Visualization of Nerve Pathology and Correlation with Clinical Severity in Bell's Palsy Using 3D Double-Echo Steady-State with Water Excitation Sequence.

Background And Purpose: Bell's palsy (BP) is the most common cause of facial nerve (FN) palsy. This study aimed to investigate the diagnostic ability of the 3D Double-Echo Steady-State with Water Excitation (3D-DESS-WE) sequence to visualize pathological changes in the FN of BP patients.

Materials And Methods: We retrospectively analyzed 30 BP patients who underwent 3T MRI including 3D-DESS-WE within 30 days of onset and 60 sex-and age±2-matched controls. Qualitative evaluation of FN signal intensity (SI) and thickness (TH) was performed using a 3-point scale. Quantitative metrics included SI and TH measurements and affected-to-unaffected ratios (SR and TR) in the BP group, and right-to-left ratios in controls. Interobserver agreement, group comparisons, correlations with clinical severity (Yanagihara score), and diagnostic performance were assessed. In a subset of 17 matched pairs, the diagnostic performance of contrast-enhanced T1WI (CE-T1WI) was assessed, and its agreement with 3D-DESS-WE-based qualitative assessment was evaluated.

Results: Qualitative scores for SI and TH were significantly higher in the BP group than in controls ( < .001), with high interobserver agreement (κ = 0.810, 0.788, respectively). When dichotomized (score 0 vs. 1-2), qualitative assessments showed good diagnostic performance with sensitivity and specificity of 0.87 and 0.82 for SI, and 0.90 and 0.80 for TH, respectively. Neither qualitative score correlated significantly with clinical severity. Agreement between 3D-DESS-WE-based and CE-T1WI-based qualitative assessments was substantial to almost perfect (κ = 0.766-0.882). In quantitative analysis, both SI and TH were significantly higher on the affected side in the BP group ( < .001), whereas no significant lateral differences were observed in controls. Although SI, TH, and SR did not correlate significantly with clinical severity, TR was significantly inversely correlated with the Yanagihara score (r = -0.413, = .02), which corresponds to a positive correlation with clinical severity. The Yanagihara score was the only independent predictor for TR in multiple regression analysis (β = -0.425, = .04). ROC analysis showed high diagnostic performance: AUC = 0.908 for SR and 0.927 for TR.

Conclusions: 3D-DESS-WE may be a valuable tool for the routine clinical assessment of BP.

Abbreviations: 3D-DESS-WE＝3D Double-Echo Steady-State with Water Excitation; 3D-PSIF＝3D reversed fast imaging in steady-state free precession.