Observation of the external aperture of the vestibular aqueduct using three-dimensional surface reconstruction imaging

A possible mechanism of the formation of endolymphatic hydrops and its associated inner ear disorders

The pathology of Meniere's disease (MD) is well established to be endolymphatic hydrops. However, the mechanism underlying deafness and vertigo of MD or idiopathic endolymphatic hydrops is still unknown. In order to evaluate the pathogenesis of deafness and vertigo in MD, it seems to be rational to investigate the interrelationship between hydrops and inner ear disorders using animals with experimentally-induced endolymphatic hydrops. In spite of intense efforts by many researchers, the mechanism of vertiginous attack has been unexplained, because animals with experimental hydrops usually did not show vertiginous attack. Recently, there are two reports to succeed to evoke vertiginous attack in animals with experimental hydrops. In the present paper were first surveyed past proposals about underlying mechanism of the development of hydrops and inner ear disorders associated with hydrops, and were discussed the pathogenetic mechanism of vertiginous attack in hydrops. In conclusion, abrupt development of hydrops was thought to play a pivotal role in the onset of vertiginous seizure.

Volume-rendered computed tomography images of the surgical field for endolymphatic sac surgery

PURPOSE

Identification of the endolymphatic sac has failed occasionally. Postoperative complications have also rarely been reported. Given a safer and more reliable surgery, preoperative anatomical assessments are valuable, however, the vestibular aqueduct has seldom been seen with multi-planar reconstruction (MPR) computed tomography (CT) images yet. Our study aimed to determine the significance and utility of volume-rendered (VR) CT images of the surgical field for identifying the vestibular aqueduct, compared with MPR CT images.

SUBJECTS AND METHODS

14 patients with Meniere's disease who underwent endolymphatic sac surgery between 2008 and 2011. Location and size of the vestibular aqueduct were assessed using VR and MPR CT images, independently.

RESULTS

Accuracy of identifying the location differed significantly between VR and MPR CT images (rate of total correct evaluations: 100% by VR CT images vs 75% by MPR CT images, p = 0.02). Size was correctly identified in cases with a small endolymphatic sac using VR CT images (rate of total correct evaluations for size of the vestibular aqueduct: 100% by VR CT vs 57% by MPR CT, p = 0.046). VR CT images also demonstrated clearly the relationship between the endolymphatic sac and high jugular bulb. In two cases, the endolymphatic sac was identified by VR images, not by MPR images.

CONCLUSION

Accurate information about the location and size of vestibular aqueduct can allow sac surgeons to identify a tiny endolymphatic sac more easily and certainly, and also aids surgical trainees to learn sac surgery safely.

Magnetic resonance imaging findings in Ménière's disease

OBJECTIVES

To identify and evaluate cranial magnetic resonance imaging findings associated with Ménière's disease.

METHODS

Seventy-eight patients with a documented diagnosis of Ménière's disease and 35 controls underwent 1.5 T or 3 T magnetic resonance imaging of the brain. Patients also underwent otological, vestibular and audiometric examinations.

RESULTS

Lack of visualisation of the left and right vestibular aqueducts was identified as statistically significant amongst Ménière's disease patients (left, p = 0.0001, odds ratio = 0.02; right, p = 0.0004, odds ratio = 0.03). Both vestibular aqueducts were of abnormal size in the Ménière's disease group, albeit with left-sided significance (left, p = 0.008, odds ratio = 10.91; right, p = 0.49, odds ratio = 2.47).

CONCLUSION

Lack of vestibular aqueduct visualisation on magnetic resonance imaging was statistically significant in Ménière's disease patients compared to the general population. The study findings suggest that magnetic resonance imaging can be useful to rule out retrocochlear pathology and provide radiological data to support the clinical diagnosis of Ménière's disease.

Unilateral Enlarged Vestibular Aqueduct Syndrome and Bilateral Endolymphatic Hydrops

Enlarged vestibular aqueduct (EVA) syndrome is a common congenital inner ear malformation characterized by a vestibular aqueduct with a diameter larger than 1.5 mm, mixed or sensorineural hearing loss that ranges from mild to profound, and vestibular disorders that may be present with a range from mild imbalance to episodic objective vertigo. In our study, we present the case of a patient with unilateral enlarged vestibular aqueduct and bilateral endolymphatic hydrops (EH). EH was confirmed through anamnestic history and audiological exams; EVA was diagnosed using high-resolution CT scans and MRI images. Therapy included intratympanic infusion of corticosteroids with a significant hearing improvement, more evident in the ear contralateral to EVA. Although most probably unrelated, EVA and EH may present with similar symptoms and therefore the diagnostic workup should always include the proper steps to perform a correct diagnosis. Association between progression of hearing loss and head trauma in patients with a diagnosis of EVA syndrome is still uncertain; however, these individuals should be advised to avoid activities that increase intracranial pressure to prevent further hearing deterioration. Intratympanic treatment with steroids is a safe and well-tolerated procedure that has demonstrated its efficacy in hearing, tinnitus, and vertigo control in EH.

