Cochlear aqueduct revisited: A histological study using human fetuses.

BACKGROUND AND AIM: The cochlear aqueduct (CA) connects between the perilymphatic space of the cochlea and the subarachnoid space in the posterior cranial fossa. The study aimed to examine 1) whether cavitation of the CA occurs on the subarachnoid side or the cochlear side and 2) the growth and/or degeneration of the CA and its concomitant vein. METHODS: We examined paraffin-embedded histological sections from human fetuses: 15 midterm fetuses (crown-rump length or CRL, 39-115 mm) and 12 near-term fetuses (CRL, 225-328 mm). RESULTS: A linear mesenchymal condensation, i.e., a likely candidate of the CA anlage, was observed without the accompanying vein at 9-10 weeks. The vein appeared until 15 weeks, but it was sometimes distant from the CA. At 10-12 weeks, the subarachnoid space (or the epidural space) near the glossopharyngeal nerve rapidly protruded into the CA anlage and reached the scala tympani, in which cavitation was gradually on-going but without epithelial lining. However, CA cavitation did not to occur in the anlage. At the opening to the scala, the epithelial-like lining of the CA lost its meningeal structure. At near-term, the CA was often narrowed and obliterated. CONCLUSION: The CA develops from meningeal tissues when the cavitation of the scala begins. The latter cavitation seemed to reduce tissue stiffness leading, to meningeal protrusion. The so-called anlage of CA might be a phylogenetic remnant of the glossopharyngeal nerve branch. A course of cochlear veins appears to be determined by a rule different from the CA development.

Computed tomographic 3D analysis of the cochlear aqueduct-potential and limitations of clinical imaging.

Background: The cochlear aqueduct (CA), which connects the scala tympani and the subarachnoid space, and its accompanying structures appear to have a significant relevance during cochlear implantation and an accurate visualization in clinical imaging is of great interest. Aims and Objective: This study aims to determine which potential and limitations clinically available imaging modalities have in the visualization of the CA. Methods: Micro-CT, flat-panel volume computed tomography with and without secondary reconstruction (fpVCT, fpVCTseco) and multislice computed tomography (MSCT) of 10 temporal bone specimen were used for 3D analysis of the CA. Results: FpVCTseco proved superior in visualizing the associated structures and lateral portions of the CA, which merge into the basal turn of the cochlea. All clinical imaging modalities proved equal in analyzing the length, total volume of the CA and its area of the medial orifice. Conclusion: The choice of the most accurate clinical imaging modality to evaluate the CA and its associated structures depends on the clinical or scientific question. Furthermore, this study should provide a basis for further investigations analyzing the CA.

Does otosclerosis affect the dimensions of the facial canal and cochlear aquaduct?

PURPOSE: Our aim was to evaluate the relationship of the dimensions of the facial canal (FC) and cochlear aqueduct (CA) in otosclerosis (OS) with the type and severity of OS. METHODS: Two radiologists retrospectively evaluated temporal bone high-resolution computed tomography (HRCT) images obtained from 48 healthy individuals and 94 OS patients between January 2015 and July 2020. In the study group, the CA width, funnel base width, and funnel length, in addition to the FC transverse length, were measured in the axial plane. The CA length was measured in the coronal plane on HRCT images. The FC craniocaudal length was measured in the same plane as the fissula ante fenestram (FAF) in coronal reformatted HRCT images. Grading of OS was based on otosclerotic plaque density and new bone formation extending toward the tympanic cavity at the FAF level. RESULTS: In the OS patients, the CA width and FC craniocaudal and FC transverse diameters were significantly decreased on both sides compared to those in the control group (p < 0.001). In fenestral OS, the FC craniocaudal and transverse widths on both sides were statistically significantly lower than the FC widths in the control group (p < 0.0001). A statistically negative correlation was found in the FC craniocaudal (r = - 0.831/- 0.818) and transverse (r = - 0.742/- 0.750) measurements on both sides in accordance with an increase in the otosclerotic plaque density (p < 0.0001). CONCLUSION: The presence of narrowing in the FC and CA adjacent to the FAF supports the role of autoimmunity theory in the etiology of OS.

Radiologic Evaluation of the Round Window Niche Configuration: A One-Stop Approach.

