Four-hour-delayed 3D-FLAIR MRIs in patients with acute unilateral peripheral vestibulopathy

Abstract

Objective: Conventionally, MRI aids in differentiating acute unilateral peripheral vestibulopathy/vestibular neuritis (AUPV/VN) from mimickers. Meanwhile, the diagnostic utility of MRIs dedicated to the inner ear remains to be elucidated for diagnosing AUPV/VN.

Methods: We prospectively recruited 53 patients with AUPV/VN (mean age ± SD = 60 ± 15 years, 29 men). Initial MRIs were performed with a standard protocol, and an additional axial 3D-fluid-attenuated inversion recovery (3D-FLAIR) sequence was obtained 4 h after intravenous injection of gadoterate meglumine. Abnormal enhancement was defined as a signal intensity that exceeded the mean + 2SD value on the healthy side. The findings of neurotologic evaluation and MRIs were compared.

Results: Overall, the inter-rater agreement for gadolinium enhancement was 0.886 (Cohen's kappa coefficient). Enhancement was observed in 26 patients (49%), most frequently in the vestibule (n = 20), followed by the anterior (n = 12), horizontal (HC, n = 8), posterior canal (n = 5), and superior (n = 3) and inferior (n = 1) vestibular nerves. In multivariable logistic regression analysis, the enhancement was associated with decreased HC gain in video head-impulse tests (p = 0.036), increased interaural difference in ocular vestibular-evoked myogenic potentials (p = 0.001), and a longer onset-to-MRI time span (p = 0.024). The sensitivity and specificity were 92.3% and 81.5%, respectively, with an area under the curve of 0.90 for predicting gadolinium enhancement.

Interpretation: Robust gadolinium enhancement was observed on 4-hour-delayed 3D-FLAIR images in nearly half of the patients with AUPV/VN, with a good correlation with the results of neurotologic evaluation. The positivity may be determined by the extent of vestibular deficit, timing of imaging acquisition, and possibly by the underlying etiology causing AUPV/VN. MRIs may aid in delineating the involved structures in AUPV/VN.

Figure 1

Quantitative evaluation of a degree of the perilymphatic enhancement. Six freehand round or polygonal regions of interests (ROIs) were set manually in AC (3.22–3.68 mm²), HC (6.90–9.39 mm²), PC (6.90–9.39 mm²), canalicular segments of the superior and inferior vestibular nerves (4.60 mm²), and vestibule (20.40 mm²) on 3D‐FLAIR sequence to include as much of the perilymph as possible. An additional 50 mm² circular ROI was drawn in the medulla at the same plane as the vestibule. The mean signal intensity was recorded for each ROI. The signal intensity ratios of the vestibular nerves and inner ear structure to that of the signal intensity of the medulla were calculated to avoid bias from patient‐related artifacts. AC, anterior canal; HC, horizontal canal; PC, posterior canal.

Figure 2

Comparison of gadolinium enhancement of each neural structure between the sides. Contrast enhancement was more prominent in the superior vestibular nerve (1.16 ± 0.21 vs. 1.09 ± 0.20, p = 0.027), vestibule (0.66 ± 0.23 vs. 0.47 ± 0.11, p < 0.001), HC (0.30 ± 0.13 vs. 0.22 ± 0.09, p < 0.001), and AC (0.48 ± 0.21 vs. 0.35 ± 0.13, p < 0.001) on the lesioned side than those on the healthy side (Fig. 2). However, no differences were found for the inferior vestibular nerve (1.14 ± 0.27 vs. 1.16 ± 0.23, p = 0.611) and PC (0.40 ± 0.16 vs. 0.36 ± 0.13, p = 0.168) between the sides.

Figure 3

Representative MRIs in patients with acute unilateral peripheral vestibulopathy/vestibular neuritis. (A) No signal changes are present on baseline 3D‐FLAIR image in a patient with right acute unilateral peripheral vestibulopathy/vestibular neuritis (upper row). Contrastingly, a robust gadolinium enhancement is observed in the horizontal canal (arrow) and vestibule on the 4‐hour‐delayed 3D‐FLAIR image (red rectangle; lower row). (B) gadolinium enhancement is found in the vestibule (arrowhead) on the 4‐hour‐delayed 3D‐FLAIR image (lower row) while showing no discernible changes on baseline 3D‐FLAIR image (upper row).

Figure 4

Receiver operating characteristic analysis for VOR gain, IAD of oVEMP, and onset‐to‐MRI for separating gadolinium enhancement from no enhancement on MRIs. The sensitivity was 92.3%, and specificity was 81.5% at cutoff values of 0.95 for HC gain, 100% for IAD of oVEMP, and 4 days for a time span from symptom onset to MRI with an AUC of 0.90 [95% CI = 0.82–0.98]. AUC, area under the curve; HC, horizontal canal; IAD, interaural difference; oVEMP, ocular vestibular‐evoked myogenic potentials; VOR, vestibulo‐ocular reflex.