Comparison of Endolymphatic Duct Dimensions and Jugular Bulb Abnormalities Between Meniere Disease and a Normal Population

BACKGROUND

The pathogenesis of Meniere disease (MD) has not been fully understood. According to the widely accepted theory, imbalances due to overproduction and/or impaired absorption of endolymph may cause endolymphatic hydrops, which is the hallmark pathological finding in MD. Some developmental temporal bone abnormalities may impair endolymph circulation and absorption, and these abnormalities could be a part of MD pathophysiology. However, structural features of the temporal bone cannot explain MD pathophysiology definitively. The authors aimed to determine the length and width of the endolymphatic duct (ED) along with jugular bulb (JB) abnormalities in MD patients and normal controls using high-resolution computed tomography, and to discuss the results supporting and opposing endolymphatic hydrops based on the data obtained.

METHODS

Thirty-six ears of 18 patients with unilateral MD and 34 ears of 17 normal subjects were enrolled. Jugular bulb abnormalities and ED dimensions were evaluated in 3 groups: affected and unaffected ears of MD patients, and healthy controls. The ED dimensions and JB abnormalities were evaluated with high-resolution computed tomography.

RESULTS

The ED was found to be significantly shorter and narrower in the affected ears of the MD patients than in the healthy control group. In addition, more JB abnormalities were detected in the affected ears of the MD patients than in the healthy control group. However, there was no difference between the affected and unaffected ears of the MD patients.

CONCLUSION

Structural ED abnormalities and JB abnormalities may be predisposing factors for the development of Meniere disease, but cannot fully explain MD pathophysiology.

Large vestibular aqueduct syndrome and endolymphatic hydrops: two presentations of a common primary inner-ear dysfunction?

Objective:

To present the theory that large vestibular aqueduct syndrome (i.e. the recognised existence of an enlarged vestibular aqueduct with progressive sensorineural hearing loss) and endolymphatic hydrops are due to a common primary dysfunction of inner-ear fluid homeostasis.

Method:

Case report and review of the world literature concerning large vestibular aqueduct syndrome and endolymphatic hydrops.

Results:

We report a family in which one sibling suffered from large vestibular aqueduct syndrome while the other had classic Ménière's disease. This suggests that large vestibular aqueduct syndrome and endolymphatic hydrops, in some cases, may be due to a common primary dysfunction of inner-ear fluid homeostasis.

Conclusion:

To our knowledge, this is the first report in the world literature to postulate that variation in the relative compliance of inner-ear membranes could be the factor that determines the manifestation of the disorder as either endolymphatic hydrops or large vestibular aqueduct syndrome.

Three-dimensional cone beam computed tomography imaging of the membranous labyrinth in patients with Meniere's disease

CONCLUSION

Three-dimensional cone beam computed tomography (3DCT) images revealed characteristic malformations of the membranous labyrinth of the inner ear in Meniere's disease (MD). The morphology of the membranous region between the vestibular cecum of the cochlea and the saccule of ears with MD was compared to that of healthy ears. The present study supports the hypothesis proposed earlier that reuniting duct blockade is a result of the dislodgement of saccular otoconia.

OBJECTIVE

To visualize the membranous labyrinth using 3DCT and to investigate the pathology of MD.

METHODS

A preparatory study was conducted to determine the optimal 3DCT window settings for the detection of water, muscle, calcium carbonate (CaCO3), and bone. Based on this preparatory study, the ears of 13 healthy volunteers and 25 MD patients definitely diagnosed according to the criteria issued by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology, Head and Neck Surgery (AAO-HNS), were visualized.

RESULTS

The differences in the membranous labyrinth between MD ears and healthy ears could be visualized using 3DCT. The images were classified into three types based on their morphological pattern. The ears of patients with MD were different from normal ears in terms of this classification.

