In Vivo Visualization of Endolymphatic Hydrops in Guinea Pigs: Magnetic Resonance Imaging Evaluation at 4.7 Tesla

A novel radiomics nomogram based on T2-sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) images for predicting cochlear and vestibular endolymphatic hydrops in Meniere's disease patients

OBJECTIVES

To construct and validate a radiomics nomogram based on T2-sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) images for predicting cochlear and vestibular endolymphatic hydrops (EH) in Meniere's disease patients.

METHODS

A total of 156 patients (312 affected ears) with bilateral definite Meniere's disease who underwent delayed enhancement MRI scans were enrolled in this study. All ears of the patients were divided into a training set (n = 218) and an internal validation set (n = 94). A radiomics nomogram was constructed from radiomics features extracted from the T2-SPACE images, and a radiomics score was calculated. Performance of the radiomics nomogram was assessed using receiver operating characteristics analysis.

RESULTS

Five features were selected for the construction of the cochlear radiomics nomogram, and seven features for the vestibular radiomics nomogram. The radiomics nomograms exhibited robust performance in differentiating between EH-positive and EH-negative statuses in both training and validation cohorts, with the area under the receiver operating characteristics curve values for cochlear and vestibular radiomic nomograms being 0.703 and 0.728 in the training set, and 0.718 and 0.701 in the validation set, respectively.

CONCLUSION

The novel radiomics nomograms based on T2-SPACE images were successfully constructed to predict cochlear and vestibular EH in Meniere's disease. The models showed a solid and superior performance and may play an important role in the EH prediction.

CLINICAL RELEVANCE STATEMENT

We constructed a novel radiomics nomogram, which can be a very useful tool for predicting cochlear and vestibular endolymphatic hydrops in Meniere's disease patients.

KEY POINTS

• This is the first T2-SPACE-based nomogram to predict cochlear and vestibular endolymphatic hydrops. • The nomogram is of great value to patients who are unable to undergo delayed enhancement MRI scans.

Magnetic Resonance Volumetric Quantification of Vestibular Endolymphatic Hydrops in Patients with Unilateral Definite Meniere's Disease Using 3D Inversion Recovery with Real Reconstruction (3D-REAL-IR) Sequence

BACKGROUND

The 3D-REAL-IR MRI sequence allows for an in vivo visualization of endolymphatic hydrops. Qualitative assessment methods of the severity of vestibular and cochlear hydrops are the most commonly used.

METHODS

A quantitative volumetric measurement of vestibular EH in patients with definite unilateral Ménière's disease using the 3D-REAL-IR sequence and the calculation of the endolymphatic ratio (ELR) was intended.

RESULTS

Volumetric calculations of the vestibules, vestibular endolymph and vestibular ELR are performed in 96 patients with unilateral Ménière's disease and correlated with classic qualitative grading scales.

CONCLUSIONS

Quantitative volumetric measurement of vestibular hydrops using the 3D-REAL-IR sequence is feasible and reproducible in daily clinical practice. Vestibular ELR values exceeding 60% defined radiologically significant vestibular hydrops, while values below 30% defined radiologically non-significant vestibular hydrops.

Magnetic Targeting of Gadolinium Contrast to Enhance MRI of the Inner Ear in Endolymphatic Hydrops

OBJECTIVES

1. Determine the feasibility and efficiency of local magnetic targeting delivery of gadolinium (Gad) contrast to the inner ear in rodents. 2. Assess any potential ototoxicity of magnetic targeting delivery of Gad in the inner ear. 3. Study the utility of magnetic targeting delivery of Gad to visualize and quantify endolymphatic hydrops (EH) in a transgenic mouse model.

STUDY DESIGN

Controlled in vivo animal model study.

METHODS

Paramagnetic Gad was locally delivered to the inner ear using the magnetic targeting technique in both rat and mouse models. Efficiency of contrast delivery was assessed using magnetic resonance imaging (MRI). Ototoxicity of Gad was examined with histology of the cochlea and functional audiological tests. The Phex mouse model was used to study EH, hearing loss, and balance dysfunction. Magnetic targeting delivery of Gad contrast was used in the Phex mouse model to visualize the effects of EH using MRI.

RESULTS

Magnetic targeting improved the delivery of Gad to the inner ear and the technique was reproducible in both rat and mouse models. The delivery method did not result in microstructural damage or any significant hearing loss in a normal animal. Magnetic targeting of Gad in the Phex mouse model allowed detailed visualization and quantification of EH.

CONCLUSION

This study provided the first evidence of the effectiveness and efficiency of the local magnetic targeting delivery of gadolinium contrast to the inner ear and its application to the visualization and quantification of EH. Laryngoscope, 133:914-923, 2023.

Dexamethasone does not affect endolymphatic hydrops (EH) in patients with Meniere’s disease within 24 h, and intratympanic administration of gadolinium plus dexamethasone simplifies high-quality imaging of EH using a novel protocol of 7 minutes

Background

Intratympanic administration of gadolinium chelate allows for a better visualization of endolymphatic hydrops (EH) using MRI than intravenous injection and was recently further improved to facilitate high-quality imaging of EH in 7 min. The aim of the present study was to simplify the intratympanic administration protocol by mixing gadolinium chelate with therapeutic dexamethasone and to evaluate the effects of this mixture on the visualization of EH in MRI.

Materials and methods

In an in vitro study, the potential impact of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) on the stability of dexamethasone was evaluated by analyzing dynamic changes in dexamethasone with high-performance liquid chromatography (HPLC) after mixing with Gd-DTPA. Ten patients with definite Meniere's disease (MD) were recruited to study the potential interference of dexamethasone on MRI visualization of EH, and 49 patients with MD were recruited to evaluate the effect of intratympanic injection of Gd-DTPA mixed with dexamethasone on MRI of EH using a 3T MR machine and a novel heavily T2-weighted 3-dimensional fluid-attenuated inversion recovery reconstructed using a magnitude plus zero-filled interpolation (hT₂FLAIR-MZFI) sequence.

Results

The retention times and peak area of dexamethasone in HPLC were not modified by the addition of Gd-DTPA. EH grading in the cochlea and vestibule was not influenced in any ear by intratympanic injection of dexamethasone. Excellent inner ear images were obtained from all patients, and EHs with various grades were displayed. There were significant correlations between diagnosis and cochlear EH (p < 0.01, Spearman's Rho), between diagnosis and vestibular EH (p < 0.01, Spearman's Rho), and between cochlear and vestibular EH (p < 0.01, Spearman's Rho). The distribution of Gd-DTPA plus dexamethasone negatively correlated with the grade of vestibular EH. Injury of the endolymph-perilymph barrier was detected in one cochlea and three vestibules of 59 inner ears with MD.

