Severity of Endolymphatic Sac/Vestibular Aqueduct Hypoplasia Correlates with Sequence of Ear Involvement in Meniere’s Disease

Introduction: Approximately 30% of Meniere's disease (MD) patients present with concomitant hypoplasia of the endolymphatic sac (ES) and vestibular aqueduct (VA), designated MDhp. We hypothesized that: (a) ES/VA hypoplasia varies in severity within and between MDhp patients, reflecting developmental arrest at different time points; and (b) greater hypoplasia severity correlates with earlier ipsilateral MD symptom onset.

Methods: We retrospectively reviewed charts of MDhp patients with unilateral or bilateral ES/VA hypoplasia, defined by a vestibular aqueduct angular trajectory (ATVA) >140° in at least one ear on axial CT. VA volumes were semi-automatically segmented from high-resolution temporal bone CT to quantify (mm3) VA hypoplasia.

Results: Of 39 patients, in 34 patients (87%), the smaller VA volume was ipsilateral to the first/only-affected ear (χ²=21.6, p< 0.05). Among 27 (69%) patients with bilateral MD, second-ear symptom onset occurred 6.8 ± 4.7 years after the first (p=0.02). No across-group association was found between inter-ear symptom onset interval and inter-ear VA size difference.

Conclusions: This study reveals two key findings in MDhp: (1) smaller VA volume is consistently associated with the ear affected by MD across the entire cohort; and (2) within individual patients, the smaller VA predicts the first (or only) affected ear. These findings suggest that VA imaging may be a valuable tool for identifying ears at risk for developing MD and understanding disease laterality.