Conclusion: The degree of contrast enhancement of the cochlea after intratympanic administration of meglumine gadopentetate (Gd-DTPA) or gadodiamide hydrate (Gd-DTPA-BMA) varies widely among patients with inner ear diseases. There was no morphological change in the stria vascularis after Gd-DTPA or Gd-DTPA-BMA was placed on the round window of guinea pigs. Objectives: We investigated the degree of contrast enhancement of the inner ear after intratympanic administration of ionized and nonionized gadolinium (Gd) contrast agents in patients with inner ear diseases. The inner ear toxicities of these agents were investigated in guinea pigs. Methods: 3D-FLAIR MRI was conducted 1 day after the intratympanic injection of eightfold-diluted Gd-DTPA or Gd-DTPA-BMA in 73 patients with inner ear diseases. Gd enhancement of the basal turn of the cochlea was evaluated as the signal intensity (SI) ratio between the affected and nonaffected sides. In guinea pigs, nondiluted Gd-DTPA, Gd-DTPA-BMA or saline was placed on the round window for 1 h and the stria vascularis was observed using electron microscopy. Results: The SI ratio ranged from 1.5 to 16.5 in the Gd-DTPA group and from 2.5 to 21 in the Gd-DTPA-BMA group. Electron microscopy showed no significant differences in the stria vascularis of guinea pigs in any of the groups.
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