**Pathophysiology of Meniere's Disease**

Shazia Mirza and Sankalp Gokhale

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/66388

#### **Abstract**

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DOI: 10.1007/s00415‐015‐7930‐1

52 Up to Date on Meniere's Disease

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Meniere's disease, with its characteristic symptom triad of vertigo, balance and hear‐ ing disorders has yet to have its pathophysiology outlined conclusively. Any theory must elucidate all aspects of the natural progression, including vestibular and audi‐ tory symptoms. While the central dogma revolves around endolymphatic hydrops, this theory is not without flaws, such as its inability to explain all the physiological changes seen in patients, or the often absence of symptoms. While several degenera‐ tive changes are observed in temporal bone histopathology, they do not necessarily explain the sequence of events in the development and progress of the disease. This chapter explores the pathophysiology of the disease, focusing on the hydrops theory, while presenting evidence for and against it. Various changes in the inner ear physi‐ ology such as pressure changes, ionic disequilibrium, endocochlear potentials; in human and animal models are described. Alternative explanations for symptoms are discussed. This chapter touches briefly upon etiology associated with Meniere's (and hydrops), and aims to assist a deeper understanding of the relationship of the process to clinical and experimental findings. A clear understanding of the process guides not only the clinical management to improve quality of life but also the direction of future research endeavors.

**Keywords:** Meniere's disease, pathophysiology, etiology, mechanism, endolymphatic hydrops, deafness, vertigo

## **1. Introduction**

Meniere's disease, with a symptom triad of vertigo, balance and hearing disorders, was reported as a disease of the inner ear by Prosper Meniere as far back as 1861 [1] and has yet to have its pathophysiology defined conclusively. Since a central theory of the patho‐ physiology involves endolymphatic hydrops, it is worthwhile be familiar with the terms.

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Endolymph is the potassium‐rich fluid in the membranous labyrinth, produced by the stria vascularis (cells in the scala media) of the cochlear labyrinth along with some contribution from the dark vestibular cells and planum semilunatum. There is a slow longitudinal flow and a fast radial flow of endolymph, also influenced by osmotic and hydrostatic forces. Endolymphatic hydrops refers to the over‐accumulation of endolymph, pressing upon the perilymphatic space resulting in the characteristic symptom triad. The exact mechanism of this hydrops is unknown and can range from over‐production, decreased absorption, to mechanical obstruction. If the cause of the distension or hydrops is unknown, the syndrome can be termed Meniere's disease (MD); conversely, if the cause is known, it is termed second‐ ary endolymphatic blockage. The chapter intends to outline mechanisms for the hydrops; however, this theory is plagued with controversy as shown in a study of cadaveric temporal bone specimens wherein 100% of the diagnosed MD patients had evidence of hydrops, con‐ trasted by findings of hydrops in 51/79 patients without an MD diagnosis, highlighting gaps in this theory [2].
