Inner Ear Fluid

Abstract

All sensory hair cells of the inner ear exist in extracellular fluid, but in some areas the fluid has the characteristics of intracellular fluid, as far as concentrations of K⁺ and Na⁺ are concerned. The membranous labyrinth contains the intracellular fluid-like endolymph, and is surrounded by a distinct extracellular fluid, the perilymph. The sensory hair cells of the cochlea are surrounded by extracellular fluid called cortilymph in a separate compartment. Excessive accumulation or leakage of any of these fluids may affect the functions of the whole or partial inner ear.

This chapter is concerned with perilymphatic fistula, signs and symptoms of which mimic Meniere’s disease and sudden deafness. Because the pathophysiology of perilymphatic fistula formation is not clear, we have attempted to experimentally induce leakage of perilymph from the cochlear windows of guinea pigs by injecting artificial perilymph into the subarachnoid space or by suctioning a small amount of perilymph through the round window membrane. In these studies, the membranous labyrinth demonstrated various changes. The cochlea developed endolymphatic hydrops. The vestibular membranous labyrinth collapsed to a greater or lesser degree. In some experimental conditions, the organ of Corti showed cortilymphatic hydrops.