Conclusions

Intratympanic administration of Gd-DTPA plus dexamethasone yielded high-quality MRI images of EH in patients with MD using a novel 7-min protocol and simplified the clinical application. Intratympanic administration of Gd-DTPA plus dexamethasone might be used to test its therapeutic effect in future work.

Level of evidence

3.

[Clinical and diagnostic criteria and differential diagnosis in the first and second stages of the development of Ménière's disease - A modern view of the problem]

The results of a comprehensive examination of 82 patients with clinical signs of definite Ménière's disease, unilateral lesion and confirmed by extratympanic electrocochleography endolymphatic hydrops are presented. The results of the study showed that only 38% of patients had cochleovestibular syndrome due to Ménière's disease. In 45% of patients, Ménière's disease was combined with other diseases: benign paroxysmal positional vertigo, vestibular migraine, persistent postural-perceptual dizziness, superior semicircular canal dehiscence. In 17% of patients cochleovestibular syndrome was due to other reasons: vestibular migraine, tumor of the posterior cranial fossa, superior canal dehiscence syndrome, Cogan's syndrome, enlarged vestibular aqueduct, otosclerosis. Complaints, medical history of the disease and life, brain MRI, temporal bone CT and pure tone audiometry in dynamics are important in suspected Ménière's disease. For 1 and 2 Ménière's disease stages the most important characteristic are: progressive unilateral sensorineural hearing loss and reduced slow faze velocity values of caloric nystagmus in dynamics, mainly in warm response if attacks of vertigo is maintain; normal head impulse test between vertigo attacks and pathological result of this test in attack of vertigo with the normalization of gain during the first day.

High-quality imaging of endolymphatic hydrops acquired in 7 minutes using sensitive hT2W-3D-FLAIR reconstructed with magnitude and zero-filled interpolation

Background

It is still challenging to detect endolymphatic hydrops (EH) in patients with Meniere’s disease (MD) using MRI. The aim of the present study was to optimize a sensitive technique generating strong contrast enhancement from minimum gadolinium–diethylenetriamine pentaacetic acid (Gd–DTPA) while reliably detecting EH in the inner ear, including the apex.

Materials and methods

All imaging was performed using a 3.0 T MR system 24 h after intratympanic injection of low-dose Gd–DTPA. Heavily T2-weighted 3-dimensional fluid-attenuated inversion recovery reconstructed with magnitude and zero-filled interpolation (hT₂W–FLAIR–ZFI) was optimized and validated in phantom studies and compared with medium inversion time inversion recovery imaging with magnitude reconstruction (MIIRMR). The following parameters were used in hT₂W–FLAIR–ZFI: repetition time 14,000 ms, echo time 663 ms, inversion time 2900 ms, flip angle 120°, echo train length 271, and field of view 166 × 196 mm².

Results

MRI obtained using hT₂W–FLAIR–MZFI yielded high-quality images with sharper and smoother borders between the endolymph and perilymph and a higher signal intensity ratio and more homogenous perilymph enhancement than those generated with MIIRMR (p < 0.01). There were predominantly grade II EHs in the cochleae and grade III EHs in the vestibule in definite MD. EH was detected in the apex of 11/16 ipsilateral ears, 3/16 contralateral ears in unilateral definite MD and 3/6 ears in bilateral MD.

Conclusions

The novel hT₂W–FLAIR–MZFI technique is sensitive and demonstrates strong and homogenous enhancement by minimum Gd–DTPA in the inner ear, including the apex, and yields high-quality images with sharp borders between the endolymph and perilymph.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-06912-4.

MRI With Gadolinium as a Measure of Blood-Labyrinth Barrier Integrity in Patients With Inner Ear Symptoms: A Scoping Review

Objective: Capillaries within the inner ear form a semi-permeable barrier called the blood-labyrinth barrier that is less permeable than capillary barriers elsewhere within the human body. Dysfunction of the blood-labyrinth barrier has been proposed as a mechanism for several audio-vestibular disorders. There has been interest in using magnetic resonance imaging (MRI) with intravenous gadolinium-based contrast agents (GBCA) as a marker for the integrity of the blood labyrinth barrier in research and clinical settings. This scoping review evaluates the evidence for using intravenous gadolinium-enhanced MRI to assess the permeability of the blood-labyrinth barrier in healthy and diseased ears.

Methods: A systematic search was conducted of three databases: PubMed, EMBASE, CINAHL PLUS. Studies were included that used GBCA to study the inner ear and permeability of the blood-labyrinth barrier. Data was collected on MRI protocols used and inner ear enhancement patterns of healthy and diseased ears in both human and animal studies.

Results: The search yielded 14 studies in animals and 53 studies in humans. In healthy animal and human inner ears, contrast-enhanced MRI demonstrated gradual increase in inner ear signal intensity over time that was limited to the perilymph. Signal intensity peaked at 100 min in rodents and 4 h in humans. Compared to controls, patients with idiopathic sudden sensorineural hearing loss and otosclerosis had increased signal intensity both before and shortly after GBCA injection. In patients with Ménière's disease and vestibular schwannoma, studies reported increased signal at 4 h, compared to controls. Quality assessment of included studies determined that all the studies lacked sample size justification and many lacked adequate control groups or blinded assessors of MRI.

Conclusions: The included studies provided convincing evidence that gadolinium crosses the blood-labyrinth barrier in healthy ears and more rapidly in some diseased ears. The timing of increased signal differs by disease. There was a lack of evidence that these findings indicate general permeability of the blood-labyrinth barrier. Future studies with consistent and rigorous methods are needed to investigate the relationship between gadolinium uptake and assessments of inner ear function and to better determine whether signal enhancement indicates permeability for molecules other than gadolinium.

Differential Diagnosis of Endolymphatic Hydrops Between "Probable" and "Definite" Ménière's Disease via Magnetic Resonance Imaging

OBJECTIVES

To investigate the grade of endolymphatic hydrops in patients with "probable" and "definite" Ménière's disease via magnetic resonance imaging (MRI) and to determine whether MRI could assist clinicians in differential diagnosis between probable and definite Ménière's disease.

STUDY DESIGN

Prospective study.

SETTING

Three-dimensional FLAIR MRI (fluid-attenuated inversion recovery) to examine endolymphatic hydrops in Ménière's disease.

METHODS

A total of 51 patients diagnosed with probable (n = 20) or definite (n = 31) unilateral Ménière's disease were enrolled. Three-dimensional FLAIR MRI was performed to evaluate the grade of endolymphatic hydrops. The differences in endolymphatic hydrops between the probable and definite groups were analyzed.

RESULTS

The grade of endolymphatic hydrops was more severe in the definite group than in the probable group (P < .05).

CONCLUSION

MRI revealed a higher grade of endolymphatic hydrops in patients with definite Ménière's disease than in patients with probable Ménière's disease. As a result, it may be clinically useful and an effective tool in the differentiation between definite and probable Ménière's disease.

