Effects of gadolinium injected into the middle ear on the stria vascularis

CONCLUSION: The concentration of gadolinium (Gd) used clinically showed no remarkable effects on the stria vascularis; however, a higher concentration had adverse effects. The concentration of Gd must be borne in mind when injecting Gd into the tympanic cavity. OBJECTIVE: Endolymphatic hydrops has been visualized using high resolution MRI with the intratympanic administration of Gd in patients with Meniere's disease. We attempted to investigate the effects of Gd on the stria vascularis. MATERIALS AND METHODS: Gd hydrate diluted eightfold with saline or non-diluted Gd or saline was injected into the tympanic cavity of guinea pigs. To investigate the effects of Gd on the stria vascularis, we measured endocochlear DC potential (EP) and observed the stria vascularis using transmission electron microscopy. RESULTS: Intratympanic injections of Gd hydrate diluted eightfold with saline (1/8 Gd) and saline did not cause apparent changes in the EP. Moreover, the amplitude of the EP decreased significantly 60 min after non-diluted Gd was injected. Transmission electron micrographs of the stria vascularis revealed no significant morphological difference between the ears injected with 1/8 Gd and those injected with saline. There was significant morphological change in the ear injected with non-diluted Gd. The intercellular spaces were markedly enlarged.