AnalyzeDirect

Endolymphatic hydrops is the pathological hallmark of Menière’s disease, a disorder of the inner ear that causes episodes of vertigo, ringing, a feeling of fullness or pressure in the ear, and fluctuating hearing loss. This particular characteristic of the disease consists of a distension of the endolymphatic space, which is the endolymph-filled area contained by the membranous labyrinth.

Endolymphatic hydrops results in an increased proportion of endolymph within the total fluid space of the inner ear. The endolymph buildup interferes with the normal balance and hearing signals between the inner ear and the brain.

A therapy with proven beneficial effect on the natural course of the disease is still lacking. It is believed though that a future treatment for Menière’s disease should reverse the progression of endolymphatic hydrops, its primary feature. Developing methods that can measure endolymph volume with accuracy is of high importance. This measurement is considered a valuable disease marker, as endolymphatic hydrops progresses with the duration of the syndrome and is linked to the deterioration of audiovestibular functions.

In order to monitor therapeutic trials, scientists from the University of Munich developed a quantitative in vivo approach that aimed to volumetrically quantify endolymph spaces of the inner ear using MR imaging. The protocol used Real-IR sequence to differentiate endolymph from bone and T2-SPACE sequence to delineate total inner ear fluid space from the surrounding bone. These images were re-sampled with cubic interpolation, which was performed for each voxel using continuous and smooth cubic polynomials. Co-registration of the two sets of data was achieved using a normalized entropy measure for multimodality image alignment. Post-processing included separation of the inner ear from the cranial nerves, 3D reconstruction of the inner ear with different color codes for the total fluid space and the endolymphatic space and volume measurements of each region. All of these procedures were performed using Analyze software.

The study demonstrated that the severity of endolymphatic hydrops, which was expressed as the ratio of endolymphatic space to total inner fluid space, strongly correlated with hearing loss. This protocol for MR volumetric assessment is a promising tool that will allow for a quantitative estimation of the effect of therapeutic intervention on Menière’s disease.

Tags: Hearing