Differences in Perilymphatic Space Enhancement and Adverse Inflammatory Reaction after Intratympanic Injection of Two Different Gadolinium Agents: A 9.4-Tesla Magnetic Resonance Imaging Study

Publication date: Available online 13 January 2016
Source:Hearing Research
Author(s): Mina Park, Ho Sun Lee, Hyeonjin Kim, Seung Ha Oh, Jun Ho Lee, Myung-Whan Suh
PurposeTo compare the inner ear enhancement after intratympanic injection of two widely used gadolinium (Gd) agents by 9.4 Tesla micro-magnetic resonance imaging (MRI) and to investigate the effects of Gd on the inner ear.MethodsTwelve ears of six rats received intratympanic administration of 1/5 diluted Gd agents: gadoterate meglumine (Gd-DTPA) for the left ear and gadodiamide (Gd-DTPA-BMA) for the right ear. MRI was performed every 30 min from 1 to 4 h after administration. The normalized signal intensity was evaluated by quantitative analysis at each cochlear fluid compartment. Eight, six, and seven ears treated with Gd-DTPA, Gd-DPTA-BMA, and nothing as controls, respectively, were processed for histological evaluation after MRI. After hematoxylin & eosin staining, adverse inflammatory reactions were evaluated for turbid aggregation and lymphocytes.ResultsThe perilymphatic enhancement of Gd-DTPA was superior to that of Gd-DTPA-BMA regardless of cochlear turn, compartment, and time point. Inflammatory reactions were found in 4/8 (50.0%) and 4/6 (66.6%) ears administered Gd-DTPA and Gd-DTPA-BMA, respectively. Regardless of the contrast agent used, inflammatory reactions were most definite in the scala tympani of the basal turn, i.e., near the round window. Slightly greater inflammatory reactions were observed in ears injected with Gd-DTPA-BMA compared to Gd-DTPA although the difference was not statistically significant. No inflammatory reaction was observed in any of the seven controls. The auditory brainstem response threshold was 11.8±2.5 dB SPL before IT Gd injection and it did not change for up to 5 days (15.4±6.6 dB SPL) post-injection.ConclusionsGd-DTPA was superior to Gd-DTPA-BMA for visualization of the inner ear. Administration of diluted Gd agents intratympanically may induce considerable inflammatory reactions in the inner ear.



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