ObjectiveRecently, 3‐Tesla magnetic resonance imaging (MRI) with intravenous gadolinium injection has been used to reveal endolymphatic hydrops (EH). In the present study, we aimed to evaluate EH in patients with Meniere's disease (MD) objectively and quantitatively, and compared the endolymphatic space (ELS) in individuals with MD and healthy controls, to gain understanding of the characteristics of MD.MethodsEighty‐two patients with unilateral MD (uMD), 16 patients with bilateral MD (bMD), and 47 healthy volunteers were enrolled. All participants underwent 3‐T MRI at 4 hours after intravenous gadolinium injection. The volumes of the total fluid space (TFS) and ELS were measured semiautomatically using our workstation, and the percentage of ELS to TFS (ELS percentage) was calculated.ResultsThe ELS percentage was 13.9 in the ears of controls, 18.2 in the contralateral ear of individuals with uMD, 26.1 in the affected ears of these individuals, and 23.0 in both ears of individuals with bMD. The ELS percentages in the affected ear of uMD and the ears of bMD individuals were significantly higher than that in the ears of control individuals (P < .01, one‐way analysis of variance (ANOVA), Tukey's test).ConclusionThe ELS is significantly larger in the affected ears of uMD and in both ears of bMD individuals. Accurate diagnosis of MD can be facilitated by using 3‐T MRI 4 hours after intravenous gadolinium injection and performing volumetric measurements of the ELS.Level of Evidence2b

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Meniere's disease is a common disease, that presents with recurrent vertigo and cochlear symptoms. The pathology of Meniere's disease was first reported to involve endolymphatic hydrops in 1938. The endolymphatic sac is thought to have a role to keep the hydrostatic pressure and endolymph homeostasis for the inner ear. As a surgery for intractable Meniere's disease, endolymphatic sac drainage with intraendolymphatic sac application of large doses of steroids is performed to control the endolymphatic hydrops and preserve or improve inner ear function. In the present study, to observe the effect of this surgery, we calculated the endolymphatic space size using 3-Tesla magnetic resonance imaging (MRI) 4 h after intravenous injection of gadolinium enhancement at two time points: just before surgery and 2 years after. To reveal the condition of the endolymphatic space, we constructed three-dimensional MR images semi-automatically and fused the three-dimensional images of the total fluid space of inner ear and the endolymphatic space. After fusing the images, we calculated the volume of the total fluid space and endolymphatic space. Two years after surgery, 16 of 20 patients (80.0%) showed relief from vertigo/dizziness and reductions in the ratio of the volume of the endolymphatic size to the total fluid space of inner ear. Endolymphatic sac drainage with intraendolymphatic sac application of large doses of steroids could control vertigo/dizziness and decrease the endolymphatic hydrops. These results indicate that endolymphatic sac drainage is a good treatment option for patients with intractable Meniere's disease. In addition, volumetric measurement of inner ear volume could be useful for confirming the effect of treatments on Meniere's disease.

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Modulation of the soleus H-reflex following galvanic vestibular stimulation (GVS) has been used to evaluate vestibulospinal tract function. It is not known whether this modulation is because of vestibular stimulation and/or cutaneous stimulation, and the suitable stimulating intensity of GVS for the modulation is not established. We investigated the influence of GVS intensity and cutaneous stimulation on the soleus H-reflex in healthy adults. We applied cathodal GVS (at 1, 2, and 3 mA) or 3-mA cutaneous stimulation as a conditioning stimulation in a random order to 17 individuals in the prone position with the head facing forward, and we examined the changes in the right soleus H-reflex amplitude. We maintained the interval between the conditioning stimulation's onset and the tibial nerve stimulation evoking the soleus H-reflex constant at 100 ms. The amplitude of all conditioned H-reflexes was significantly larger than that of the unconditioned H-reflexes. The greatest facilitation of the H-reflex occurred when 3-mA GVS was applied. The degree of facilitation of the H-reflex by 3-mA GVS was significantly larger than that produced by the 3-mA cutaneous stimulation. These findings indicate that (a) the facilitation of the soleus motor neuron pool excitability by GVS is derived from both vestibular stimulation and cutaneous stimulation, and (b) the intensity of GVS affects the degree of facilitation. When this technique is used to examine vestibulospinal tract function, no less than 3 mA GVS may be appropriate as the conditioning stimulation.

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