BACKGROUND: Preoperative radiological prediction of the round window niche configuration. METHODS: Fifty patients were evaluated. A single-axial high-resolution computed tomography image at the level of the cochlear aqueduct was compared to the intraoperative surgical images. Radiological configuration was classified as open, hooded, or covered depending on the extent of bony overhang. Surgical images were processed using Image J software to determine the amount of drilling required before the round window membrane is exposed. These images were classified according to the St. Thomas classification into 3 grades. RESULTS: In all patients, the axial cut showing the cochlear aqueduct was obtained. There were 12 cases in the open category, 17 in the hooded category, and 21 in the covered one. Intraoperatively, the actual findings were type I 12, type II 18, and type III 20. The correspondence between the expected and actual classification was correct in 8, 12, and 18 cases, respectively. Comparing the intraoperative findings with the expected radiological configuration, there was a good concordance with a statistically non-significant difference ( χ2=0.2613; P=.87751). CONCLUSION: It is possible to predict the configuration of the round window niche on a single-axial computed tomography cut and plan the most suitable axis of approach and predict the amount of drilling expected to expose the round window membrane.

Why did we encounter gusher in a stapes surgery case? Was it enlarged medial aperture of the cochlear aqueduct?

BACKGROUND AND PURPOSE: Preoperative prediction of cerebrospinal fluid (CSF) gusher is important for stapes surgery. According to the current opinion settled among otologists and radiologists, the issues of whether enlarged cochlear aqueduct might be a cause of CSF gusher in stapes surgery and which segment of the aqueduct should be taken into account to diagnose enlarged cochlear aqueduct in computerized tomography (CT) are controversial. The case we encountered led us to hypothesize that enlarged cochlear aqueduct might cause CSF gusher in stapes surgery and that shape and diameter of medial aperture of the cochlear aqueduct are important in this prediction. METHODS AND RESULTS: Enlarged medial aperture of the cochlear aqueduct with a shape differed from that of the other side was retrospectively diagnosed in thin-slice CT in a patient who had been undergone middle ear and stapes surgery for conductive hearing loss. This finding went unnoticed in preoperative CT. In the small fenestra stapedotomy operation, CSF gusher occurred through opening in the ill-defined, fixed and thickened stapes footplate. A piece of temporalis fascia and reshaped incus were appropriately placed which stopped the gusher. Re-evaluation of preoperatively taken CT showed that anterior-posterior and superior-inferior diameters of the medial aperture were 11.7 mm and 2.87 mm in CSF gusher side versus 2.95 mm and 1.88 mm on the other side, respectively. Its shape in gusher side differed from that of the other side. CONCLUSION: This report is the first to show video-documented CSF gusher in a patient with enlarged medial aperture of the cochlear aqueduct. It appears to be plausible to propose that these findings have to change the otologists' and radiologists' perspective to the cochlear aqueduct. It can be deduced that difference in shapes of the medial aperture in both sides might be an indicator of potential CSF gusher.

Anatomy of the Round Window Region With Relation to Selection of Entry Site Into the Scala Tympani.

OBJECTIVES/HYPOTHESIS: The aim of cochlear implantation is to safely insert an electrode array into the scala tympani (ST) while avoiding damage to surrounding structures. There is disagreement on the optimal way of entering the ST-the round window (RW) approach versus cochleostomy. Regardless of the chosen approach, it is vital to understand the regional anatomy, which is complex, difficult to conceptualize, and rarely dissected in temporal bone courses. The goal of this study was to examine the anatomy of the RW to gain more in-depth knowledge on the local relationships of the anatomical structures and propose an approach for entering the ST in cochlear implant surgery tailored to the encountered anatomy. STUDY DESIGN: Cadaveric prevalence study and expert opinion with literature review. METHODS: Cadaveric temporal bone dissection (n = 13) by the first author assessing the RW anatomy. RESULTS: The round window membrane (RWM) and the osseous spiral lamina (OSL) are curved structures, each with a horizontal and a vertical part. The two horizontal portions are very closely apposed. The relationship between the OSL and the RWM determines the best site for a cochleostomy, which if required is best placed anteroinferiorly to the RWM. The distance between the oval window inferior margin and the RW membrane is less than 2 to 3 mm. The ST initially extends inferiorly and medially to the RW. CONCLUSIONS: The findings of our dissection have implications for cochlear implant surgery in aiming to avoid trauma to the OSL and basilar membrane and aid decision making in choosing the safest surgical approach. LEVEL OF EVIDENCE: 5. Laryngoscope, 131:E598-E604, 2021.