Relationship between multidetector CT imaging of the vestibular aqueduct and inner ear pathologies

This study investigated the relationships between morphological changes in the vestibular aqueduct (VA) in different inner ear pathologies. Eighty-eight patients (34 males and 54 females, ranging from seven to 88 years of age; average age 49.2 years) with cochleovestibular disorders underwent temporal bone CT (with a 64-channel helical CT system according to temporal bone protocol parameters; 0.6 mm slice thickness, 0.6 mm collimation, bone reconstruction algorithm). All patients with cochleovestibular disorders who underwent temporal bone CT had been previously divided into six different suspected clinical classes: A) suspected pathology of the third window; B) suspected retrocochlear hearing loss; C) defined Ménière's disease; D) labyrinth lithiasis; E) recurrent vertigo. On CT images we analyzed the length, width and morphology of the VA, contact between the VA and the jugular bulb (JB), the thickness of the osseous capsule covering the semicircular canals, the pneumatization rate of the temporal bone and the diameter of the internal auditory canal. At the end of the diagnostic work-up all patients were grouped into six pathological classes, represented as follow: 1) benign paroxysmal positional vertigo (BPPV), 2) recurrent vertigo (RV), 3) enlarged vestibular aqueduct syndrome (EVAS), 4) sudden or progressive unilateral sensorineural hearing loss (SNHL), 5) superior semicircular canal dehiscence syndrome (SSCD), 6) recurrent vestibulocochlear symptoms in Ménière's disease. We evaluated 176 temporal bones in 88 patients. The VA was clearly visualized in 166/176 temporal bones; in ten ears the VA was not visualized. In 14 ears (11 patients, in three of whom bilaterally) we found an enlarged VA while in 31 ears the VA was significantly narrower. In 16 ears a dehiscence of the JB with the vestibular or cochlear aqueduct was noted. In all six patients with suspected EVAS we found a AV wider than 1.5 mm on CT scans; moreover CT identified four patients with large VA and ill-defined clinical symptoms. Most patients with BPPV (11 patients, Class 1) we did not find any VA abnormalities on CT scans, confirming the clinical diagnosis in ten patients; in the remaining patients we found an enlarged VA, not clinically suspected. In the RV class (eight patients, Class 2) we found three patients with negative CT scans, two patients with narrow aqueduct and subsequently reclassified as Ménière's disease patients, and three patients with ectasic JB dehiscence with the VA. In patients suffering from SNHL we found no statistically significant correlation with the morphological abnormalities. The clinical suspicion of SSCD was confirmed by CT in 11/13 patients (84.6 %); in addition another seven patients showed a thinning or dehiscence of the superior semicircular canals as the prevailing alteration on CT scans, and were reclassified in this group. Ménière's disease symptoms were correlated with a VA alteration in more than half of the cases; the most striking finding in this class was that the VA was significantly narrower (21 patients). Our study demonstrates that alterations of the VA morphology are not only related to EVAS but are also found in other inner ear pathologies such as Ménière's disease. Furthermore, MDCT may confirm the presence of correlations between the morphology of inner ear structures such as VA, semicircular canals or JB dehiscence, and alterations of vestibulocochlear function.

Blockage pattern of longitudinal flow in Meniere's disease

CONCLUSION

In the present study, classification of the patterns of 3D CT images of the ductus reuniens (reuniting duct) (RD), saccular duct (SD), and endolymphatic sinus (ES) gave more precise information for assessing the pathological condition of Meniere's disease (MD) than our previous study.

OBJECTIVE

This study attempted to provide more detailed information on MD by classifying the patterns of 3D CT images of the RD, SD, and ES in patients with MD.

METHODS

We examined the ears of 62 patients with definitely diagnosed unilateral MD based on the criteria of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) using 3D CT. The 3D CT images of bony grooves of RD, SD, and ES (BRD, BSD, and BES) were classified into patterns according to aspects of their patency.

RESULTS

BRD could be classified into six types by assessing their patency defined using the criteria in this study. In the ears on the affected side of patients with MD, the BRD, BSD, and BES lost continuity in 3D CT images along their bony routes and were significantly different from normal healthy ears (p < 0.01). There were no significant differences among each stage of MD in the distributions of BRD and BES except for BSD.

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).

Visualization and assessment of saccular duct and endolymphatic sinus

CONCLUSION

The saccular duct and endolymphatic sinus run in the bony groove, before reaching the orifice of the vestibular aqueduct. We first clinically visualized this sulciform groove using three-dimensional (3D) cone beam CT images. This strategy can be useful to assess the condition of the saccular duct and endolymphatic sinus concerning the longitudinal flow system of endolymph.