The Correlation of a 2D Volume-Referencing Endolymphatic-Hydrops Grading System With Extra-Tympanic Electrocochleography in Patients With Definite Ménière's Disease

Background: Although magnetic resonance imaging (MRI) of the membranous labyrinth and electrocochleography (ECochG) have been used to diagnose endolymphatic hydrops (ELH) in patients with Ménière's disease (MD), the relationship between imaging and ECochG is not well-documented. Objectives: This study evaluates the ELH using 3D-FLAIR MRI and extra-tympanic ECochG (ET-ECochG) and correlates the results from 3D-FLAIR MRI to those from ET-ECochG. Materials and Methods: 3D-FLAIR MRI images of 50 patients were assessed using a 2D volume-referencing grading system (VR scores, relative scores according to the known volumes of the cochlea, vestibule, and semicircular canals). Forty healthy subjects were included and compared to 51 definite MD ears of 50 patients while analyzing the ET-ECochG, which used a self-made bronze foil electrode. The amplitude ratio of the summating potential (SP) to the action potential (AP) (SP/AP) and the area ratio of SP to AP (Asp/Aap) were collected. Relative ELH grade scores were then correlated to ET-ECochG (SP/AP, Asp/Aap). Results: The VR scores showed a better correlation (r = 0.88) with the pure tone average (PTA), disease duration, and vertigo frequency of MD than the Bernaerts scores (grading the cochlea and vestibule separately) (r = 0.22). The SP/AP and Asp/Aap of the unilateral MD patients were statistically comparable to those measured in contralateral ears and the results between the definite MD ears with healthy ears were statistically comparable (p < 0.05). In a ROC analysis Asp/Aap (area under curve, AUC 0.98) significantly (p = 0.01) outperformed SP/AP (AUC 0.91). The total score of ELH, vestibular ELH, and cochlear ELH were also correlated with SP/AP and Asp/Aap. The strongest correlation was found between the Asp/Aap and cochlear ELH (r = 0.60). Conclusion: The 2D volume-referencing grading system was more meaningful than the Bernaerts scores. A correlation was found between ELH revealed by 3D-FLAIR MRI and the SP/AP of ET-ECochG in evaluating definite MD patients. The Asp/Aap appeared a more sensitive and reliable parameter than SP/AP for diagnosing the ELH of the membranous labyrinth.

State of the Art Imaging in Menière’s Disease. Tips and Tricks for Protocol and Interpretation

Purpose of Review

Menière’s disease (MD) is a burdensome and not well understood inner ear disorder that has received increasing attention of scientists over the past decade. Until 2007, a certain diagnosis of endolymphatic hydrops (EH) required post-mortem histology. Today, dedicated high-resolution magnetic resonance imaging (MRI) protocols enable detection of disease-related changes in the membranous labyrinth in vivo. In this review, we summarize the current status of MR imaging for MD.

Recent Findings

The mainstays of hydrops imaging are inversion recovery sequences using delayed acquisition after intravenous or intratympanic contrast administration. Based on these techniques, several methods have been developed to detect and classify EH. In addition, novel imaging features of MD, such as blood-labyrinth barrier impairment, have recently been observed.

Summary

Delayed contrast enhanced MRI has emerged as a reliable technique to demonstrate EH in vivo, with promising application in the diagnosis and follow-up of MD patients. Therefore, familiarity with current techniques and diagnostic imaging criteria is increasingly important.

MRI detection of endolymphatic hydrops in Meniere's disease in 8 minutes using MIIRMR and a 20-channel coil after targeted gadolinium delivery

Background

Endolymphatic hydrops (EH) become visible in vertigo patients, particularly in those with Meniere's disease (MD), in vivo using gadolinium-enhanced MRI. However, the image quality is not satisfying after intravenous injection of gadolinium chelate (GdC), and occasional failure in GdC uptake has been noticed after traditional intratympanic injection. In the present report, targeted delivery of GdC and using a cost-effective MRI system to obtain high quality images of EH in only 8 min will be introduced.

Methods

39 MD patients were recruited in the study. First, 0.1 ml of 20-fold diluted gadolinium-diethylenetriamine acid (Gd-DTPA) was delivered onto the posterior upper part of the tympanic medial wall using a soft-tipped micro-irrigation catheter through an artificially perforated tympanic membrane. Inner ear MRI was performed 24 h after Gd-DTPA administration using a 3T MR machine and a 20-channel head/neck coil with an 8 min sequence of medium inversion time inversion recovery imaging with magnitude reconstruction (MIIRMR). The parameters were as follows: TR 16000 ms, TE 663 ms, inversion time 2700 ms, flip angle 180°, slices per slab 60.

Results

Efficient inner ear uptake of Gd-DTPA was detected 24 h after delivery and it created excellent contrast in the inner ear of all cases. High quality images demonstrating EH in the vestibule and cochlea were obtained.

Conclusion

Targeted delivery of minimum Gd-DTPA (0.1 ml, 20-fold dilution) onto the posterior upper portion of the tympanic medial wall and MRI with MIIRMR in a 3T machine and 20-channel head/neck coil are clinically practical to obtain high quality images displaying EH.

Correlations Between the Degree of Endolymphatic Hydrops and Symptoms and Audiological Test Results in Patients With Menière's Disease: A Reevaluation

OBJECTIVE

This study was performed to reevaluate the diagnostic significance of clinically well-accepted audiological tests in indicating endolymphatic hydrops (EH) in Menière's disease (MD).

STUDY DESIGN

Retrospective case review.

SETTINGS

Hospital.

PATIENTS

Fifty patients (52 affected ears) diagnosed with MD were enrolled.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURE

To analyze the correlations between endolymphatic hydrops and results of audiological test including the pure-tone audiometry threshold, suprathreshold function tests, electrocochleogram, and glycerol test.

RESULTS

Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging demonstrated EH in either the vestibule or cochlea to various degrees in all of the MD patients, 24 hours after intratympanic gadolinium chelate injection. Both vestibular and cochlear EH were significantly correlated with PTA threshold. However, EH was not associated with alternate binaural loudness balance or the tone decay test, although a correlation was observed with the short-increment sensitivity index. There was also a correlation between vestibular EH, but not cochlear EH, and the negative summating potential/action potential (-SP/AP) ratio. Neither vestibular EH nor cochlear EH was correlated with the glycerol test results. In addition, the frequency of vertigo attacks, the existence of tinnitus, and aural fullness did not correlate with EH.

CONCLUSIONS

Disrupted ionic homeostasis in the inner ear, but not the EH, may contribute to changes in the -SP/AP ratio. The relevance of glycerol test in identifying EH through detection of hearing changes needs further investigation in the future.

Autoinflammatory characteristics and short-term effects of delivering high-dose steroids to the surface of the intact endolymphatic sac and incus in refractory Ménière's disease

Objective

To investigate immune-related genetic background in intractable Meniere’s disease (MD) and the immediate results of a novel therapy by delivering steroids to the surface of the intact endolymphatic sac (ES) and incus in a sustainable manner.

