Gadolinium distribution in cochlear perilymph: differences between intratympanic and intravenous gadolinium injection

Three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) imaging 24 h after intratympanic gadolinium injection (IT method) or 4 h after intravenous injection (IV method) has been used to visualize endolymphatic hydrops in Ménière's disease. The aims of this study were to evaluate the difference in gadolinium distribution in cochlear perilymph between the two methods by comparing the enhancement of the basal and apical turns and clarify the pharmacokinetics in cochlear perilymph.

A total of 24 ears of 22 patients who underwent the IT method (gadolinium-diethylene-triamine pentaacetic acid was diluted eightfold with saline) and 28 ears of 17 patients who underwent the IV method (double dose of gadoteridol (0.5 mmol/ml); 0.2 mmol/kg body weight in total amount) at 3 T was analyzed retrospectively. Regions of interest of the perilymph of the cochlear basal turn (B), of the apical turn (A), and the medulla oblongata (M) were determined on each patient. The signal intensity ratios between B and M (BMR), A and M (AMR), and A and B (ABR) were subsequently evaluated.

The IT-BMR (2.63 ± 1.22) was higher than the IV-BMR (1.46 ± 0.45) (p < 0.001). There was no significant difference between the IT- (1.46 ± 0.76) and IV-AMRs (1.21 ± 0.48) (p = 0.15). The IT-ABR (0.58 ± 0.17) was lower than the IV-ABR (0.84 ± 0.22) (p < 0.001).

Gadolinium was predominantly distributed in the basal turn compared with the apical turn in the IT method, whereas it was more uniformly distributed in the IV method. These characteristics might reflect the distribution of therapeutic medications administered either intratympanically or systemically.