Comparison of 45 degrees oblique reformats with axial reformats in CT evaluation of the vestibular aqueduct

Novel and pragmatic exploration of variation in glottic parameters in non-parallel versus parallel vocal cord CT planes with potential reporting pitfalls

Oblique orientation of vocal cord demands strict compliance, by technicians and clinicians, to the recommended parallel plane CT scan of larynx. Repercussions of non-compliance has never been investigated before. We aimed to observe influence of non-parallel vocal cord plane CT scan on qualitative and quantitative glottic parameters, keeping parallel plane CT as a standard for comparison. Simultaneous identification of potential suboptimal imaging sequelae as a result of unformatted CT plane was also identified. In this study we included 95 normal adult glottides and retrospectively analyzed their anatomy in two axial planes, non-parallel plane ① and parallel to vocal cord plane ②. Qualitative (shape, structures at glottic level) and quantitative (anterior commissure ACom, vocal cord width VCw, anteroposterior AP, transverse Tr, cross-sectional area CSA) glottic variables were recorded. Multivariate statistical analysis was used to predict pattern and their impact on glottic anatomy. Plane ① displayed supraglottic features in glottis; adipose (90.5%) and split thyroid laminae (70.6%). Other categorical variables: atypical shape, submental structures and multilevel vertebral crossing were also in majority. All glottic dimensions varied significantly between two planes with most in ACom (-5.8mm) and CSA (-15.0 mm2). In contrast, plane ② manifested higher VCw (>73%), Tr (66.3%), CSA (64.2%) and AP (44.2%) measurements. On correlation analysis, variation in ACom, CSA, Tr was positively associated with VC or plane obliquity (p<0.05). This variability was more in obese and short necked subjects. Change in one parameter also modified other significantly i.e., ACom versus AP and CSA versus Tr. Results indicated statistically significant change in subjective and objective anatomical parameters of glottis on non-application of appropriate CT larynx protocol for image analysis hence highlighting importance of image reformation.

Analysis of the vestibular aqueduct development on the risk for suffering from idiopathic sudden sensorineural hearing loss

OBJECTIVE

Large vestibular aqueduct syndrome (LVAS) is one of the etiology of hearing loss. Clinically, we observed that the VA size of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) did not meet the diagnostic criteria of VA enlargement, but there were individual variations. Through this study, we want to understand the VA development and explore its risk for suffering from ISSNHL.

METHODS

74 patients with ISSNHL were retrospectively reviewed in our department from June 2018 to September 2021. Meanwhile, 57 people with no ear diseases were randomly selected as the control group. All their clinical information were systematically collected. The axial thin-slice CT images of temporal bone were used to observe and measure the VA in ISSNHL and controls. ISSNHL were classified as different types and grades according to pure tone audiometry and the degree of hearing loss, respectively. Logistic regression analysis was adopted to evaluate the risk factors of different types and grades of ISSNHL.

RESULTS

The operculum morphology could be funnel-shaped, tubular and invisible, but they had no statistical difference in the morbidity of ISSNHL. The operculum width of the affected sides in the case group was significantly wider than that of the matched sides in the control group (0.84±0.35mm vs 0.68±0.34mm, p=0.009), but the midpoint width had no statistical difference (p=0.447). The operculum width was an independent risk factor for the total hearing loss type (p=0.036, OR=4.49, 95% CI=1.10-18.29), moderate (p=0.013, OR=17.62, 95% CI=1.82-170.95) and profound (p=0.031, OR=4.50, 95% CI=1.14-17.67) grade of ISSNHL. Hypertension was an independent risk factor for the severe grade (p=0.004, OR=12.44, 95% CI=2.19-70.64) of ISSNHL. Both the operculum width (p=0.048, OR=7.14, 95% CI=1.02-50.26) and hypertension (p=0.014, OR=6.73, 95% CI=1.46-30.97) were the risk factors for the flat type of ISSNHL. The midpoint width of the VA, gender, age, diabetes mellitus, hyperlipidemia, and plasma fibrinogen concentration had no significant effect on the risk for suffering from ISSNHL.

CONCLUSION

The development of the VA operculum is a risk factor for some types and grades of ISSNHL. Hypertension remained a risk factor for ISSNHL.

Classifying the Large Vestibular Aqueduct: Morphometry to Audiometry

OBJECTIVE

Large vestibular aqueduct (LVA) is the most common inner ear dysplasia identified in patients with hearing loss. Our objective was to systematically quantify LVA morphologies and correlate imaging findings with established audiometric outcomes.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

PATIENTS

Patients with large vestibular aqueduct identified radiographically, with or without hearing loss.

INTERVENTIONS

Diagnostic only.

MAIN OUTCOME MEASURES

Vestibular aqueduct (VA) width at midpoint, width at external aperture, and length were measured on cross-sectional imaging. Morphology was classified as type I (borderline), type II (tubular), or type III (funneled). Audiometric endpoints included air/bone conduction, pure tone averages, and air-bone gaps at 250 and 500 Hz. Statistical associations were evaluated using linear regression models, adjusted for age at first audiogram and sex.

RESULTS

One hundred seventeen patients (197 ears) were included, with mean age at first audiogram of 22.2 years (standard deviation, 21.7 yr). Imaging features associated with poor audiometric outcomes were increasing VA width at midpoint and external aperture, decreasing VA length, dilated extraosseous endolymphatic sac, cochleovestibular malformations, and increasing VA type (III > II > I).