Case report and methods

Candidate genes involved in immune regulation were sequenced using a next-generation sequencing method in a patient with intractable MD. Mutations were confirmed using the Sanger sequencing method. The ES was exposed, and gelatin sponge particles were immersed in high-dose methylprednisolone solution and placed onto the surface of ES. “L”-shaped gelatin sponge strips were immersed in dexamethasone solution and served as a guiding device for the steroids by touching the incus and gelatin sponge particles on the surface of the ES. Gelatin sponge particles immersed in dexamethasone solution were placed around the gelatin sponge strips and sealed using fibrin glue.

Results

Autoinflammation in the refractory MD case was indicated by genotype, including novel heterozygous mutations of PRF1, UNC13D, SLC29A3, ITCH, and JAK3, as well as phenotype. The vertigo was fully relieved immediately after operation. Tinnitus and aural fullness were resolved 3 weeks after operation, whereas hearing improved in 2 mon postoperation. No recurrence was noted during the 5-monfollow-up, and the final MRI supported the novel therapeutic hypothesis.

Conclusion

Autoinflammation was involved in a refractory MD. This novel therapy, which involves the delivery of steroids to the surface of the intact ES and incus, is effective in relieving vertigo and tinnitus and improves hearing function of refractory MD.

Imaging of Ménière Disease

Visualization of the morphologic substrate of Ménière disease, the endolymphatic hydrops, can be performed using noncontrast or contrast-enhanced MR imaging techniques. Noncontrast MR imaging uses a heavily T2-weighted sequence; however, its reproducibility remains to be confirmed. Contrast-enhanced MR imaging techniques mainly use a 3-dimensional fluid-attenuated inversion recovery sequence after intratympanic gadolinium administration or after a 4-hour delayed intravenous gadolinium administration. The latter technique is most frequently used and is able to detect and grade Ménière disease. It is a reliable technique with a high diagnostic accuracy, enabling visualization of endolymphatic hydrops.

Gentamicin delivery to the inner ear: Does endolymphatic hydrops matter?

Introduction

Middle ear application of gentamicin is a common medical treatment for uncontrolled Ménière’s disease. The objective of the study was to evaluate the impact of endolymphatic hydrops on inner ear delivery.

Methods

Perilymph gentamicin concentrations and correlation with endolymphatic hydrops in an animal model were assessed. A group of 24 guinea pigs was submitted to surgical obstruction of the endolymphatic sac and duct of the right ear. Gentamicin was applied either to the right ear’s round window niche or through a transtympanic injection. Perilymph specimens were collected at different times. Histologic morphometry was used to evaluate both turn-specific and overall hydrops degree.

Results

In animals with endolymphatic hydrops, lower concentrations of gentamicin were observed after 20 or 120 minutes of exposure and in both types of administration, when compared to controls. This difference reached statistical significance in the round window niche application group (Mann-Whitney, p = 0,007). A negative correlation between perilymphatic gentamicin concentration and hydrops degree could be observed in both groups, after 120 minutes of exposure (Spearman correlation, round window niche p<0,001; TT p = 0,005).

Conclusions

The study indicates that the endolymphatic hydrops degree has a negative interference on the delivery of gentamicin into the inner ear following middle ear application.

Small animal, positron emission tomography-magnetic resonance imaging system based on a clinical magnetic resonance imaging scanner: evaluation of basic imaging performance

Development of advanced preclinical imaging techniques has had an important impact on the field of biomedical research, with positron emission tomography (PET) imaging the most mature of these efforts. Developers of preclinical PET scanners have joined the recent multimodality imaging trend by combining PET imaging with other modalities, such as magnetic resonance imaging (MRI). Our group has developed a combined PET-MRI insert for the imaging of animals up to the size of rats in a clinical 3T MRI scanner. The system utilizes a sequential scanner configuration instead of the more common coplanar geometry. The PET component of the system consists of a ring of 12 liquid-cooled, SiPM-based detector modules ( diameter = 15.2    cm ). System performance was evaluated with the NEMA NU 4-2008 protocol. Spatial resolution is ∼ 1.71    mm 5 cm from the center of the field-of-view measured from single-slice rebinned filtered backprojection-reconstructed images. Peak noise equivalent count rate is 17.7 kcps at 8.5 MBq; peak sensitivity is 2.9%. The MRI component of the system is composed of a 12-cm-diameter birdcage transmit/receive coil with a dual-preamplifier interface possessing very low noise preamplifiers. System performance was evaluated using American College of Radiology-based methods. Image homogeneity is 99%; the ghosting ratio is 0.0054. The signal-to-noise ratio is 95 and spatial resolution is ∼ 0.25    mm . There was no discernable cross-modality interference.

Menière and Friends: Imaging and Classification of Hydropic Ear Disease

BACKGROUND

Over 75 years ago, endolymphatic hydrops was discovered as the pathologic correlate of Menière's disease. However, this pathologic finding could be ascertained only in postmortem histologic studies. Due to this diagnostic dilemma and the variable manifestation of the various audiovestibular symptoms, diagnostic classification systems based on clinical findings have been used hitherto.

METHODS

A review of the literature of magnetic resonance (MR) imaging of hydropic ear disease.

RESULTS

Recent developments of high resolution MR imaging of the inner ear have now enabled us to visualize in vivo endolymphatic hydrops in patients with suspected Menière's disease. The existing knowledge from temporal bone histologic studies and from the emerging evidence on imaging based evaluation of patients with suspected Menière's disease indicate that endolymphatic hydrops not only is responsible for the full-blown clinical triad of simultaneous attacks of auditory and vestibular dysfunction, but also for other clinical presentations such as "vestibular" and "cochlear Menière's disease."

CONCLUSION

As a consequence, we propose the term "Hydropic Ear Disease" as a new terminology which is based on symptomatic and imaging characteristics of these clinical entities to clarify and simplify their diagnostic classification.

[Trial of Micro CT Scanner SKYSCAN1176 for the Imaging of the Guinea Pig Cochlea in vivo]

The usefulness of the micro CT scanner system SKYSCAN1176 was evaluated for the study of the guinea pig cochlea. Each slice of the section was 9 μm and we were able to identify each ossicles, modiolus, upper, middle, and basal turn of the cochlea. This scanner enables us to observe inner ear structure repeatedly in vivo.

