Spinal Deformity Characteristics Associated With Intraspinal Anomalies in a Population of Presumed Adolescent Idiopathic Scoliosis (AIS)

INTRODUCTION: Intraspinal anomalies (IA) are reported to occur in 7% to 19% of patients undergoing surgery for adolescent idiopathic scoliosis (AIS). However, these studies have not focused on IA that require neurosurgical intervention and have not assessed whether deformity characteristics predict their underlying presence. We hypothesized that specific radiographic deformity parameters would be associated with underlying IA in a population of presumed AIS patients undergoing posterior spinal fusion (PSF). METHODS: A retrospective cohort study was performed over a 10-year period, identifying all patients with presumed AIS undergoing PSF who had a preoperative total spine MRI at a single, tertiary care pediatric hospital. The presence of an intraspinal anomaly was confirmed by MRI, and subsequent neurosurgical evaluation and intervention were recorded. Coronal and sagittal plane radiographic criteria were recorded, with a focus on previously identified predictive criteria. Radiographic criteria were compared against the whole population, as well as just those with thoracic deformities, seeking to identify factors associated with the presence of IA, as well as those associated with the need for neurosurgical intervention. RESULTS: A total of 427 patients met the inclusion criteria (mean 14.6±2.3 y, 80.7% female). Of these, 33 patients (7.7%) were diagnosed with an IA: 23 syringomyelia, 14 Chiari I malformation, 4 tethered spinal cord, and 8 cerebellar tonsillar ectopia, with only 8 patients (1.9%) undergoing neurosurgical treatment. Thoracic deformities were predominant in 350 patients (81.7%), which was statistically similar for IA and AIS (84.9% vs. 83.3%). For the whole cohort, a left thoracic curve apex was significantly more likely in a patient with an underlying IA (IA: 21% vs. AIS: 6.2%; P