Optimal Filum Terminale Thickness Cutoff Value on Sonography for Lipoma Screening in Young Children.

OBJECTIVES: The purpose of this study was to evaluate the normal thickness of the filum terminale on sonography and suggest an optimal cutoff value for filum terminale lipoma screening in young children. METHODS: We retrospectively reviewed lumbosacral sonograms and magnetic resonance images from children younger than 36 months that were obtained between January 2013 and June 2014. The filum terminale thickness on sonography and the presence of fat in the filum terminale on magnetic resonance imaging were evaluated. RESULTS: From 111 children (mean age ± SD, 3.6 ± 3.0 months), 49 did not have abnormal lesions (normal group), and 62 had fat infiltration in the filum terminale (lipoma group). The filum terminale was thicker in the lipoma group than the normal group (1.5 ± 0.5 versus 0.9 ± 0.2 mm; P < .001). Filum terminale thickness also showed significance in a multivariable analysis with sex and age (odds ratio per 0.1-mm unit, 2.754; P < .001) and in propensity score matching for age (P < .001). The optimal cutoff value for filum terminale lipoma screening was 1.1 mm, with 94% sensitivity and 86% specificity. CONCLUSIONS: The conventional cutoff value of 2 mm for a thickened filum terminale on sonography can be too thick. We suggest an optimal cutoff value of 1.1 mm for lipoma screening in young children.