Meniere's disease

Meniere's disease (MD) is a disorder of the inner ear that causes vertigo attacks, fluctuating hearing loss, tinnitus and aural fullness. The aetiology of MD is multifactorial. A characteristic sign of MD is endolymphatic hydrops (EH), a disorder in which excessive endolymph accumulates in the inner ear and causes damage to the ganglion cells. In most patients, the clinical symptoms of MD present after considerable accumulation of endolymph has occurred. However, some patients develop symptoms in the early stages of EH. The reason for the variability in the symptomatology is unknown and the relationship between EH and the clinical symptoms of MD requires further study. The diagnosis of MD is based on clinical symptoms but can be complemented with functional inner ear tests, including audiometry, vestibular-evoked myogenic potential testing, caloric testing, electrocochleography or head impulse tests. MRI has been optimized to directly visualize EH in the cochlea, vestibule and semicircular canals, and its use is shifting from the research setting to the clinic. The management of MD is mainly aimed at the relief of acute attacks of vertigo and the prevention of recurrent attacks. Therapeutic options are based on empirical evidence and include the management of risk factors and a conservative approach as the first line of treatment. When medical treatment is unable to suppress vertigo attacks, intratympanic gentamicin therapy or endolymphatic sac decompression surgery is usually considered. This Primer covers the pathophysiology, symptomatology, diagnosis, management, quality of life and prevention of MD.

What is Menière's disease? A contemporary re-evaluation of endolymphatic hydrops

Menière's disease is a chronic condition with a prevalence of 200-500 per 100,000 and characterized by episodic attacks of vertigo, fluctuating hearing loss, tinnitus, aural pressure and a progressive loss of audiovestibular functions. Over 150 years ago, Prosper Menière was the first to recognize the inner ear as the site of lesion for this clinical syndrome. Over 75 years ago, endolymphatic hydrops was discovered as the pathologic correlate of Menière's disease. However, this pathologic finding could be ascertained only in post-mortem histologic studies. Due to this diagnostic dilemma and the variable manifestation of the various audiovestibular symptoms, diagnostic classification systems based on clinical findings have been repeatedly modified and have not been uniformly used in scientific publications on Menière's disease. Furthermore, the higher level measures of impact on quality of life such as vitality and social participation have been neglected hitherto. Recent developments of high-resolution MR imaging of the inner ear have now enabled us to visualize in vivo endolymphatic hydrops in patients with suspected Menière's disease. In this review, we summarize the existing knowledge from temporal bone histologic studies and from the emerging evidence on imaging-based evaluation of patients with suspected Menière's disease. These indicate that endolymphatic hydrops is responsible not only for the full-blown clinical triad of simultaneous attacks of auditory and vestibular dysfunction, but also for other clinical presentations such as "vestibular" and "cochlear Menière's disease". As a consequence, we propose a new terminology which is based on symptomatic and imaging characteristics of these clinical entities to clarify and simplify their diagnostic classification.

An Overview of Nanoparticle Based Delivery for Treatment of Inner Ear Disorders

Nanoparticles offer new possibilities for inner ear treatment as they can carry a variety of drugs, protein, and nucleic acids to inner ear. Nanoparticles are equipped with several functions such as targetability, immuno-transparency, biochemical stability, and ability to be visualized in vivo and in vitro. A group of novel peptides can be attached to the surface of nanoparticles that will enhance the cell entry, endosomal escape, and nuclear targeting. Eight different types of nanoparticles with different payload carrying strategies are available now. The transtympanic delivery of nanoparticles indicates that, depending on the type of nanoparticle, different migration pathways into the inner ear can be employed, and that optimal carriers can be designed according to the intended cargo. The use of nanoparticles as drug/gene carriers is especially attractive in conjunction with cochlear implantation or even as an inclusion in the implant as a drug/gene reservoir.

Vasopressin induces endolymphatic hydrops in mouse inner ear, as evaluated with repeated 9.4 T MRI

From histopathological specimens, endolymphatic hydrops has been demonstrated in association with inner ear disorders. Recent studies have observed findings suggestive of hydrops using MRI in humans. Previous studies suggest that vasopressin may play a critical role in endolymph homeostasis and may be involved in the development of Ménière's disease. In this study we evaluate the effect of vasopressin administration in vivo in longitudinal studies using two mouse strains. High resolution MRI at 9.4 T in combination with intraperitoneally delivered Gadolinium contrast, was performed before and after chronic subcutaneous administration of vasopressin via mini-osmotic pumps in the same mouse. A development of endolymphatic hydrops over time could be demonstrated in C57BL6 mice (5 mice, 2 and 4 weeks of administration) as well as in CBA/J mice (4 mice, 2 weeks of administration; 6 mice, 3 and 4 weeks of administration). In most C57BL6 mice hydrops developed first after more than 2 weeks while CBA/J mice had an earlier response. These results may suggest an in vivo model for studying endolymphatic hydrops and corroborates the future use of MRI as a tool in the diagnosis and treatment of inner ear diseases, such as Ménière's disease. MRI may also be developed as a critical tool in evaluating inner ear homeostasis in genetically modified mice, to augment the understanding of human disease.

The predominant vestibular uptake of gadolinium through the oval window pathway is compromised by endolymphatic hydrops in Ménière's disease

OBJECTIVE

Intratympanic administration of gentamicin is becoming a common therapy to control vertigo in Ménière's disease (MD). Drug entry through an oval window pathway was recently demonstrated in rats. The present study aimed to evaluate the permeability of the oval window to gadolinium in MD patients.

METHODS

Eight patients with MD and other inner ear diseases received a transtympanic injection of 5-fold diluted gadopentetate dimeglumine (Gd-DTPA). Three-dimensional fluid-attenuated inversion-recovery (3D-FLAIR) and 3D inversion recovery turbo spin echo with real reconstruction (3D-real IR) imaging was performed using a 3-Tesla MRI scanner at 3, 6, 12, and 24 h after injection. The extent of vestibular endolymphatic hydrops (EH) was determined, and the dynamics of the signal changes in the vestibule and the cochlear basal turn were evaluated.

RESULTS

Transtympanically injected Gd-DTPA entered the cochlea of all 8 of the patients and entered the vestibule of 7 of the 8 patients. EH was demonstrated in 2 patients with MD and the patient with idiopathic sensorineural hearing loss or idiopathic vertigo. In the patients lacking EH, the vestibules exhibited more efficient uptake of Gd-DTPA than did the cochleae. In the patients with vestibular EH, the Gd-DTPA signal in the vestibule was less intense than that in the cochlear basal turn.

CONCLUSION

In patients with inner ear diseases, the vestibular distribution of Gd-DTPA was compromised by vestibular EH, suggesting oval window passage of Gd-DTPA is reduced in the presence of EH.

Markers of cochlear inflammation using MRI

PURPOSE

To quantify spatial and temporal inflammation-induced changes in vascular permeability and macrophage infiltration in guinea-pig (GP) cochlea using MRI.

MATERIALS AND METHODS

GPs were injected with lipopolysaccharide (LPS) to induce cochlear inflammation. One group was injected with a gadolinium based contrast agent (GBCA) and dynamic contrast enhanced (DCE)-MRI was performed at 4, 7, and 10 days after LPS treatment. A two-compartment pharmacokinetic model was used to determine the apparent rate constant of GBCA extravasation (K(trans) ). A second group was injected with ultrasmall superparamagnetic iron oxide particles (USPIOs) and studied at 2, 3, and 7 days after LPS treatment to detect tissue USPIO uptake and correlate with histology. For both groups, control GPs were scanned similarly.

