The change of hippocampal volume and its relevance with inner ear function in Meniere's disease patients

To reveal the relationship between the disease progression and the hippocampal volume in Meniere's disease, which may indirectly reflect the degree of patients' chronic exposure to stress.

Retrospective review of medical records and brain magnetic resonance image (MRI) of Meniere's disease patients and healthy controls from 2008 to 2013. Age- and sex-matched consecutive 38 definite Meniere's disease patients and 76 healthy controls where brain MRIs, hearing, and vestibular function tests were available. We divided the patients into normal and abnormal groups according to the results functional tests such as pure tone audiometry (PTA), vestibular evoked myogenic potential (VEMP), and bithermal caloric test.

Absolute hippocampal volume of Meniere's disease patients was significantly smaller than that of controls (3.33±0.84cm(3) for left side vs. 3.82±0.37cm(3) for right side, p<0.001). Mean left hippocampal volume of patients with abnormal VEMP and bithermal caloric test on lesion side was significantly smaller than that of the patients with the normal test result (all p<0.05). Average hearing thresholds of the patients showed strong correlation with left hippocampal volumes (p-value<0.001). Those with decreased left hippocampal volume were also more likely to experience augmented emotional stress reactivity.

Meniere's disease patients had significantly decreased hippocampal volume and the volume was significantly correlated with severity of hearing and vestibular function of affected side. This may represent that Meniere's disease patients are exposed to chronic stress for unpredictable vertigo and hearing fluctuation, which finally cause hippocampus atrophy.