Objective: Recently, there have been many reports of intratympanic gentamicin therapy for the treatment of intractable Meniere's disease. Intratympanic administration of steroids has also been used to treat sudden sensorineural hearing loss. We attempted to visualize how the intratympanically administered drug enters the inner ear.
Methods: Gadolinium hydrate diluted eightfold with saline was injected intratympanically through the tympanic membrane using a 23 G needle in nine patients with inner ear diseases. With a 3 Tesla magnetic resonance imaging (MRI) unit, three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) imaging was performed.
Results: 3D-FLAIR MRI clearly revealed that the gadolinium entered the perilymphatic space and delineated the perilymphatic and endolymphatic spaces of the inner ear. In patients with endolymphatic hydrops, the perilymphatic space surrounding the endolymph was small or had disappeared. Gadolinium appeared first in the scala tympani of the basal turn of the cochlea and the perilymphatic space of the vestibule. One day after the intratympanic injection of gadolinium, the gadolinium was observed in almost all parts of the perilymph. Six days after the intratympanic injection, the gadolinium had almost disappeared from the inner ear.
Conclusion: We reported the first visualization of endolymphatic hydrops in patients with Meniere's disease. The relationship between the image of the endolymphatic space and functional tests, such as electrocochleography and vestibular-evoked myogenic potential, must be examined in the near future. It is important for the development of intratympanic drug therapies for inner-ear diseases to investigate how the drugs enter and leave the inner ear.