OBJECTIVE

To assess the saccular duct and endolymphatic sinus in the endolymphatic system in order to advance clinical studies on inner ear dysfunction.

METHODS

The sulciform groove of the saccular duct and endolymphatic sinus of human subjects was analyzed by cone beam CT and compared with that of a cadaver.

RESULTS

We could obtain reconstructed 3D CT images of the sulciform groove of the saccular duct and endolymphatic sinus using several CT window levels.

Three-dimensional images of the reuniting duct using cone beam CT

CONCLUSION

There is a bony groove under the course of the reuniting duct of the inner ear. Cone beam CT could show three-dimensional (3D) reconstruction images of this groove in a cadaver and living human subjects.

OBJECTIVE

To obtain simple and universal images of the reuniting duct in humans for clinical use.

MATERIALS AND METHODS

We investigated the reuniting duct macroscopically by observing the temporal bone in cadavers and living human subjects using cone beam CT. 3D reconstruction images of the duct were analyzed by the rendering software IVIEW.

RESULTS

The reuniting duct showed a bony groove between the saccule and cecum of the hook portion of the cochlea that could be three-dimensionally visualized by cone beam CT. A bony groove image in a living human subject could also be visualized by cone beam CT.

Relationship of vestibular aqueduct and inner ear pressure in Ménière's disease and the normal population

OBJECTIVE

Etiopathogenesis of Ménière's disease has not been resolved. The principal histopathologic finding in this disease is endolymphatic hydrops. The majority of radiologic and histopathologic studies demonstrated a narrow vestibular aqueduct in Ménière's disease. There is no study in the literature investigating the relationship between inner ear pressure and vestibular aqueduct dimensions. Static acoustic compliance is a noninvasive procedure that is thought to measure perilymphatic pressure at the footplate. An increase in mechanical fluid pressure in the inner ear is transmitted to the footplate of the stapes. This causes a reduction in the compliance at the drum. The aim of this study is to investigate the relationship between vestibular aqueduct dimensions and static acoustic compliance in Ménière's disease and the normal population.

STUDY DESIGN

Prospective study.

METHODS

Forty patients with Ménière's disease and 40 healthy individuals with no otolaryngologic disorders were the subjects of this study. Each group was further divided into two according to static compliance value (normal and low static compliance). In these four groups dimensions of vestibular aqueduct were determined radiologically by high-resolution computerized tomography and correlated with normal and low static acoustic compliance values (normal and high perilymphatic pressure).

RESULTS

The results demonstrated that vestibular aqueduct is narrower in patients with Ménière's disease than the normal population. However, there is no relationship between vestibular aqueduct dimensions and inner ear pressure obtained by static acoustic compliance measurements.

Computer-assisted three-dimensional reconstruction of head and neck tumors

OBJECTIVE

Because head and neck tumors reside in a complex area, having a three-dimensional (3-D) model of the patient's unique anatomical features may assist in the delineation of pathology. The authors describe a new computer technique of 3-D anatomical reconstruction from two-dimensional computed tomography (CT) and magnetic resonance (MR) data and discuss how it represents a step forward in the continuing evolution of 3-D imaging.

STUDY DESIGN

The authors selected three patients with solitary head and neck tumors and reconstructed their anatomy in a 3-D format for study. The tumors represented locations in the nose and central skull base (patient 1), temporal bone (patient 2), and neck (patient 3).

MATERIALS AND METHODS

MR and CT images from the individual patients were electronically transferred to workstations in the Surgical Planning Laboratory of the authors' institution. Registration (or fusion) was carried out between the MR and CT images. The desired anatomic components underwent segmentation (identification and isolation). Assembly of the segmented images was performed and the resulting structures were integrated to produce a 3-D model.

RESULTS

3-D models of the following were constructed and displayed in an interactive format on high-capacity computer workstations: 1) a skull base sarcoma with extension into the nasopharynx and nose; 2) an acoustic neuroma with internal auditory canal involvement; and 3) a metastatic recurrence of a tongue base squamous cell carcinoma in the posterior triangle of the right side of the neck with extension to the skull base.

CONCLUSION

The authors' Surgical Planning Laboratory has developed a 3-D reconstruction technique that has several new features. The models provided a very good 3-D interactive representation of the tumors and patient anatomy. The need now exists to develop this method of 3-D reconstruction of head and neck tumors for potential applications in treatment, research, and medical education.