RESULTS

The signal enhancement increased substantially and more rapidly at day 4 in LPS-treated than in control cochlea shortly following GBCA injection. K(trans) of LPS-treated cochlea was maximum on day 4 at 0.0218 ± 0.0032 min(-1) and then decreased to control level at 0.0036 ± 0.0004 min(-1) by day 10. In the second group, the relative signal intensity and T2 in cochlear perilymphatic spaces on day 2 decreased, on average, by 54% and 45%, respectively, compared with baseline and then remained under control levels by day 7. This suggests the infiltration of inflammatory cells, although unconfirmed by histology.

CONCLUSION

This provides the first measurement of cochlear vascular permeability using MRI and a quantitative evaluation of the development of cochlear inflammation. MRI holds considerable potential for the assessment of disease processes such as clinical diagnosis of conditions such as labyrinthitis.

Meniere's disease: a reappraisal supported by a variable latency of symptoms and the MRI visualisation of endolymphatic hydrops

OBJECTIVES

To evaluate the onset of vertigo, hearing loss and tinnitus in Ménière's disease and the associated endolymphatic hydrops (EH) of the inner ear.

DESIGN

Multicentre evaluation of three patient groups.

SETTINGS

Disease-specific symptoms were reviewed among referred patients in a tertiary referral hospital in Finland and in members of a Finnish Ménière Association in Finland. The MRI of a separate group of patients was undertaken in a tertiary referral centre in Japan.

PARTICIPANTS

340 patients were reviewed in the referral hospital along with 740 members of the Ménière Association. MRI was undertaken in 224 patients in Japan.

PRIMARY AND SECONDARY OUTCOME MEASURES

Latency and symptom development in Ménière's disease, and the appearance of EH of the inner ear in monosymptomatic patients and in Ménière's disease.

RESULTS

The mean age of the first symptom was 43.8 years, with 10% of the patients being older than 65 years. The time delay between hearing loss and vertigo was more than 5 years in 20% of the members and of the patients. Gadolinium-contrasted MRI demonstrated EH in 90% of the patients with Ménière's disease, in which 75% was bilateral among patients with unilateral symptoms. In monosymptomatic patients with vertigo, tinnitus or hearing loss; EH was demonstrated in 55-90% of the patients either in the cochlea and/or the vestibulum of the symptomatic ear.

CONCLUSIONS

Ménière's disease often shows bilateral EH and comprises a continuum from a monosymptomatic disease to the typical symptom complex of the disease. We suggest that a 3T MRI measurement should be carried out in patients with sensory-neural hearing loss, vertigo and tinnitus, 4 h after the intravenous injection of a gadolinium-contrast agent to verify the inner ear pathology. This may lead to a better management of the condition.

Endolymphatic hydrops in Meniere's disease detected by MRI after intratympanic administration of gadolinium: comparison with sudden deafness

CONCLUSION

The detection rate of endolymphatic hydrops was significantly higher in patients with Meniere's disease compared with those with sudden deafness, indicating that 3 T magnetic resonance imaging (MRI) with intratympanic gadolinium injection was effective in diagnosing endolymphatic hydrops.

OBJECTIVES

To compare the detection rate of endolymphatic hydrops between patients with Meniere's disease and sudden deafness as controls by 3 T MRI after intratympanic gadolinium injection with conventional pulse sequence such as two-dimensional fluid-attenuated inversion recovery.

METHODS

Ten patients with unilateral Meniere's disease and eight with sudden deafness underwent inner ear MRI 24 h after intratympanic gadolinium injection.

RESULTS

The endolymphatic space was detected as a low signal intensity area, while the perilymphatic space showed high intensity by gadolinium enhancement. Due to faint enhancement, images could not be evaluated in 1 of 10 patients with Meniere's disease. However, the other nine patients together with two of the eight with sudden deafness were diagnosed as having hydrops. The difference in detection rates between the two diseases was statistically significant. Two hydrops-positive cases with sudden deafness were considered to be of the secondary type of hydrops, because images were taken after partial recovery from hearing loss several months after the onset of the disease.

Transport augmentation through the blood-inner ear barriers of guinea pigs treated with 3-nitropropionic acid and patients with acute hearing loss, visualized with 3.0 T MRI

OBJECTIVE

To visualize the permeability changes in the blood-inner ear barriers of guinea pigs with acute mitochondria dysfunction and in patients with acute hearing loss using contrast agent-enhanced MRI.

MATERIALS AND METHODS

An animal model of acute mitochondria dysfunction-induced hearing loss was created by introducing 3-nitropropionic acid (3-NP) intratympanically in guinea pigs. Vestibular disorder and hearing loss were evaluated. An MRI was performed at 2 h after either intravenous (IV) or intratympanic administration of dimeglumine gadopentetate (Gd-DTPA), using 3D fast-recovery fast spin-echo (FRFSE) and 3D fluid-attenuated inversion recovery (FLAIR) sequences. The inner ears of patients with acute hearing loss were imaged using a 3D-FLAIR sequence with a 3 T MRI machine at 2 h post-IV injection with Gd-DTPA at a routine dosage.

RESULTS

Guinea pigs treated with 3-NP showed severe hearing loss and vestibular dysfunction. MR imaging with a 3D-FLAIR sequence at 2 h post-IV injection of Gd-DTPA was an optimal method for visualizing transport augmentation through the blood-inner ear barriers. Apoptosis appeared in the stria vascularis and Reissner's membrane of cochleae treated with 3NP. Similar MRI changes were observed in patients with SSHL and Ménière's disease 2 h post-IV injection with Gd-DTPA using the 3D-FLAIR sequence.

CONCLUSION

Variations of Gd-DTPA transport through the blood-inner ear barriers induced by mitochondria toxin was visualized in guinea pigs using a clinical 3.0 T machine. IV injection of Gd-DTPA with 2 h of waiting time and imaging with 3D-FLAIR are optimal methods. The MRI observation of the inner ear in the animal model was translatable to patients with acute hearing loss, using an IV injection of Gd-DTPA at the routine dosage.

