Laterality of fat distribution and its impact on tethered cord symptoms and surgical outcomes in pediatric spinal lipoma.

OBJECTIVE: The aim of this study was to evaluate whether MRI-based anatomical factors, including fat lateralization and spinal cord rotation, are associated with postoperative retethering in pediatric spinal lipoma. METHODS: This retrospective cohort study included pediatric patients (< 18 years old) who underwent spinal lipoma resection at King Chulalongkorn Memorial Hospital between 1999 and 2024, with a minimum follow-up of 12 months. Fat lateralization was graded on axial MRI based on the extent of lipomatous involvement relative to the dorsal and ventral nerve roots and dichotomized as nonlateralized (grades 0-1) or lateralized (grades 2-3). Spinal cord rotation was measured on axial MRI and categorized as < 20° or ≥ 20°. The cord-sac ratio (CSR) was classified as < 0.3, 0.3-0.5, or > 0.5. Associations with extent of resection and retethering were analyzed using appropriate statistical tests and Kaplan-Meier survival analysis. RESULTS: Eighty-six patients were included, with a mean follow-up of 9.7 years. Subtotal resection was significantly associated with spinal cord rotation ≥ 20° (p = 0.0003) and fat lateralization (p < 0.001). Both rotation and lateralization were correlated with higher CSR categories (p = 0.012 and p = 0.0095, respectively). Retethering occurred in 22.1% of patients and was significantly associated with cord rotation ≥ 20° (36.7% vs 14.3%, p = 0.028) and CSR > 0.5 (p = 0.0003). Extent of resection showed a trend toward lower retethering rates after total or near-total resection. Dorsal lipomas demonstrated the highest retethering rate, although this did not reach statistical significance. CONCLUSIONS: Preoperative MRI features, particularly spinal cord rotation and CSR, are important imaging markers associated with surgical complexity and postoperative retethering in pediatric spinal lipoma. Fat lateralization is strongly associated with limited extent of resection and unfavorable anatomy. Incorporating these anatomical parameters into preoperative assessment may improve risk stratification, surgical planning, and patient counseling.