Morphological correlation between caloric tests and vestibular hydrops in Ménière's disease using intravenous Gd enhanced inner ear MRI

<div><p>The purpose of this study was to prove the hypothesis that caloric response in Ménière's disease (MD) is reduced by hydropic expansion of the vestibular labyrinth, not by vestibular hypofunction, by evaluating the correlation morphologically using an intravenous Gadolinium (IV-Gd) inner ear MRI. In study I, the prevalence of abnormal video Head Impulse Test (vHIT) results among the patients with definite unilateral MD (n = 24) and vestibular neuritis (VN) (n = 22) were investigated. All patients showed abnormal canal paresis (CP) (> 26%) on caloric tests. The prevalence of abnormal vHIT in patients with abnormal CP was significantly lower in MD patients (12.5%) than that in VN patients (81.8%) (<i>p</i> < 0.001). In study II, morphological correlation between caloric tests and vestibular hydrops level was evaluated in unilateral MD patients (n = 16) who had normal vHIT results. Eleven patients (61%) had abnormal CP. After taking the images of IV-Gd inner ear MRI, the vestibular hydrops ratio (endolymph volume/total lymph volume = %VH) was measured. In addition, the relative vestibular hydrops ratio (%RVH = (%VHaffected ear—%VHunaffected ear) / (%VHaffected ear + %VHunaffected ear)) was calculated. Each ratio (%VH and %RVH) was compared with average peak slow phase velocity (PSPV) and CP, respectively. In the MD patients, %VH of the affected ear correlated significantly with mean PSPV on the same side (rs = -0.569, <i>p</i> = 0.024), while %RVH correlated significantly with CP (rs = 0.602, <i>p</i> = 0.014). In most MD patients (87.5%) compared to VN patients, vHIT results were normal even though the caloric function was reduced. In addition, the reduced caloric function with normal vHIT was related to the severity of the vestibular hydrops measured by the IV-Gd inner ear MRI. These findings concluded that the abnormal caloric tests with normal vHIT in MD indicated severe endolymphatic hydrops rather than vestibular hypofunction.</p></div

Scatter plots of the vestibular hydrops ratio and caloric response.

<p>X-axis represents caloric response which was defined as the average of peak slow phase velocity (PSPV) of nystagmus following warm and cold irrigation in each ear, while Y-axis represents the vestibular hydrops ratio. Results of scatter plots are shown in circle (●) for affected ears. rs, Spearman correlation coefficient; p, significance. An asterisk (*) indicates significant relationship.</p

MR cisternography (MRC) and HYDROPS2 imaging of two unilateral MD patients.

<p>MRC demonstrates regular anatomy of fluid filled spaces of the inner ears of subject 5 (a, d) and subject 11 (e, h). Both subject 5 (a-d) and 11 (e-h) have unilateral ear symptom on the right side and vestibular hydrops are observed in the affected ears (b, f). Additionally, asymptomatic vestibular hydrops in the affected side is observed in subject 11 (g, arrow).</p

Demographic characteristics of patients with definite unilateral Ménière's disease in Study II.

<p>Demographic characteristics of patients with definite unilateral Ménière's disease in Study II.</p

Vestibular hydrops ratio in affected and unaffected ears.

<p>Vestibular hydrops ratios (%VH) were measured to be 72.5% ± 21.8% in affected ears and 16.9% ± 19% in unaffected ears. An asterisk (*) indicates significant difference.</p