, congenital anomalies of the ribs often correspond with congenital anomalies of the vertebra. For example, an extra thoracic vertebra might attach to an extra rib. Vertebrae that are connected together may be associated with ribs that are connected together. The anomalies of the ribs and vertebrae are not always identical, but are often similar. A child with congenital spine anomalies often has more than one. This may be a congenital failure of formation on both the right and left sides of the spine or several grouped together or a mix of failure of formation and segmentation.
Evaluation
After the history and physical examination, the next step in evaluating congenital scoliosis is obtaining X-rays. Good quality anteroposterior and lateral X-rays are necessary. Radiographs of the neck should be taken to look for abnormal vertebrae in this region. The three-dimensional structure of the congenital anomaly may be best visualized on a CT scan with reconstruction (this study is usually done as part of a preoperative planning) (Figure 3). An MRI is very valuable to characterize the congenital anomaly and to be certain that there are no associated anomalies of the spinal cord. In children younger than 3 months (before the vertebrae ossify and harden), an ultrasound examination can scan the spinal cord for abnormalities without the need for sedation. Your pediatric spine surgeon may also advise your pediatrician to obtain an ultrasound of the kidneys or a cardiology consult. Because the kidneys and heart are formed at the same time as the vertebrae, something that affects the spine may likely affect the other organs. Children with congenital scoliosis have a 25% chance of having an anomaly in the urologic system (kidneys, bladder) or a 10% chance in the cardiac system. The child's limbs should be examined for any musculoskeletal abnormalities, such as a clubfoot or malformed hand/arm.
Figure 3. Three-dimension CT scan of the spine showing a hemivertebra (partially formed vertebra).
Prognosis
When your child's congenital spine anomaly is first diagnosed, no one will know exactly how much the spine deformity will progress as the child grows. There are some clues, however. Anomalies in the thoracic spine tend to progress more. Multiple fully-segmented hemivertebrae on the same side of the spine also tend to progress more. A hemivertebra opposite a set of fused vertebrae is the most likely combination to progress as the child grows. Because the most rapid period of spinal growth is in the first 5 years of life, and then at adolescence, these are the two times when the congenital curvature must be monitored most closely.