Signal and morphological changes in the endolymph of patients with vestibular schwannoma on non-contrast 3D FLAIR at 3 Tesla.

BACKGROUND: Non-contrast FLAIR revealed increased signal within the inner ear in patients with vestibular schwannoma, which is generally assumed to occur in the perilymph; however, the majority of previous studies did not differentiate between the endolymph and perilymph. Therefore, endolymph signal changes have not yet been investigated in detail. The purpose of the present study was three-fold: (1) to assess perilymph signal changes in patients with vestibular schwannoma on heavily T2-weighted (T2W) 3D FLAIR, also termed positive perilymphatic images (PPI), (2) to evaluate signal and morphological changes in the endolymph on PPI, and (3) to establish whether vertigo correlates with the signal intensity ratios (SIR) of the vestibular perilymph or vestibular endolymphatic hydrops. METHODS: Forty-two patients with unilateral vestibular schwannoma were retrospectively recruited. We semi-quantitatively and qualitatively evaluated the perilymph signal intensity on the affected and unaffected sides. We also quantitatively examined the signal intensity of the vestibular perilymph and assessed the relationship between vertigo and the SIR of the vestibular perilymph on the affected side. We semi-quantitatively or qualitatively evaluated the endolymph, and investigated whether vestibular hydrops correlated with vertigo. RESULTS: The perilymph on the affected side showed abnormal signal more frequently (signal intensity grade: overall mean 1.45 vs. 0.02; comparison of signal intensity: overall mean 36 vs. 0 cases) and in more parts (the entire inner ear vs. the basal turn of the cochlea and vestibule) than that on the unaffected side. No significant difference was observed in the SIR of the vestibular perilymph with and without vertigo (5.54 vs. 5.51, p = 0.18). The endolymph of the vestibule and semicircular canals showed the following characteristic features: no visualization (n = 4), signal change (n = 1), or vestibular hydrops (n = 10). A correlation was not observed between vestibular hydrops and vertigo (p = 1.000). CONCLUSIONS: PPI may provide useful information on signal and morphological changes in the endolymph of patients with vestibular schwannoma. Further research is warranted to clarify the relationship between vertigo and the MR features of the inner ear.

Endolymph magnetic resonance imaging: Contribution of saccule and utricle analysis in the management of patients with sensorineural ear disorders.

Endolymphatic hydrops features excess endolymph in the membranous labyrinth, and is a marker of Menière's disease. Between the early 1980s and late 2000s, MRI in Menière's disease aimed purely to rule out tumor or malformation as differential diagnoses for the pressure disorder. Progress in high-resolution MRI, however, now enables excess endolymph to be visualized in the membranous labyrinth, differentiating saccule and utricle in Menière's disease and in other clinical presentations such as cochleovestibular schwannoma. More recently, non-visibility of the saccule was demonstrated in a subgroup of Menière's disease patients, and utricle atelectasis in case of uni- or bilateral vestibular areflexia. Endolymph quantification remains highly controversial in terms of grading approach, but a simple semiology based on excess or deficient visualization of endolymph according to the compartment sheds light on the pathophysiological mechanisms of cochleovestibular disorder and may in future allow effective monitoring of medical and surgical treatment.

A probabilistic atlas of the human inner ear's bony labyrinth enables reliable atlas-based segmentation of the total fluid space.

