Three-dimensional course of the vestibular aqueduct

2D Measurements of the Angle of the Vestibular Aqueduct Using CT Imaging

Recently, Bächinger et al. developed a software that measures the angle between the vestibular aqueduct proximal to the vestibule and the distal vestibular aqueduct on computed tomography (CT) scans and found differences in the vestibular aqueduct angle between the hypoplastic and degenerative categories of Meniere’s disease (MD). Hypoplastic radiological findings were associated with the development of bilateral MD and hypoplastic changes were not found outside of fetal temporal bones and individuals with MD. The purpose of this study is to examine how the software developed by Bächinger et al. performs when applied to a large dataset of adult patients with varied otologic diagnoses. Adult patients who underwent high resolution flat panel CT scans without intravenous contrast (n = 301) were retrospectively reviewed. Measurements of the angle of the vestibular aqueduct were made using the previously developed software tool. The tool could be applied to measure the vestibular aqueduct angle in most CT scans of the temporal bones (n = 572 ears, 95%). While the majority of ears fell within the normal range of <120 degrees (n = 462, 80%), fourteen ears (2.3%) in 13 patients were found to have vestibular aqueduct angles that meet criteria for hypoplastic MD (>140 degrees). Only one of the 13 patients had a diagnosis of MD and not in the ear in the hypoplastic category. An inconsistent pattern of other otologic diagnoses were found among the 13 individuals meeting criteria for hypoplastic MD. Although prior reports indicate the software has prognostic value in individuals with MD, these results suggest that the software may have lower positive predictive value when applied to a large population of individuals with varied otologic diagnoses.

Vestibular Aqueduct Morphology Correlates With Endolymphatic Sac Pathologies in Menière's Disease-A Correlative Histology and Computed Tomography Study

Hypothesis:

The vestibular aqueduct (VA) in Menière's disease (MD) exhibits different angular trajectories depending on the presenting endolymphatic sac (ES) pathology, i.e., 1) ES hypoplasia or 2) ES degeneration.

Background:

Hypoplasia or degeneration of the ES was consistently found in inner ears affected by MD. The two etiologically distinct ES pathologies presumably represent two disease “endotypes,” which may be associated with different clinical traits (“phenotypes”) of MD. Recognizing these endotypes in the clinical setting requires a diagnostic tool.

Methods:

1) Defining the angular trajectory of the VA (ATVA) in the axial plane. 2) Measuring age-dependent normative data for the ATVA in postmortem temporal bone histology material from normal adults and fetuses. 3) Validating ATVA measurements from normative CT imaging data. 4) Correlating the ATVA with different ES pathologies in histological materials and CT imaging data from MD patients.

Results:

1) The ATVA differed significantly between normal adults and MD cases with ES degeneration, as well as between fetuses and MD cases with ES hypoplasia; 2) a strong correlation between ATVA measurements in histological sections and CT imaging data was found; 3) a correlation between the ATVA, in particular its axial trajectory in the opercular region (angle α_exit), with degenerative (α_exit < 120°) and hypoplastic ES pathology (α_exit > 140°) was demonstrated.

Conclusion:

We established the ATVA as a radiographic surrogate marker for ES pathologies. CT-imaging-based determination of the ATVA enables endotyping of MD patients according to ES pathology. Future studies will apply this method to investigate whether ES endotypes distinguish clinically meaningful subgroups of MD patients.

[Large endolymphatic duct and sac syndrome (LEDS) : part I: analysis of imaging findings]

OBJECTIVE

Large endolymphatic duct and sac (LEDS) syndrome is the most common radiologically detectable form of inner ear malformation (IEM) associated with sensorineural hearing loss (SNHL). Nevertheless, it is relatively unknown in the German-speaking countries.

METHODS

Among all patients referred from ear, nose, and throat specialists to the radiology department with clinically suspected IEM between 1994 and 2003, we identified the cases of LEDS. The retrospective study included clinical records, high-resolution computed tomography, and magnetic resonance imaging.

RESULTS

Of 169 patients, 17 (median age 12 years; 12 females) showed LEDS. A total of 28 ears were affected. Ten patients (6%; 15 ears) had isolated LEDS, while seven patients showed additional IEM (4%; 13 ears). The most frequent of these was dysplastic vestibule (13/13 ears), followed by Mondini deformity (10/13 ears) and dilated semicircular canals (7/13 ears). Three of 13 ears revealed severe IEM of the cochlea, vestibule, and semicircular canals. No correlation could be demonstrated between the severity of morphological changes and the degree of SNHL.

CONCLUSION

LEDS may be an underestimated cause of SNHL. Imaging is necessary for a confident diagnosis.

