Pattern of Syringomyelia in Presumed Idiopathic and Congenital Scoliosis

STUDY DESIGN: Retrospective study. PURPOSE: This study was undertaken to compare the patterns of syringomyelia in patients with presumed idiopathic and congenital scoliosis. OVERVIEW OF LITERATURE: The incidence of neuraxial anomalies presenting as idiopathic scoliosis ranges from 2% to 14%; the common ones are idiopathic syringomyelia (IS) and Chiari malformation type 1 (CM1) with syringomyelia. Some authors have speculated that scoliosis is caused by the asymmetrical compression of anterior horn cells by a syrinx, which causes an imbalance of the trunk musculature. In congenital scoliosis, syringomyelia is the second commonest cord anomaly, and the deformity progression depends upon the underlying vertebral abnormality, the location of the abnormality, and the age of patient, and is independent of the intraspinal anomaly. METHODS: We analyzed the radiological records of 44 consecutive patients with scoliosis and syringomyelia. Of these 44 patients, 13 had IS, 12 had CM1, and 19 had congenital scoliosis. The radiographs were evaluated to determine the curve magnitude, sagittal alignment, side of convexity, and type of vertebral anomaly, if any. T1- and T2-weighted magnetic resonance imaging of the whole spine was analyzed to determine the presence of craniovertebral anomalies, syrinx length, syrinx diameter, and syrinx-cord ratio (SCR). RESULTS: The frequency of left convex curves was 26.1%, with no significant differences across the three groups. The mean length of the syrinx was 7.2±4.9 vertebral levels, and the mean SCR was 0.39±0.2. The mean syrinx length was significantly higher in patients with CM1 and IS, compared to patients with congenital scoliosis. The mean SCR was highest in patients with CM1. In congenital scoliosis, syringomyelia was seen most frequently in patients with a failure of formation, and 63.2% had concomitant cord anomalies. CONCLUSIONS: Syrinxes were smaller in size and length in patients with congenital scoliosis, and are distinct from those seen in IS and CM1.