Correlating Vestibular Aqueduct and Temporal Bone Radioanatomy in Ménière's Disease patients and Controls: Analysis and Implications for Endolymphatic Sac Surgery

<b>Importance:</b> The anatomy of the vestibular aqueduct (VA) and its role in Ménière’s disease remain incompletely understood, yet its anatomical features are central to endolymphatic sac surgical surgery for intractable cases.<br><b>Objective:</b> To characterize the anatomical features of the VA and its relationship to surrounding structures, in controls and patients with severe Ménière’s disease using high-resolution computed tomography (CT).<br><b>Design, Setting, and Participants:</b> This retrospective study included 65 patients (128 ears) who underwent temporal bone CT scans. The Menière’s group consisted of 26 patients (51 ears) diagnosed according to AAO-HNS criteria, intractable despite maximal medical treatment. The control group included 39 patients (77 ears) undergoing CT for unrelated conditions.<br><b>Main Outcomes and Measures:</b> Measurements of VA and surrounding structures were analyzed and their correlations studied, then compared between the two groups. The following measurements were performed on each ear: A (VA thickness), B and B’ (VA width), C (distance between PSCC and meninges), D and D’ (PSCC depth), E and E’ (operculum depth). Reproducibility was assessed by intra- and inter-observer reliability tests, and k-means clustering was applied to classify anatomical variations.<br><b>Results:</b> All measurements, except A, showed significant intercorrelations. VA width (B) positively correlated with PSCC-meningeal distance (C) (r=0.683, p&lt;0.001) and negatively correlated with PSCC depth (D') (r= -0.290, p&lt; 0.01) and operculum depth (E') (r= -0.520, p&lt;0.001). Patients with narrow VA demonstrated reduced PSCC-meningeal distance and deeper operculum position relative to PSCC. Patients with Ménière’s disease exhibited significantly narrower VA and reduced distances between the posterior semicircular canal (PSCC) and the cerebellar dura compared to controls (p&lt;0.001). Cluster analysis identified three distinct anatomical patterns. 66.7% of Ménière’s patients vs 14.5% of controls belonged to the cluster exhibiting smaller VA dimensions, shorter PSCC-dura distance, and deeper operculum positions relative to the PSCC.<br><b>Conclusions and Relevance:</b> Narrow VA correlate with reduced PSCC-meningeal distance and deeper operculum position relative to PSCC. These anatomical variations may significantly challenge surgical approach for endolymphatic sac surgery. Patients with severe Ménière’s disease appear more likely to present this challenging anatomy.<br><b>Keywords </b>Vestibular Aqueduct, Endolymphatic Duct, Endolymphatic Sac, Meniere's Disease, Temporal Bone CT, Surgery, Anatomy, Radio-anatomy