The intravestibular source of the vestibular aqueduct: Its structure and pathology in Ménière's disease

We describe a thin, highly vascular layer of mineralized cartilage, which surrounds most of the endolymphatic duct. In the normal ear this may act in helping to control the chemical composition of endolymph. In Ménière's disease (MD) there is a marked apoptotic change among the mineralized cartilage cells of this layer, which seems to be associated also with the deposition of a pathological substance in the walls of many blood vessels. This may lead to serious chemical change in the nearby endolymph and so provoke the symptoms of MD.

Endolymphatic hydrops is found in all cases of MD, but is not specific for that condition. We sought a cellular change in the vicinity of the saccule that might be more specific than the lesion of endolymphatic hydrops and thus lead to a more successful management of the disease.

We examined stained step sections of 33 autopsy temporal bones from 20 cases of MD, particularly in the region of the vestibule, and compared the changes with those found in a similar region of 65 temporal bones taken from randomly selected cases of non-Ménière conditions.

In all temporal bones there was a well-demarcated region of the posterior vestibule, which formed a skeletal arch around the opening of the tunnel of the vestibular aqueduct into which the endolymphatic duct entered from the vestibule. This 'vestibular arch' was composed mainly of blood vessels and mineralized chondrocytes. The inner skeletal layer surrounding the course of most of the endolymphatic duct in the tunnel of the vestibular aqueduct was composed of the same tissue and was in fact continuous with the vestibular arch. In the non-Ménière temporal bones the mineralized chondrocytes were congregated around normal thin-walled blood vessels and small numbers of them seemed to be undergoing apoptosis in this vicinity. In all of the MD temporal bones, except five in which the vestibular arch was either absent or atrophic, we found pronounced changes of apoptosis among the mineralized cartilage cells and these were associated with proliferative changes in blood vessels in which a bluish-staining translucent deposit, possibly mineralization of the vascular wall, was prominent.