Diagnostic Value of Flow-Void Sign for Localizing Ventral Dural Defects in Spine MRI

Ultrafast dynamic CT myelography and digital subtraction myelography are used to localize dural defects in spontaneous intracranial hypotension; however, their invasiveness and technical demands limit widespread availability. The "flow-void sign" on T2-weighted spine MRI has been proposed as a potential non-invasive marker of the ventral dural defect, but its clinical value remains unclear. This study aimed to evaluate the utility of the flow-void sign for predicting dural defect sites in ventral cerebrospinal fluid leaks.

This retrospective cohort study, using data from the headache registry at Seoul National University Hospital (March 2022-April 2025), included patients with ventral dural defects confirmed by ultrafast dynamic CT myelography or surgery. Three neurologists assessed the flow-void sign on T2-weighted spine magnetic resonance sequences and evaluated the spinal CT images for causative structural lesions. The concordance between the flow-void sign and ventral dural defect was analyzed using kappa statistics. Logistic regression analysis was performed to identify factors associated with this concordance.

Among 64 patients (57.8% female; median age, 40.0 years), the flow-void sign was observed in 43 (67.2%) patients. In the flow-void-positive group, 32 (74.4%) patients demonstrated concordance with the ventral dural defect level (κ=0.660, 95% confidence interval [CI], 0.476-0.825). The presence of a causative spinal lesion was significantly associated with the concordance (odds ratio, 6.48; 95% CI, 1.41-29.71; p=0.016).

The flow-void sign may provide an indirect clue for localizing a ventral dural defect and supplement the definitive imaging modalities.