Original ArticleThe vestibular aqueduct sign: Magnetic resonance imaging can detect abnormalities in both ears of patients with unilateral Meniere's disease
Introduction
Endolymphatic hydrops was first described by Hallpike and Cairns [1] as the foremost pathological change observed in patients with Meniere's disease (MD) in post-mortem studies, and by Naganawa and Nakashima [2] using single-dose intra-venous injections of gadolinium and delayed magnetic resonance imaging (MRI) acquisitions. Selective enhancement of the perilymphatic fluid, 4 hours after injection of gadolinium, allows the qualitative estimation of the endolymph area on labyrinthine slices. More recently, the presence of saccular endolymphatic hydrops has proved to be a valuable means of differentiating patients from healthy subjects [3], but only in patients with moderate or severe low-tone sensorineural hearing loss [4], [5].
However, altered distribution of the endolymph is not the only morphological modification of the temporal bone area in patients with MD. Previous histological studies have demonstrated atrophy of the endolymphatic sac, hypoplasia of the vestibular aqueduct (VA) and narrowing of the lumen of the endolymphatic duct in these patients [6], [7]. Similar findings have been highlighted with 2D computed tomography, 3D-Cone beam CT and with MRI [8], [9], [10] describing a correlation between the lack of a visible endolymphatic duct and the clinical course of MD. One hypothesis to explain VA modification relies on calcium ion (Ca2+) augmentation in hydropic ears, as demonstrated in biological samples [11], [12] and more recently with mineralized cells around the VA on pathological analysis [7]. In addition, controversies persist as to whether the abnormal [Ca2+] increase in endolymph is a secondary consequence of endolymphatic hydrops or its primary cause [12]. It is likely that changes in endolymph [Ca2+] contribute to functional losses found in the hydropic cochlea of animals, and possibly in the ears of humans with Meniere's disease.
The correlation between VA changes and saccular hydrops assessed by MRI has not been previously studied. Here, we performed a case-controlled study to obtain an overview of the normal vestibular aqueduct appearance on 3D-FLAIR sequences in healthy subjects and also to compare saccular hydrops imaging with variations in VA morphology.
We raise the hypothesis that VA abnormalities can be detected in the inner ear of patients with Meniere's disease in the absence of saccular hydrops.
Section snippets
Healthy subjects and patients
This single center parallel-group imaging study was registered with ClinicalTrials.gov (38RC14.428 for healthy subjects/38RC15.173 for patients) and was approved by our local ethics committee. Signed informed consent was obtained from all healthy volunteers and patients. MRI Data extracted from healthy volunteers have been previously reported [3], [5] and can be downloaded on an open source medical platform [13].
Twenty consecutive patients with a definite clinical diagnosis of unilateral MD
Vestibular aqueduct analysis
The VA was normal (grade 0) in 27 (67.5%) ears of the healthy subjects (Video 1 in Supplemental Material). In 8 healthy ears (20%) we found a discontinuous VA (grade 1) and in 5 healthy ears (12.5%) the VA was undetectable (grade 2) (Table 1).
In MD patients, the VA was normal (grade 0) in 5 ears (12.5%) while 16 ears (40%) and 19 ears (47.5%) had respectively discontinuous VA (grade 1) or non-visible VA (grade 2) (P < 0.001) (Video 2 in Supplemental Material).
In the symptomatic ears of MD
Discussion
Here we demonstrated that VA abnormalities were more frequent than saccular hydrops in MD patients, and were also found in asymptomatic ears (P < 0.001). We also showed that there was no added value of enhanced MRI sequences in the VA analysis.
Disclosure of interest
The authors declare that they have no competing interest.
The MRI scans for healthy subjects were funded by Guerbet SA ®.
The Grenoble MRI facility IRMaGe was partly funded by the French program “Investissement d’Avenir” run by the “Agence nationale pour la recherche” (grant number: ANR-11-INBS-0006).
Acknowledgments
We thank Dr Alison Foote (Grenoble Alps University Hospital) for critical editing.
In the memory of Patrice Jousse for the artworks.
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Endolymph magnetic resonance imaging: Contribution of saccule and utricle analysis in the management of patients with sensorineural ear disorders
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2020, European Annals of Otorhinolaryngology, Head and Neck DiseasesCitation Excerpt :The endolymphatic sac drains the endolymph through the vestibular aqueduct, as seen in the experimental model of endolymphatic hydrops developed by Kimura and Schuknecht, consisting in occluding the aqueduct [34]. In Menière's disease there is, moreover, a sharp reduction in aqueduct wall visibility on 3D-FLAIR sequences, reinforcing this theory of abnormal longitudinal flow [35]. Their study is especially interesting as the aqueduct wall lesion, presumed to involve calcification of chondroblasts as shown histologically [36] and on cone-beam CT [37], was bilateral in patients with clinically unilateral disease.