Visualization of Nerve Pathology and Correlation with Clinical Severity in Bell Palsy Using 3D Double-Echo...

Bell 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 pathologic changes in the FN of patients with BP.

We retrospectively analyzed 30 patients with BP who underwent 3T MRI including 3D-DESS-WE within 30 days of onset and 60 sex- and age (SD, 2) matched controls. Qualitative evaluation of FN signal intensity (SI_FN) and thickness (TH_FN) was performed using a 3-point scale. Quantitative metrics included SI_FN and TH_FN measurements and affected-to-unaffected signal intensity and thickness ratios (SR_A/U and TR_A/U) 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 (CE) T1WI was assessed, and its agreement with 3D-DESS-WE-based qualitative assessment was evaluated.

Qualitative scores for SI_FN and TH_FN were significantly higher in the BP group than in controls (P < .001), with high interobserver agreement (κ = 0.810, 0.788, respectively). When dichotomized (score 0 versus 1-2), qualitative assessments showed good diagnostic performance with a sensitivity and specificity of 0.87 and 0.82 for SI_FN, and 0.90 and 0.80 for TH_FN, 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_FN and TH_FN were significantly higher on the affected side in the BP group (P < .001), whereas no significant lateral differences were observed in controls. Although SI_FN, TH_FN, and SR_A/U did not correlate significantly with clinical severity, TR_A/U was significantly inversely correlated with the Yanagihara score (r = -0.413, P = .02), which corresponds to a positive correlation with clinical severity. The Yanagihara score was the only independent predictor of TR_A/U in multiple regression analysis (β = -0.425, P = .04). Receiver operating characteristic analysis showed high diagnostic performance: area under the curve = 0.908 for SR_A/U and 0.927 for TR_A/U.

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