Relationship Between the Cochlear Aqueduct and Internal Auditory Canal: Surgical Implications for Transcanal Transpromontorial Approaches to the Lateral Skull Base.

HYPOTHESIS: The cochlear aqueduct (CA) is subject to considerable anatomical variability. We hypothesize a topographical relationship between the CA and the internal auditory canal (IAC). BACKGROUND: The CA represents the lower limit of dissection during transcanal transpromontorial approaches to the lateral skull base due to its close relationship to the lower cranial nerves and jugular vein. METHODS: Three-dimensional models from high-resolution computed tomography scans of normal human temporal bones were created using threshold-based segmentation. The CA was classified into four categories. Five points were determined on the three-dimensional models to measure the surgically relevant relationships. RESULTS: Segmentation was performed on 26 high-resolution computed tomography scans. The average length of the virtual and visual part of the CA was 6.6 mm (SD ±1.7 mm) and 5.5 mm (SD ±1.3 mm) respectively. The mean distance between the IAC and the medial end of the visual part of the CA was 3.8 mm (±0.7 mm), while the average distance between the IAC and the lateral end was 1.4 mm (±0.6 mm). The distance between the visual part of the CA and the IAC increased by 0.25 mm per from the fundus of the IAC. CONCLUSION: A close relationship between the CA and the IAC could be established, despite the anatomical variability of the CA. The distance between CA and IAC increases by 0.25 per mm from the fundus to the porus of the IAC. These findings quantify the inferior limit of dissection of the transcanal transpromontorial approach to the lateral skull base.

Oval window perilymph fistula in child with recurrent meningitis and unilateral hearing loss.

A 2-year-old boy presented to Ears, Nose and Throat (ENT) surgeons with unilateral hearing loss. Following a prodrome of upper respiratory tract infection (URTI), he developed two episodes of pneumococcal meningitis in quick succession. This case demonstrates an unusual cause of perilymph fistula diagnosed on imaging and confirmed surgically. He had failed the Newborn Hearing Screening Programme and was therefore referred to audiology, who confirmed profound sensorineural hearing loss in the right ear. MRI showed incomplete partitioning (type 1) of the right cochlea, suggesting cerebrospinal fluid (CSF) leak from the region of the stapes. Exploratory tympanotomy confirmed this, and proceeded to CSF leak repair, obliteration of the Eustachian tube, subtotal petrosectomy, abdominal fat grafting and blind sac closure. Although middle ear effusions are common; particularly in children with recent URTI, the possibility of otogenic CSF leak needs to be considered, especially in cases of recurrent meningitis.

Involvement of the Cochlear Aqueduct by Jugular Paraganglioma Is Associated With Sensorineural Hearing Loss.

OBJECTIVE: The etiology of sensorineural hearing loss (SNHL) in patients with jugular paraganglioma (JP) whose tumors lack inner ear fistulae or vestibulocochlear nerve involvement is unknown. Recent literature has proposed that occlusion of the inferior cochlear vein may be causative. Herein, we assess the association between radiologic involvement of the cochlear aqueduct (CA) and the development of SNHL. STUDY DESIGN: Blinded, retrospective review of imaging and audiometry. SETTING: Tertiary center. PATIENTS: Adults with JP. INTERVENTION(S): None. MAIN OUTCOME MEASURES: Asymmetric SNHL was assessed continuously as the difference in bone conduction pure-tone average (BCPTA) between ears and as a categorical variable (≥15 dB difference at two consecutive frequencies, or a difference in speech discrimination score of ≥15%). Involvement of the CA was considered present if there was evidence of medial T2 fluid signal loss, contrast enhancement, or bony erosion/expansion. RESULTS: Of 30 patients meeting inclusion criteria, 15 (50%) had asymmetric SNHL. CA involvement was observed in 87% of patients with asymmetric SNHL compared with 13% in those with symmetric hearing (p = 0.0001). Univariate analysis demonstrated that age, sex, and tumor volume were not associated with asymmetric SNHL. The median difference in BCPTA between ears in patients with CA involvement was 21.3 dB HL compared to 1.2 dB HL in those without CA involvement (p < 0.0001). Regression analysis demonstrates that enhancement within the CA is associated with a BCPTA difference of 19.4 dB HL (p = 0.0006). CONCLUSIONS: Cochlear aqueduct involvement by JP is associated with SNHL in the absence of inner ear fistula, vestibulocochlear nerve involvement, or brainstem compression. Correlation with operative findings or histopathologic evidence of tumor involvement may validate this intriguing imaging finding.