Magnetic resonance imaging of the inner ear in Meniere's disease

Recent magnetic resonance imaging (MRI) techniques have made it possible to examine the compartments of the cochlea using gadolidium-chelate (GdC) as a contrast agent. As GdC loads into the perilymph space without entering the endolymph in healthy inner ears, the technique provides possibilities to visualize the different cochlear compartments and evaluate the integrity of the inner ear barriers. This critical review presents the recent advancements in the inner ear MRI technology, contrast agent application and the correlated ototoxicity study, and the uptake dynamics of GdC in the inner ear. GdC causes inflammation of the mucosa of the middle ear, but there are no reports or evidence of toxicity-related changes in vivo either in animals or in humans. Intravenously administered GdC reached the guinea pig cochlea about 10 minutes after administration and loaded the scala tympani and scala vestibuli with the peak at 60 minutes. However, the perilymphatic loading peak was 80 to 100 minutes in mice after intravenous administration of GdC. In healthy animals the scala media did not load GdC. In mice in which GdC was administered topically onto the round window, loading of the cochlea peaked at 4 hours, at which time it reached the apex. The initial portions of the organ to be filled were the basal turn of the cochlea and vestibule. In animal models with endolymphatic hydrops (EH), bulging of the Reissner's membrane was observed as deficit of GdC in the scala vestibuli. Histologically the degree of bulging correlated with the MR images. In animals with immune reaction-induced EH, MRI showed that EH could be limited to restricted regions of the inner ear, and in the same inner ear both EH and leakage of GdC into the scala media were visualized. More than 100 inner ear MRI scans have been performed to date in humans. Loading of GdC followed the pattern seen in animals, but the time frame was different. In intravenous delivery of double-dose GdC, the inner ear compartments were visualized after 4 hours. The uptake pattern of GdC in the perilymph of humans between 2 hours and 7 hours after local delivery needs to be clarified. In almost all patients with probable or suspected Ménière's disease, EH was verified. Specific algorithms with a 12-pole coil using fluid attenuation inversion recovery sequences are recommended for initial imaging in humans.

MRI manifestation of novel superparamagnetic iron oxide nanoparticles in the rat inner ear

AIM

Superparamagnetic iron oxide nanoparticles hierarchically coated with oleic acid and Pluronic F127 copolymers (POA@SPION) have shown exceptional T2 contrast enhancement. The aim of the present work was to investigate the MRI manifestation of POA@SPION in the inner ear.

MATERIALS & METHODS

A total of 26 male Wister rats were selected for testing POA@SPION administered through intracochlear, intratympanic and intravenous routes. MRI was performed with a 4.7 T MR scanner.

RESULTS & CONCLUSION

POA@SPION can be introduced into the perilymph space, after which it becomes widely distributed and can demonstrate the integrity of the perilymph-endolymph barrier. Positive highlighting of the endolymph compartment against the darkened perilymph was visualized for the first time. POA@SPION passed through the middle-inner ear barriers in only small amounts, but stayed in the perilymph for 3 days. They did not traverse the blood-perilymph barrier or blood-endolymph barrier. The inner ear distribution of POA@SPION was confirmed by histology. POA@SPION is a promising T2 negative contrast agent.

Magnetic resonance imaging of guinea pig cochlea after vasopressin-induced or surgically induced endolymphatic hydrops

Objective: To investigate the ability to detect the in vivo cochlear changes associated with vasopressin-induced and surgically induced endolymphatic hydrops using MRI at 3 tesla (T).

Study Design: Prospective, animal model.

Setting: Animal laboratory.

Subjects and Methods: In group 1, five guinea pigs underwent post–gadolinium temporal bone MRI before and after seven and 14 days of chronic systemic administration of vasopressin by osmotic pump. In group 2, five guinea pigs underwent temporal bone MRI eight weeks after unilateral surgical ablation of the endolymphatic sac. Three-tesla high-resolution T1-weighted sequences were acquired pre- and postcontrast administration. Region of interest signal intensities of the perilymph and endolymph were analyzed manually. Quantitative evaluation of hydrops was measured histologically.

Results: Gadolinium preferentially concentrated in the perilymph, allowing for distinction of cochlear compartments on 3.0-T MRI. The T1-weighted contrast MRI of vasopressin-induced hydropic cochlea showed significant increases in signal intensity of the endolymph and perilymph. Surgically induced unilateral hydropic cochlea also showed increased signal intensity, compared with the control cochlea of the same animal, but less of an increase than the vasopressin group. The histological degree of hydrops induced in the vasopressin group was comparable to previous studies.

Conclusions: In vivo postcontrast MRI of the inner ear demonstrated cochlear changes associated with chronic systemic administration of vasopressin and surgical ablation of the endolymphatic sac. Understanding the MRI appearance of endolymphatic hydrops induced by various methods contributes to the future use of MRI as a possible tool in the diagnosis and treatment of Ménière's disease.

Differential passage of gadolinium through the mouse inner ear barriers evaluated with 4.7T MRI

Magnetic resonance imaging (MRI), supplemented by contrast agents, is a powerful tool that can be used to visualise the structures of the inner ear in vivo and assess some aspects of physiology, such as the permeability of agents through membranes. The mouse is an excellent animal species for investigating human diseases, including hearing loss but detailed MRI studies with contrast have not been reported. In this work, we aimed to demonstrate the limits of MR imaging resolution of the fine inner ear structures in the mouse and to explore the permeability of the intracochlear barriers to gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) administered by intravenous injection (IV) or intratympanic (IT) routes. Twenty-three female FVB mice were imaged with a 4.7-T MR scanner using both 2D and high resolution 3D sequences. Inner ear region of interest (ROI) signal intensities and perilymph volumes were evaluated. Finer structures were studied using 3D acquisition and reconstruction techniques and comparisons were made to similarly oriented histological sections that were examined by light microscopy. Gd-DOTA enhancement occurred in the perilymphatic compartment and highlighted the contiguous inner ear structures, but enhancement did not appear within the endolymph. The dynamic uptake of Gd-DOTA in the perilymphatic compartments reached an initial plateau 80min after IV administration and continued to slightly increase to a maximum level by 100min. The perilymph volume demonstrated by Gd-DOTA uptake was statistically significantly larger in the IV group (1.72mm(3)) than in the IT group (1.28mm(3)) (p<0.05).

Visualization of inner ear disorders with MRI in vivo: from animal models to human application

CONCLUSION

The inner ear membranous permeability and leakiness and endolymphatic hydrops can be visualized using gadolinium-enhanced MRI in both rodents and man. Intratympanic administration of contrast agent gives greater perilymphatic loading of gadolinium.

OBJECTIVES

Visualization of different types of inner ear dysfunction in MRI with intravenous or intratympanic administration of contrast agent.

MATERIALS AND METHODS

In the animal study, gadolinium was administered intravenously or intratympanically and imaged with 4.7 T MRI. In man, gadolinium was delivered intratympanically and studied with 1.5 T or 3 T MRI.

RESULTS

In the animals, intravenous delivery of gadolinium demonstrated uptake in the perilymph of normal inner ears. The cochlear modiolus appeared to be a critical site for the secretion of perilymph and the location of fluid communication between the perilymphatic scalae. Intense noise exposure and immune reaction caused cochlear injury and accelerated gadolinium passage through the blood-perilymph and blood-endolymph barriers. In man, perilymphatic uptake of gadolinium was only observed in the impaired inner ear when administered intravenously. However, the signal-to-noise ratio of images was improved when gadolinium was delivered intratympanically. MRI demonstrated endolymphatic hydrops in both animal models and patients with Meniere's disease.

