Pathophysiology of M??ni??re's Syndrome: Are Symptoms Caused by Endolymphatic Hydrops?

TLDR

Meniere’s syndrome has been linked to endolymphatic hydrops, yet literature reports asymptomatic hydrops and symptomatic cases lacking hydrops, questioning whether hydrops directly causes symptoms. The study aimed to determine whether endolymphatic hydrops is the final common pathway responsible for Meniere’s syndrome symptoms by examining human temporal bones. The authors reviewed 28 temporal bones from clinically diagnosed Meniere’s patients and 79 hydrops cases, and examined a guinea‑pig model where duct obstruction induced spiral‑ligament fibrocyte changes before hydrops. Hydrops was present in all symptomatic cases but also appeared in 19 asymptomatic cases, indicating that hydrops is a histologic marker rather than the direct cause of Meniere’s symptoms.

Abstract

The association of Meniere's syndrome with endolymphatic hydrops has led to the formation of a central hypothesis: many possible etiologic factors lead to hydrops, and hydrops in turn generates the symptoms. However, this hypothesis of hydrops as being the final common pathway has not been proven conclusively.To examine human temporal bones with respect to the role of hydrops in causing symptoms in Meniere's syndrome. If the central hypothesis were true, every case of Meniere's syndrome should have hydrops and every case of hydrops should show the typical symptoms.Review of archival temporal bone cases with a clinical diagnosis of Meniere's syndrome (28 cases) or a histopathologic diagnosis of hydrops (79 cases).All 28 cases with classical symptoms of Meniere's syndrome showed hydrops in at least one ear. However, the reverse was not true. There were 9 cases with idiopathic hydrops and 10 cases with secondary hydrops, but the patients did not exhibit the classic symptoms of Meniere's syndrome. A review of the literature revealed cases with asymptomatic hydrops (similar to the current study), as well as cases where symptoms of Meniere's syndrome existed during life but no hydrops was observed on histology. We also review recent experimental data where obstruction of the endolymphatic duct in guinea pigs resulted in cytochemical abnormalities within fibrocytes of the spiral ligament before development of hydrops. This result is consistent with the hypothesis that hydrops resulted from disordered fluid homeostasis caused by disruption of regulatory elements within the spiral ligament.Endolymphatic hydrops should be considered as a histologic marker for Meniere's syndrome rather than being directly responsible for its symptoms.