Noninvasive evaluation of endolymphatic space in healthy volunteers using magnetic resonance imaging

Conclusions: A new method for noninvasive standard evaluation of normal endolymphatic space and endolymphatic hydrops using magnetic resonance imaging (MRI) is indicated. Objective: To standardize the evaluation of endolymphatic space in the cochlea and the vestibule in healthy volunteers by applying noninvasive intratympanic gadolinium (Gd) perfusion through the eustachian tube and three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). Methods: This was a prospective study. 3D-FLAIR MRI was performed with a 3 Tesla (3 T) unit 24 h after intratympanic administration of Gd through the eustachian tube in 20 healthy volunteers. Pure tone test and tympanometry were performed 24 h before Gd was administered, and 24 h and 1 month after Gd administration. Results: Gd was present in the perilymph of the inner ear, which clearly displayed the endolymphatic space on 3D-FLAIR MRI with a visible borderline between the perilymph and the endolymph. In healthy volunteers, the normal value for the endolymphatic space in the cochlea ranged between 9% and 28%, and that in the vestibule was between 14% and 40%. No significant changes in pure tone test and tympanometry were noted.