Diminished Spinal Cord Size Associated with Congenital Scoliosis of the Thoracic Spine*

Abstract

Intraspinal anomalies are common in patients with congenital scoliosis and are a known risk factor for neurological complications. Smaller but normal-appearing spinal cords have not been described in association with congenital scoliosis, nor have they been considered to be an anomaly with a similar neurological risk. We previously reported on small spinal cords associated with Klippel-Feil syndrome. We hypothesized that patients with congenital thoracic scoliosis would similarly have smaller spinal cords as compared with normal controls, with a potentially increased risk for myelopathy. We reviewed thirty patients with congenital scoliosis (including fifteen patients with failure of vertebral formation and fifteen with failure of vertebral segmentation). All patients had adequate axial T2-weighted, digitally formatted magnetic resonance imaging scans that were suitable for cross-sectional measurement. Cross-sectional areas of the spinal cord and spinal canal at each of the twelve thoracic levels were calculated three times by a blinded observer, and the average values were compared with measurements from age-matched normal controls. We observed a significantly smaller mean cross-sectional area at all levels of the spinal cord in the study group as compared with the control group (p < 0.01). When the pathological segments were evaluated, both with and without the inclusion of the adjacent normal segments, the spinal cord was smaller for the study group (p < 0.01). Within the study group, small spinal cords were observed in patients with failed vertebral formation as well as in patients with failed vertebral segmentation, but without an identifiable difference between these two subgroups. The spinal canal was also smaller for the patients in the study group, but not in all cases. No patient showed a reduction of, or encroachment on, the space available for the spinal cord. Spinal cord size increased with age in both the study group and the control group but remained consistently smaller in the study group. Within the study group, the presence of intraspinal anomalies did not appear to influence the spinal cord size. The spinal cord is significantly smaller in patients with congenital thoracic scoliosis than in normal controls. Because small spinal cords have been reported to be associated with neurological sequelae, we advise that the diminished spinal cord size be considered an important component of intraspinal anomalies associated with congenital scoliosis.