Intravenous contrast agent-enhanced magnetic resonance imaging of the endolymphatic space (ELS) of the inner ear permits direct, in-vivo, non-invasive visualization of labyrinthine structures and thus verification of endolymphatic hydrops (ELH). However, current volumetric assessment approaches lack normalization. The aim of this study was to develop a probabilistic atlas of the inner ear's bony labyrinth as a first step towards an automated and reproducible volume-based quantification of the ELS. The study included three different datasets: a source dataset (D1) to build the probabilistic atlas and two testing sets (D2, D3). D1 included 24 right-handed patients (12 females; mean age 51.5 ± 3.9 years) and D2 5 patients (3 female; mean age 48.8 ± 5.01 years) with vestibular migraine without ELH or any measurable vestibular deficits. D3 consisted of five patients (one female; mean age 46 ± 5.2 years) suffering from unilateral Menière's disease and ELH. Data processing comprised three steps: preprocessing using an affine and deformable fusion registration pipeline, computation of an atlas for the left and right inner ear using a label-assisted approach, and validation of the atlas based on localizing and segmenting previously unseen ears. The three-dimensional probabilistic atlas of the inner ear's bony labyrinth consisted of the internal acoustic meatus and inner ears (including cochlea, otoliths, and semicircular canals) for both sides separately. The analyses showed a high level of agreement between the atlas-based segmentation and the manual gold standard with an overlap of 89% for the right ear and 86% for the left ear (measured by dice scores). This probabilistic in vivo atlas of the human inner ear's bony labyrinth and thus of the inner ear's total fluid space for both ears represents a necessary step towards a normalized, easily reproducible and reliable volumetric quantification of the perilymphatic and endolymphatic space in view of MR volumetric assessment of ELH. The proposed atlas lays the groundwork for state-of-the-art approaches (e.g., deep learning) and will be provided to the scientific community.

Magnetic resonance imaging of the endolymphatic space in patients with acute low-tone sensorineural hearing loss.

OBJECTIVE: The aim of this study was to measure the volume of the endolymphatic space (ELS) and to investigate prognosis in patients with acute low-tone sensorineural hearing loss (ALHL). METHODS: A total of 61 ALHL patients participated; 47 were definite while 14 were probable ALHL cases. The definite ALHL patients were classified into three groups: A, "Cure"; B, "No cure"; and C, "Recurrence." Also, nine patients for whom diagnosis changed from ALHL to cochlear Meniere's disease (cMD) without vertigo (ALHL-cMD group). Images of the inner ear fluid space, positive perilymph, and positive endolymph were acquired using a 3T magnetic resonance scanner. Three-dimensional (3D) images were semi-automatically reconstructed using anatomical and tissue information to fuse the 3D images of the inner ear fluid space with the 3D ELS images. RESULTS: Patients in the no cure group showed a significantly higher ELS/total fluid space (TFS) volume ratio in the affected cochlear region than the patients of the other groups. Additionally, the affected vestibular ELS/TFS volume ratio in the cure group was significantly lower than that in the recurrence group. There were significantly higher cochlear and vestibular ELS/TFS ratios in ALHL-cMD patients than in control subjects. CONCLUSIONS: These results indicate that the cochlear ELS/TFS volume ratio should be considered when investigating the extent of recovery, while the extended ELS in the vestibule should be considered when investigating cases of recurrence. Thus, our study suggests that the severe extended ELS appeared likely to change to cMD and that the prognostic determination of ALHL is possible.

[Endolymphatic visualization in patients with Meniere's disease].

OBJECTIVE: To attempt to visualize the endolymph in patients with Meniere's disease by applying non-invasive intratympanic gadolinium through eustachian tube and three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). METHODS: With a 3 Tesla magnetic resonance imaging (MRI) unit, 3D-FLAIR imaging was performed 24 hours after intratympanic gadolinium through eustachian tube in two patients with medically active and intractable Meniere's disease. Pure tone test and tympanometry were performed 24 hours before and after the administration of gadolinium. RESULTS: The gadolinium appeared in almost all parts of the perilymph inside the inner ear; moreover, the border between the perilymph and the endolymph was visible so endolymphatic space was clearly shown on 3D-FLAIR. No change in pure tone test and tympanometry was noted. CONCLUSIONS: 3D-FLAIR MRI with intratympanic gadolinium through eustachian tube can clearly reveal the visualization of endolymph in patients with Meniere's disease. Intratympanic gadolinium therapy through eustachian tube is a safe and effective.