Unified cochlear model for low- and high-frequency mammalian hearing.

The spatial variations of the intricate cytoarchitecture, fluid scalae, and mechano-electric transduction in the mammalian cochlea have long been postulated to provide the organ with the ability to perform a real-time, time-frequency processing of sound. However, the precise manner by which this tripartite coupling enables the exquisite cochlear filtering has yet to be articulated in a base-to-apex mathematical model. Moreover, while sound-evoked tuning curves derived from mechanical gains are excellent surrogates for auditory nerve fiber thresholds at the base of the cochlea, this correlation fails at the apex. The key factors influencing the divergence of both mechanical and neural tuning at the apex, as well as the spatial variation of mechanical tuning, are incompletely understood. We develop a model that shows that the mechanical effects arising from the combination of the taper of the cochlear scalae and the spatial variation of the cytoarchitecture of the cochlea provide robust mechanisms that modulate the outer hair cell-mediated active response and provide the basis for the transition of the mechanical gain spectra along the cochlear spiral. Further, the model predicts that the neural tuning at the base is primarily governed by the mechanical filtering of the cochlear partition. At the apex, microscale fluid dynamics and nanoscale channel dynamics must also be invoked to describe the threshold neural tuning for low frequencies. Overall, the model delineates a physiological basis for the difference between basal and apical gain seen in experiments and provides a coherent description of high- and low-frequency cochlear tuning.

High-Resolution Computed Tomography of the Inner Ear: Effect of Otosclerosis on Cochlear Aqueduct Dimensions.

OBJECTIVES: The cochlear aqueduct is a bony duct connecting the scala tympani with the subarachnoid space. Given the pathophysiology of otosclerosis, including bone resorption and new bone deposition, we hypothesize that the cochlear aqueduct in otosclerotic ears is narrowed. METHODS: A retrospective review of patients with otosclerosis who have undergone high-resolution computed tomography (HRCT) of the temporal bone was completed. The control cohort included 20 patients with the diagnosis of noise-induced hearing loss, without the diagnosis of otosclerosis. Uniform measurements of cochlear aqueduct dimensions were performed using the axial plane. RESULTS: The otosclerosis cohort included 25 males and 52 females with mean age of 52.2 ± 17.6 years. The control group included 10 males and 10 females with mean age of 64.0 ± 18.5 years. The mean cochlear aqueduct length, width mid canal, aperture base, aperture widest diameter, and funnel diameter in millimeters were 12.19 ± 1.66, 0.68 ± 0.28, 4.21 ± 1.67, 3.23 ± 1.47, and 2.70 ± 1.05 in the ears with otosclerotic foci and 11.57 ± 1.66, 0.69 ± 0.29, 2.56 ± 1.59, 2.77 ± 1.67, and 2.58 ± 1.03 in control group, respectively. Statistical difference was seen in length of cochlear aqueduct, aperture base, and aperture widest diameters (P = .017, <.001, .007). CONCLUSIONS: The length of the cochlear aqueduct and the funnel width are statistically longer in the otosclerotic population compared to control. The width of the cochlear aqueduct is not statistically different.

Perilymphatic fistula and pneumolabyrinth without temporal bone fracture: a rare entity.

Post-traumatic pneumolabyrinth is an uncommon clinical entity, particularly in the absence of temporal bone fracture. We report the case of a patient who presented to our emergency department with a headache, sudden left hearing loss and severe dizziness which began after a traumatic brain injury 3 days earlier. On examination, the patient presented signs of left vestibulopathy, left sensorineural hearing loss and positive fistula test, normal otoscopy and without focal neurological signs. The audiometry confirmed profound left sensorineural hearing loss. Cranial CT revealed a right occipital bone fracture and left frontal subdural haematoma, without signs of temporal bone fracture. Temporal bone high-resolution CT scan revealed left pneumolabyrinth affecting the vestibule and cochlea. Exploratory tympanotomy revealed perilymphatic fistula at the location of the round window. The sealing of defect was performed using lobule fat and fibrin glue. He presented complete resolution of the vestibular complaints, though the hearing thresholds remained stable.

Atraumatic Scala Tympani Cochleostomy; Resolution of the Dilemma.

