Intratympanic Contrast in the Evaluation of Menière Disease: Understanding the Limits

Abstract

Background and purpose: Studies describing endolymphatic hydrops in Menière disease after off-label intratympanic gadolinium-based contrast have been limited by long acquisition times. We aimed to demonstrate the feasibility of post-intratympanic imaging on a 3T MR imaging system within a clinically tolerable acquisition time and to address potential pitfalls in acquisition or interpretation.

Materials and methods: FDA Investigational New Drug 115,342 and institutional review board approval were obtained for intratympanic injection of 8-fold diluted Gd-DTPA into the more symptomatic ear of 6 adults with Menière disease. 3T MR imaging was performed using a 3-inch surface coil before and up to 28 hours after injection using FLAIR to define the nonenhancing endolymphatic space within the enhancing perilymph. Variable FLAIR TI images were used to determine the impact of fluid-suppression on interpretation. Image quality was assessed for perilymphatic and extralabyrinthine contrast enhancement, definition of endolymphatic anatomy, and other anatomic variants or pathologic findings.

Results: The surface coil afforded 0.375 × 0.375 mm in-plane FLAIR resolution in <4 minutes 30 seconds, sufficient to perceive the nonenhancing spiral lamina, interscalar septa, and endolymphatic structures. Coronal views highlighted a potential interpretation pitfall of vestibular endolymphatic distention overestimation due to partial volume averaging. Varying FLAIR TI resulted in visible changes in the perception of the cochlear endolymphatic space. CSF enhancement was detectable at the internal auditory canal fundus on the injected side in half of the patients, which may confound interpretation.

Conclusions: Using a surface coil preserves high resolution within a clinically acceptable acquisition time. Pitfalls remain regarding the interpretation of these images and optimizing protocols across platforms in the absence of a clear internal reference for standardization.

© 2015 by American Journal of Neuroradiology.

Figures

Fig 1.

Differentiation of the perilymphatic-versus-endolymphatic spaces is evident when comparing FLAIR (A) and FIESTA images (B) obtained 21 hours after IT injection of 1:7 volume/volume diluted Magnevist contrast with a 3-inch surface coil. The nonenhancing fibro-osseous structures are evident on both sequences: the interscalar septa, separating the basal and middle turns and middle and apical turns (arrows), and the spiral lamina apparatus within each cochlear turn (caret). The FLAIR sequence shows central nonenhancement of the endolymphatic space of the vestibule (A, asterisk) and suggestion of distention of the scala media (A, arrowheads) into the scala vestibuli, whereas on FIESTA image (B), the endolymph and perilymph are both hyperintense and indistinguishable (patient 2).

Fig 2.

The nonenhancing endolymphatic space (A, arrow) occupies >33% of the area of the vestibule on axial FLAIR image (A) obtained 28 hours after IT GBCA injection, suggesting endolymphatic distention. Coronal FLAIR obtained concurrently (B) demonstrates that the extent of distention of the endolymphatic space is overestimated on the axial view, due to partial volume averaging and section prescription through the membranous utricle (B, arrow). Partial volume averaging also likely contributes to signal heterogeneity within the semicircular canals (A). Arrowheads (B) correspond to the endolymphatic ductal ampullae of the superior and lateral semicircular canals (patient 6).

Fig 3.

FLAIR imaging performed 28 hours after left IT contrast injection reveals a hyperintense structure (A, arrowhead) extending parallel to the expected course of the vestibular aqueduct (not seen). Comparison with positive-contrast T1-weighted images obtained before IT injection confirms that this structure is an enhancing dural vessel (B and C, arrowheads) coursing parallel to the posterior semicircular canal, extending from the middle cranial fossa to the sigmoid sinus. Correlation with anatomic imaging is imperative to avoid the misinterpretation of dilated endolymphatic space in the vestibular aqueduct (patient 4).

Fig 4.

The impact of variable fluid suppression is visually evident with direct comparison of FLAIR sequences with TIs of 2000 ms (A and D), 2500 ms (B and E), and 2800 ms (C and F), with all other parameters remaining fixed. The nonenhancing scala media (arrowheads) becomes less conspicuous during this short range of TI (A–C), which may result in altered perception of endolymphatic space distention. Variation corresponding to the larger endolymphatic space in the vestibule (arrows, D–F) is less perceptible with changes in TI (patient 4).

Fig 5.

Enhancement is visible at the fundus of the IAC (arrow) on delayed imaging after IT GBCA, conspicuous on FLAIR (A) and T1-weighted imaging (B) in this patient who had profound distention of the endolymphatic space in the basal and middle cochlear turns (arrowheads) (patient 5).