Sensorineural hearing loss in patients with large vestibular aqueduct

In examining 181 patients (327 ears) with sensorineural hearing loss of unknown etiology and 25 people (50 ears) with normal hearing by high-resolution computed tomography (CT), the image of the large vestibular aqueduct (VA) was defined as being a visible large aperture (> or = 4 mm), and small distance between vestibule and traceable part of the VA nearest to the vestibule (> or = 1 mm). The large VA was found in 13 patients (23 ears, 7.0%); it was relatively frequent following hypoplastic cochlea (33 ears, 10.1%) in all the inner ear anomalies detected. In patients with large VA, high-frequency hearing was affected more than low frequency, and history of sudden hearing loss was observed frequently (61% of ears with large VA), which was found to be triggered by characteristic episodes such as minor head trauma, etc. Those clinical features were observed more in those without cochlear anomaly than in those accompanying cochlear anomaly. Pathogenesis of sensorineural hearing loss and characteristic fluctuation of hearing in those patients are discussed.

Optimization of submillimeter-resolution MR imaging methods for the inner ear

Submillimeter-resolution magnetic resonance (MR) imaging of the inner ear is valuable for diagnosis and treatment planning. Its main advantage for investigations of underlying disease is that it can directly depict the fluid spaces of the membranous labyrinth rather than define only the bony canal, as does computed tomography. A systematic evaluation of factors influencing high-resolution three-dimensional (3D) gradient-echo imaging of the inner ear with a standard clinical MR system is presented. This includes the evaluation of various radio-frequency coils, the design of steady-state pulse sequences, and the optimization of acquisition parameters. A quantitative analysis was facilitated by computer simulations and image processing. The highest signal-to-noise ratio for the membranous labyrinth was obtained with a single 3-inch (7.6-cm) receiver coil and a 3D GRASS (gradient-recalled acquisition in the steady state) sequence with the minimal achievable TR msec/TE msec of 25/7 and a 40 degrees--60 degrees flip angle, which yielded acceptable images with minimal voxel volumes of 0.1 mm3 in 14 minutes.

Clinical usefulness of three-dimensional reconstruction of the temporal bone from CT scans in cholesteatoma cases

The importance of computed tomography (CT) in analyzing temporal bone diseases has increased, and the ability to reconstruct the temporal bone structures in three dimensions from multiple CT films has been required. In order to facilitate the visualization of temporal bone structures, we tried reconstructing temporal bone CT images three-dimensionally using a personal computer, and evaluated the possibility of using three-dimensional CT images clinically. Temporal bone CT scan films from five cases of cholesteatoma and a case of otosclerosis as control were examined. Four temporal bone structures (temporal bone contour, middle ear, mastoid, and inner ear) and cholesteatoma, extracted from enlarged black and white CT films, were inputted to the personal computer. Data import and image reconstruction procedures were performed using commercially available software. Our results indicate that three-dimensional reconstructions contribute to visualizing temporal bone structures spatially, and to choosing surgical approaches in difficult cases, such as petrous bone cholesteatoma. In conclusion, three-dimensional reconstructions using a personal computer is useful in the diagnosis and treatment of cholesteatoma.

Development of the vestibular aqueduct in Menière's disease

The external aperture width of the vestibular aqueduct was measured in living subjects of various ages, with normal and diseased ears. Measurements were made from 3-dimensional reconstruction of CT images, and the developmental process was studied. The following results were obtained. i) In Menière's disease the external aperture was hypoplastic and its width significantly smaller than that in normal individuals and those with chronic otitis media, including children. ii) There were no significant differences between normal ears and ears with chronic otitis media in either adults or children. The development of external aperture was completed in childhood. iii) In Menière's disease, hypoplasia evidently begins before childhood, which suggests that congenital factors are involved in the pathology of this disease.

Investigation of the external aperture of the vestibular aqueduct in Menière's disease by three-dimensional image analysis

The width of the external aperture of the vestibular aqueduct was measured in patients with Meniere's disease using three-dimensional images. The width of the aperture on the affected side was significantly smaller compared with that in normal ears or ears with chronic otitis media. Also, the width of the aperture on the opposite (healthy) side in unilateral Meniere's disease was significantly smaller than in these two other groups. These findings suggest that the aqueduct is incompletely developed in patients with Meniere's disease and that this may be related to the pathogenesis of this condition. Also, in unilateral Meniere's disease the opposite ear runs a high risk of eventually developing the disease.