Introduction: Canal paresis of the horizontal semicircular canal in Ménière's disease is a frequent finding. Endolymphatic hydrops is the single most characteristic morphologic finding in Ménière's disease. However, the relationship between endolymphatic hydrops and canal paresis is still not elucidated.
Methods: We used magnetic resonance imaging to visualize herniation of parts of the vestibular membranous labyrinth into the horizontal semicircular canal and correlated this morphologic feature with the caloric function of the horizontal semicircular canal.
Results: Patients who showed herniation into the horizontal canal had a significantly impaired caloric function when compared with patients without this morphologic feature.
Conclusion: Herniation into the semicircular canal may be the morphologic correlate for impaired caloric response in patients with Ménière's disease.