Estimation of the Degree of Endolymphatic Hydrops Using Optical Coherence Tomography

Abstract

Endolymphatic hydrops is a disorder in which an excessive amount of endolymph fluid causes an increase in the pressure of the endolymphatic system of the inner ear. In cochlea, endolymphatic hydrops can cause stretching in the scala media, a tubular construction that, along with two other similar structures, the scala vestibuli and scala tympani, runs through the cochlea from the base to the top. Visualizing the enlargement of the scala media has traditionally been done by histological study of tissue sections, and the degree can be calculated by comparing the ratio of the area of the scala media to the combined total area of the three compartments. However, this requires the obtainment of tissue samples, and thus is not suited for in vivo measurements, and is a labor intensive process in general. Imaging modalities that have been used to measure endolymphatic hydrops include MRI, μMRI and μCT. Recently, optical coherence tomography (OCT) has been applied for visualizing cochlea of mice in vivo. However, just visually discriminating between healthy and afflicted cochlea, and judging the degree of affliction can be difficult. Thus, we aim to establish a new technique for estimating the degree of enlargement of the scala media. We measured two healthy and two diseased cochlea using conventional area calculation, as well as our method, and present results that show that our technique correlates with established standards for measuring the degree of endolymphatic hydrops in cochlea (R=0.977, p=0.5×10⁻⁷).