Ménière disease: diagnostic instrumental support

The current guidelines of the American Academy of Otolaryngology-Head and Neck Surgery entrust the diagnosis of Ménière disease (MD) only to the clinical presentation and the pure tone audiometry. However, most otolaryngologists request a widened instrumental evaluation of the patients suspected of MD. The effective reliability of the further instrumental support for the diagnosis of MD is still debated in the literature because of nonstandardized procedures and sometimes incoherence among authors. New and more sophisticated diagnostic tests have been developed both in audiovestibology and in imaging in the last few years. A review of the recent literature on this controversial subject is provided.

3 Tesla delayed contrast magnetic resonance imaging evaluation of Ménière's disease

OBJECTIVE

To determine whether 3 Tesla (T) magnetic resonance imaging (MRI) with delayed contrast imaging has sufficient anatomic resolution to image the intracochlear fluid spaces (i.e., the scala tympani, scala media, and scala vestibuli) of the inner ear and identify endolymphatic hydrops in vivo.

STUDY DESIGN

Four normal subjects underwent 3T MRI scanning after the administration of gadodiamide intravenous (IV) contrast. MRI region of interest signal intensity was used to determine the diffusion of gadodiamide into the perilymphatic fluid spaces over time. Seven subjects with unilateral Ménière's disease underwent 3T MRI 4 hours after administration of gadodiamide IV contrast agent.

RESULTS

All four normal subjects demonstrated perilymphatic enhancement by 4 hours postinjection. Loss of definition of the membranous cochlea was noted in five of the seven subjects with Ménière's disease. Precise definition of the scala media could not be achieved with this imaging protocol.

CONCLUSION

Delayed contrast imaging of the inner ear with 3T MRI revealed in vivo changes of the membranous labyrinth consistent with unilateral Ménière's disease.

Evaluation of low-frequency biasing as a diagnostic tool in Menière patients

Although it is generally accepted that endolymphatic hydrops is the cause of complaints in patients suffering from Menière's disease, it has not been possible up to now to prove the presence of an endolymphatic hydrops in living humans. This study evaluated the psychophysical method introduced by Mrowinski et al. [Mrowinski D., Gerull G., Nubel K., Scholz G., 1995. Masking and pitch shift of tone bursts and clicks by low-frequency tones. Hear. Res. 85, 95-102; Mrowinski D., Scholz G., Krompass S., Nubel K., 1996. Diagnosis of endolymphatic hydrops by low-frequency masking. Audiol. Neurootol. 1, 125-134] to diagnose endolymphatic hydrops. These authors used low frequency biasing to differentiate between individuals with and individuals without Menière's disease. In the present study no statistically significant differences in masking parameters could be found between a large number (n=91) of ears with Menière's disease and ears (n=52) with comparable sensorineural hearing losses, but without symptoms of Menière's disease. Our results support the idea that results deviating from normal in low frequency biasing measurements are not due to endolymphatic hydrops itself, but to other pathological changes of the inner ear. An explanation could be that with increasing hearing loss the gain of the cochlear amplifier decreases, leading to smaller modulation depths.

Endoscopically guided placement of prefabricated cochlear implant electrodes in a common cavity malformation

OBJECTIVE

To devise a safe and effective method of optimal customized electrode placement in the common cavity of children with cochleovestibular malformations.

METHODS

Specialized electrodes were manufactured on the basis of three-dimensional data obtained from the high resolution computed tomography (HRCT) scans of the temporal bones of these two children. Electrode positioning was achieved with direct endoscopic view of the cavity utilizing a three-hole common cavity technique.

RESULTS

Optimal electrode positioning in apposition to the medial neuroepithelium in the common cavity was verified visually intraoperatively. Postoperatively, minimal stable electrical current levels were found to be required.

CONCLUSIONS

Custom-designed electrodes have the potential to offer improved results in children with common cavity malformations. Intraoperative direct positioning may further improve these results.

Pathophysiology of Meniere's syndrome: are symptoms caused by endolymphatic hydrops?

BACKGROUND

The association of Meniere's syndrome with endolymphatic hydrops has led to the formation of a central hypothesis: many possible etiologic factors lead to hydrops, and hydrops in turn generates the symptoms. However, this hypothesis of hydrops as being the final common pathway has not been proven conclusively.

SPECIFIC AIM

To examine human temporal bones with respect to the role of hydrops in causing symptoms in Meniere's syndrome. If the central hypothesis were true, every case of Meniere's syndrome should have hydrops and every case of hydrops should show the typical symptoms.

METHODS

Review of archival temporal bone cases with a clinical diagnosis of Meniere's syndrome (28 cases) or a histopathologic diagnosis of hydrops (79 cases).

RESULTS

All 28 cases with classical symptoms of Meniere's syndrome showed hydrops in at least one ear. However, the reverse was not true. There were 9 cases with idiopathic hydrops and 10 cases with secondary hydrops, but the patients did not exhibit the classic symptoms of Meniere's syndrome. A review of the literature revealed cases with asymptomatic hydrops (similar to the current study), as well as cases where symptoms of Meniere's syndrome existed during life but no hydrops was observed on histology. We also review recent experimental data where obstruction of the endolymphatic duct in guinea pigs resulted in cytochemical abnormalities within fibrocytes of the spiral ligament before development of hydrops. This result is consistent with the hypothesis that hydrops resulted from disordered fluid homeostasis caused by disruption of regulatory elements within the spiral ligament.

CONCLUSION

Endolymphatic hydrops should be considered as a histologic marker for Meniere's syndrome rather than being directly responsible for its symptoms.

Communication between the perilymphatic scalae and spiral ligament visualized by in vivo MRI

We evaluated the transport of Gadolinium-diethylenetriaminepentaacetate-bismethylamide (Gd-DTPA-BMA) through the round window (RW) membrane into the perilymphatic space with 4.7-T MRI in an animal study and 1.5-T MRI in humans. After administration of Gd-DTPA-BMA onto the intact RW membrane of guinea pig, Gd-DTPA-BMA uptake was observed in the basal turn and part of the second turn within 40 min. The scala tympani, scala vestibuli, the fibrous part of the spiral ligament and semicircular canal all showed uptake of Gd-DTPA-BMA. All turns of the cochlea were filled with Gd within 10 min in the perforated RW membrane administration group and within 30 min in the intravenous administration group. In patients who accepted middle ear injection of Gd-DTPA-BMA, uptake was observed within 2 h in the basal turn and semicircular canal. After 12 h the apex did still not show any uptake. Gd-DTPA-BMA is transported from the RW to the semicircular canal, the scala tympani and scala vestibuli without passing the helicotrema.