Endolymph movement visualized with light sheet fluorescence microscopy in an acute hydrops model.

There are a variety of techniques available to investigate endolymph dynamics, primarily seeking to understand the cause of endolymphatic hydrops. Here we have taken the novel approach of injecting, via a glass micropipette, fluorescein isothiocyanate-dextran (FITC-dex) and artificial endolymph into scala media of anaesthetized guinea pigs, with subsequent imaging of the inner ear using Light Sheet Fluorescence Microscopy (LSFM) as a means to obtain highly resolved 3D visualization of fluid movements. Our results demonstrate endolymph movement into the utricle, semicircular canals and endolymphatic duct and sac when more than 2.5 µl of fluid had been injected into scala media, with no apparent movement of fluid into the perilymphatic compartments. There was no movement of endolymph into these compartments when less than 2.5 µl was injected. The remarkable uptake of the FITC-dex into the endolymphatic duct, including an absorption into the periductal channels surrounding the endolymphatic duct, highlights the functional role this structure plays in endolymph volume regulation.

Simple Estimation of the Endolymphatic Volume Ratio after Intravenous Administration of a Single-dose of Gadolinium Contrast.

PURPOSE: To evaluate the feasibility of a simple estimation for the endolymphatic volume ratio (endolymph volume/total lymph volume = %ELvolume) from an area ratio obtained from only one slice (%EL1slice) or from three slices (%EL3slices). The %ELvolume, calculated from a time-consuming measurement on all magnetic resonance (MR) slices, was compared to the %EL1slice and the %EL3slices. METHODS: In 40 ears of 20 patients with a clinical suspicion of endolymphatic hydrops, MR imaging was performed 4 hours after intravenous administration of a single dose of gadolinium-based contrast material (IV-SD-GBCM). Using previously reported HYDROPS2-Mi2 MR imaging, the %ELvolume values in the cochlea and the vestibule were measured separately by two observers. The correlations between the %EL1slice or the %EL3slices and the %ELvolume values were evaluated. RESULTS: A strong linear correlation was observed between the %ELvolume and the %EL3slices or the %EL1slice in the cochlea. The Pearson correlation coefficient (r) was 0.968 (3 slices) and 0.965 (1 slice) for observer A, and 0.968 (3 slices) and 0.964 (1 slice) for observer B (P < 0.001, for all). A strong linear correlation was also observed between the %ELvolume and the %EL3slices or the %EL1slice in the vestibule. The Pearson correlation coefficient (r) was 0.980 (3 slices) and 0.953 (1 slice) for observer A, and 0.979 (3 slices) and 0.952 (1 slice) for observer B (P < 0.001, for all). The high intra-class correlation coefficients (0.991-0.997) between the endolymph volume ratios by two observers were observed in both the cochlea and the vestibule for values of the %ELvolume, the %EL3slices and the %EL1slice. CONCLUSION: The %ELvolume might be easily estimated from the %EL3slices or the %EL1slice.

Assessment of Meniere's disease from a radiological aspect - saccular otoconia as a cause of Meniere's disease?

CONCLUSION: Significant reduced visualization of the reuniting duct (ductus reuniens; RD), saccular duct (SD) and endolymphatic sinus (ES) in Meniere's disease (MD) compared with normal control ears on three-dimensional (3D) CT imaging suggests the blockage of endolymphatic flow there with radiodense substances, which may be explained by dislodged otoconia from the saccule. These structures could be involved in the pathogenesis of MD. OBJECTIVE: This study was designed to visualize and assess the RD, SD and ES in patients with MD using 3D CT. METHODS: Sixty-two patients with a definite diagnose of unilateral MD, based on criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), were compared with contralateral ears and normal controls (26 ears) using 3D CT. The RD, SD and ES were scrutinized for patency on 3D CT images. RESULTS: MD ears showed loss of continuity of the RD, SD and ES based on evaluation of 3D CT images, and differed significantly from normal healthy control ears (p < 0.01).