OBJECTIVES: While an accurate placement in cochleostomy is critical to ensure appropriate insertion of the cochlear implant (CI) electrode into the scala tympani (ST), the choice of preferred cochleostomy sites widely varied among experienced surgeons. We present a novel technique for precise yet readily applicable localization of the optimum site for performing ST cochleostomy. MATERIAL AND METHODS: Twenty fresh frozen temporal bones were dissected using the mastoidectomy-posterior tympanotomy approach. Based on the facial nerve and the margins of the round window membrane (RWM), the cochleostomy site was chosen to insert the electrode into the ST while preserving the surrounding intracochlear structures. RESULTS: There is a limited safe area suitable for the ST implantation in the area inferior and anterior to the RWM. There is a higher risk of scala vestibuli (SV) insertion anterior to that area. Posterior to that area, the cochlear aqueduct (CA) and inferior cochlear vein (ICV) are liable for the injury. CONCLUSION: For atraumatic CI, precise and easy localization of the site of cochleostomy play a pivotal role in preserving intracochlear structures. Accurate setting of the vertical and horizontal orientations is mandatory before choosing the site of cochleostomy. The facial nerve and the margins of the RWM offer a very helpful clue for such localization; meanwhile, it is readily identifiable in the surgical field.

Anatomical Variations in Patients with Ménière Disease: A Tomography Study

Abstract Introduction The etiology of Ménière disease (MD), a difficult-to-treat condition with great morbidity, remains controversial in the literature. The possible clinical and diagnostic impact of anatomical variations of the temporal bone among patients with MD has been recently studied. Objective To identify anatomical variations of the temporal bone associated with the diagnosis of MD. Methods Thirty-seven patients were included, although each ear was considered separately (n = 74). A case group (nA = 33) was composed of the affected ears of patients with definiteMDand a control group (nB = 41) was used consisting of the ears of individuals who did not meet the criteria for MD and of the contralateral ears from patients with unilateral disease. Tomographic images from the individuals included in the study were submitted to a blinded and systematic evaluation regarding a broad variety of anatomical variations of the temporal bone. Obtained data were compared statistically between the groups and after stratifying the study sample. Significance level was set at 0.05. Results Among the affected ears, it was observed an increased number of tomographic scans in which the vestibular aqueduct could not be identified (p = 0.01, Fisher exact test). No statistically significant differences were observed when comparing the affected and contralateral ears frompatients with unilateral MD, between affected ears from patients with unilateral and bilateral disease or between contralateral ears of patients with unilateral affection and patients without the disease. Conclusion Some anatomical variations might be more frequent in the affected ears of patients with MD, such as the lower rates of individualization of the vestibular aqueduct.

Sneezing and Perilymphatic Fistula of the Round Window: Case Report and Systematic Review of the Literature.

The goal of the present study was to describe a case of perilymphatic fistula (PLF) of the round window (RW) that occurred after sneezing, along with a review of the literature. We report a case of PLF of RW, which was provoked by sneezing, and its consequent medical and surgical treatments. With respect to the review of the literature, articles were initially selected based on their titles or abstracts, followed by methodological evaluation. The patient underwent an explorative tympanotomy (ET) with packaging of RW with the pericondrium, following which the patient's complaints regarding vertigo and imbalance disappeared, but the severe sensorineural hearing loss persisted. For the literature review, five references were selected. These studies showed a great variety in the clinical presentation and healing of symptoms. Sneezing represents a rare but well-recognized cause of PLF, as reported in our case. The correct selection of patients who should undergo ET and an early surgical repair of PLF are mandatory for better outcomes, especially in case of hearing.

The Human Cochlear Aqueduct and Accessory Canals: a Micro-CT Analysis Using a 3D Reconstruction Paradigm.