An approach for precise three-dimensional modeling of the human inner ear

For further morphological and physiological research, it is vital to establish precise three-dimensional models of the whole inner ear including the details of the membranous components. With the system of a projector and a high-resolution digital camera, 2 complete serial unstained celloidin sections of fresh human temporal bones were digitized as high-resolution images which were then sorted, calibrated, aligned and segmented using the 3D-Doctor software. Finally, 2 precise three-dimensional models of the inner ear were generated by simple surface rendering. The contours of tiny structures such as the crista ampullaris, the macula utriculi and the macula sacculi could be observed clearly. Our study suggests that it is technically feasible to employ complete serial unstained celloidin sections for precise three-dimensional reconstruction and that this helps reduce errors and laboratory workload. Moreover, the use of a high-resolution digital camera and the autoalignment function of 3D-Doctor further increase the accuracy of the models.

Large vestibular aqueduct syndrome: audiological, radiological, clinical, and genetic features

PURPOSE

The aim of this study was to analyze the clinical, audiological, radiological, and genetic features of a group of patients affected with large vestibular aqueduct syndrome.

MATERIALS AND METHODS

Seventeen patients affected with large vestibular aqueduct syndrome (LVAS), diagnosed by means of high-resolution magnetic resonance imaging of the inner ear, with 3-dimensional reconstructions of the labyrinth and by high-resolution spiral computed tomography of the temporal bone, performed only on the oldest patients, have been submitted to a complete audiological evaluation, a thyroid functional and ultrasonographic study, and a molecular study of the PDS gene.

RESULTS

The clinical presentation of LVAS was very variable in our group of patients. The enlarged vestibular aqueduct was bilateral in 15 cases and unilateral in 2; it was the only malformation of the labyrinth in 12 patients, whereas it was associated with other inner ear anomalies in the other 5. The hearing loss was very variable in degree (from mild to profound), age at onset, and progression. Moreover, among the 17 patients, 10 were clinically affected by Pendred's syndrome (PS), 3 by distal renal tubular acidosis associated with large vestibular aqueduct, whereas in 3 patients the large vestibular aqueduct was not syndromal. Finally, we identified mutations in the PDS gene in 5 of 10 patients with PS.

CONCLUSIONS

Our data underscore the frequent role of the large vestibular aqueduct syndrome in the pathogenesis of sensorineural hearing loss and the overall wide variability in its audiological features. It is also highlighted that LVAS is often part of some syndromal diseases, most of which are PS, which is often misdiagnosed because of the varying degree of thyroid symptoms. This study also underscores the possible role of hydro-electrolyte and acid-base endolymphatic fluid disorders in the pathogenesis of enlarged vestibular aqueduct syndrome.

3-D reconstruction of the vestibular endorgans in pediatric temporal bones

We investigated the vestibular endorgans in three children using 3-D reconstructions from histological sections. The right temporal bone of a newborn child without peripheral vestibular pathology was used as reference model and the temporal bones from a child with Goldenhar syndrome and a child with Pierre Robin sequence with known peripheral vestibular pathology were studied. All five temporal bones were prepared by the celloidin technique and sectioned at 20 microm. Each available section was digitized with a slide scanner. The imaging data were layered anatomically correctly and rendered in a 3-D software. With this technique all vestibular endorgans were reconstructed and measured. The standard deviations in distances ranged between 0.5 and 1.2% and in angles between 0.1 and 2.9 degrees. Both maculae were curved in the longitudinal and transverse axes which described a curve of approximately 35 degrees. The angles between the semicircular ducts varied between 97 and 110 degrees. The pathological models demonstrated a distorted configuration of the semicircular canals and differed substantially from the reference model in most of the measured distances and angles. The method presented is capable of generating 3-D models of the vestibular system from histological sections with an acceptable precision without previously inserted reference marks. Archival celloidin sections are widely available and will be an important resource in understanding the detailed 3-D geometry of the vestibular system which has not yet been accomplished.

Malformation of stapes in VACTERLS association: a histopathologic study and three-dimensional reconstruction

OBJECTIVE

To investigate the temporal bone with a malformed stapes in VACTERLS association.

STUDY DESIGN

The study design was a case report, histopathology of the temporal bone, and three-dimensional reconstruction of the ossicles and cochlea.

SETTING

The study was carried out in the Temporal Bone Bank at Charles University, Hradec Králové, on a case from Temporal Bone Foundation, Boston.

PATIENT

A 1540-g, 41-cm female neonate with VACTERLS association, histopathology of the temporal bone, and three-dimensional reconstruction of the middle ear ossicles and cochlea.

RESULTS

The posterior part of the footplate was missing, and the posterior crura of the stapes was not connected to the footplate but found freely suspended in the sinus tympani.

CONCLUSION

Computer-assisted three-dimensional reconstruction was performed from histologic sections of the temporal bone removed from a case of VACTERLS association. The reconstruction included structures such as the bony labyrinth and the middle ear ossicles. The abnormality observed in the reconstruction included the mislocation of the stapes and a shortened footplate.