OBJECTIVE: We sought to study the anatomic variations of the cochlear aqueduct and its accessory canals in human temporal bones using micro-CT and a 3D reconstruction paradigm. More knowledge about the anatomic variations of these structures, particularly at the basal turn of the cochlea and round window niche, may be important to better preserve residual hearing as well as the neural supply during cochlear implant surgery. METHODS: An archival collection of 30 human temporal bones underwent micro-CT and 3D reconstruction. A surface enhancement paradigm was applied. The application displays reconstructed slices as a 3D object with realistic 3D visualization of scanned objects. Virtual sectioning or "cropping" of the petrous bone presented subsequent areas. Thereby, the bony canals could be followed from inside the basal turn of cochlea and middle ear to the jugular foramen. RESULTS: The cochlear aqueduct was always paralleled by an accessory canal containing the inferior cochlear vein. It ran from the basal turn of the cochlea and exited laterally in the jugular foramen. In 70% of the cases, a secondary accessory canal was observed and it derived mostly from a depression or infundibulum located in the floor of the round window niche. This canal also exited in the jugular foramen. The secondary accessory canal occasionally anastomosed with the primary accessory canal suggesting that it contains a vein that drains middle ear blood to the cranial sinus. CONCLUSION: Micro-CT with 3D surface reconstruction paradigm offers new possibilities to study the topographic anatomy of minor details in the human inner ear. The technique creates simulated transparent "castings" of the labyrinth with a coinciding surface view through enhancement of contrast between boundaries. Accessory canals that drain blood from the cochlea, spiral ganglion, and middle ear could be characterized three-dimensionally.

Micro-CT study of the human cochlear aqueduct.

OBJECTIVE: The anatomic structure of the cochlear aqueduct (CA) in human temporal bone specimens was observed using micro-computed tomography (CT). MATERIALS AND METHODS: Micro-CT scanning of 18-µm-thick slices was performed on 30 slides of human temporal bone specimens to observe the CA structure and its relationship with its surroundings. The length, internal and external apertures, and the narrowest width of the CA were measured. The differences in CAs were compared between high jugular bulb (HJB) specimens and normal specimens. RESULTS: A large number of CA images were acquired using Micro-CT scanning, which clearly displayed the basic anatomic structures, stereotactic localizations, and adjacent relationships of the CAs. The whole course of a CA was 12.31 ± 3.60 mm, the diameter of the internal aperture was 465 ± 242 µm, the diameter of the external aperture was 2.88 ± 1.06 mm, the narrowest diameter was 601 ± 335 µm, the diameter of the opening of inferior cochlear vein (ICV) was 151 ± 50 µm, the distance between the internal aperture and ICV was 270 ± 197 µm, and the distance between the inferior margin of the internal acoustic meatus (IAM) and the top most part of the external aperture of the CA was 6.783 ± 2.15 mm. No bony obstruction of the CA or CA enlargement was observed in the specimens. A total of 28 CAs had one accompanying bony canal in the surroundings. The length and travelling of the CA were not affected by the level of the jugular bulb (JB). The variation of the travelling of the ICV was larger than that of the CA. CONCLUSION: Micro-CT adequately displayed the bony CA canal and provided a new method for anatomical studies of the CA and a basis for functional studies.

The role of explorative tympanotomy in patients with sudden sensorineural hearing loss with and without perilymphatic fistula.

PURPOSE: The purpose of this study was to describe the role of explorative tympanotomy in patients with Profound Sudden Sensorineural Hearing Loss (SSNHL) without clinical evidence of perilymphatic or labyrinthine fistula and to compare intraoperative findings with the postoperative hearing outcome. STUDY DESIGN: Retrospective study of all patients diagnosed with SSNHL who underwent explorative tympanotomy between 2002 and 2005. SETTINGS: Tertiary care university-affiliated hospital. SUBJECTS AND METHODS: Eighty-two patients were diagnosed with unilateral profound SSNHL and underwent tympanotomy with sealing of the round and oval windows. Values of pure tone audiograms and percentage hearing loss of patients with and without intraoperative diagnosed perilymphatic fistula (PLF) were compared and analyzed. RESULTS: PLF was diagnosed in 28% cases intraoperatively. In most cases, hearing improved significantly after surgery. Interestingly, patients with PLF had a 2.4 times greater decrease of percentage hearing loss compared to patients without PLF. CONCLUSIONS: Explorative tympanotomy seems to be useful in patients with profound SSNHL. Patients with PLF benefit more from the surgical procedure and have better outcome than patients without PLF.

Improved HYDROPS: Imaging of Endolymphatic Hydrops after Intravenous Administration of Gadolinium.

To improve the imaging protocol for the evaluation of endolymphatic hydrops after intravenous administration of a gadolinium-based contrast agent, we modified our previously reported hybrid of reversed image of positive endolymph signal and native image of positive perilymph signal (HYDROPS) method. Although the scan time of the new protocol was half that of the previous one, there were no significant differences between two protocols in the mean contrast noise ratio between the endolymph and perilymph and the area ratio of the endolymph size values in nine patients.