CONCLUSIONS

Quantitative LVA measurements and a standardized morphologic classification system aid in prediction of early audiometric endpoints.

Retrospective Review of Midpoint Vestibular Aqueduct Size in the 45° Oblique (Pöschl) Plane and Correlation with Hearing Loss in Patients with Enlarged Vestibular Aqueduct

BACKGROUND AND PURPOSE

Vestibular aqueduct measurements in the 45° oblique (Pöschl) plane provide a reliable depiction of the vestibular aqueduct; however, adoption among clinicians attempting to counsel patients has been limited due to the lack of correlation with audiologic measures. This study aimed to determine the correlation between midpoint vestibular aqueduct measurements in the Pöschl plane in patients with an enlarged vestibular aqueduct with repeat audiologic measures.

MATERIALS AND METHODS

Two radiologists independently measured the midpoint vestibular aqueduct diameter in the Pöschl plane reformatted from CT images in 54 pediatric patients (77 ears; mean age at first audiogram, 5 years) with an enlarged vestibular aqueduct. Four hundred nineteen audiograms were reviewed, with a median of 6 audiograms per patient (range, 3-17; mean time between first and last audiograms, 97.4 months). The correlation between midpoint vestibular aqueduct size and repeat audiologic measures (pure tone average, speech-reception threshold, and word recognition score) using a linear mixed-effects model was determined.

RESULTS

The mean midpoint vestibular aqueduct size was 1.78 mm (range, 0.81-3.46 mm). There was excellent interobserver reliability with intraclass correlation coefficients for the 2 readers measuring 0.92 (P < .001). Each millimeter increase in vestibular aqueduct size was associated with an increase of 10.5 dB (P = .006) in the pure tone average, an increase of 14.0 dB (P = .002) in the speech-reception threshold, and a decrease in the word recognition score by 10.5% (P = .05).

CONCLUSIONS

Midpoint vestibular aqueduct measurements in the Pöschl plane are highly reproducible and demonstrate a significant correlation with audiologic data in this longitudinal study with repeat measures. These data may be helpful for clinicians who are counseling patients with an enlarged vestibular aqueduct using measurements obtained in the Pöschl plane.

New Navigation Approaches for Endoscopic Lateral Skull Base Surgery

Image-guided navigation is well established for surgery of the brain and anterior skull base. Although navigation workstations have been used widely by neurosurgeons and rhinologists for decades, utilization in the lateral skull base (LSB) has been less due to stricter requirements for overall accuracy less than 1 mm in this region. Endoscopic approaches to the LSB facilitate minimally invasive surgeries with less morbidity, yet there are risks of injury to critical structures. With improvements in technology over the years, image-guided navigation for endoscopic LSB surgery can reduce operative time, optimize exposure for surgical corridors, and increase safety in difficult cases.

Conductive hearing loss in large vestibular aqueduct syndrome -clinical observations and proof-of-concept predictive modeling by a biomechanical approach

OBJECTIVE

The purpose of this study was to investigate the effect of a dilated vestibular aqueduct on conductive hearing loss (CHL). A biomechanical method was proposed for modeling the patterns of CHL in patients with large vestibular aqueduct syndrome (LVAS).

STUDY DESIGN

High resolution computed tomography (CT) scans and pure tone audiometry (PTA) were retrospectively collected from 16 patients who were diagnosed with LVAS. Seventeen ears with measurable air-bone gaps (ABGs) on PTA were applied for model development. The sizes of midpoint, operculum and distal segment were measured from CT to calculate the biomechanical parameters of each vestibular aqueduct. The mechanical effect of the dilated vestibular aqueduct on sound conduction was simulated using a lumped-parameter model. The CHL levels predicted by the model were compared with the observed ABGs at 250, 500 and 1000 Hz respectively.

RESULTS

The model was able to predict the trend that greater ABGs occurred at lower frequencies, which were consistent with clinical observations. However, deviations between the predicted and the observed ABGs became larger as the frequency increased. None of the correlation coefficients between the radiologic measures and the observed ABG levels were significant.

CONCLUSION

These findings lend support to the feasibility of this approach in modeling CHL in LVAS. The presence of a dilated vestibular aqueduct leads to altered impedance and sound pressure, suggesting the impact of a pathological third window. High individual variability of the observed ABGs implies additional factors may also be involved, especially at 500 Hz and 1000 Hz.

Auditory and imaging markers of atypical enlarged vestibular aqueduct

PURPOSE

To characterize the auditory and imaging markers of atypical enlarged vestibular aqueduct (EVA).

METHODS

15 EVA cases (26 ears) confirmed via high-resolution MRI (HRMRI) that did not meet the Valvassori criterion on high-resolution CT (HRCT) were classified as atypical EVA. Another 21 EVA cases (40 ears) meeting the Valvassori criterion were randomly chosen as typical EVA. The hearing loss (HL), HRCT, and HRMRI findings were compared between the two groups.

RESULTS

The difference of HL severity between atypical and typical EVA was not statistically significant (χ² = 0.12, P > 0.05. The vestibular aqueducts (VA) of atypical EVA cases manifested as borderline dilation (n = 17), focal dilation (n = 3), and normal appearance (n = 6) on the HRCT. The midpoint width of atypical and typical EVA cases was 1.06 ± 0.18 mm and 2.10 ± 0.55 mm, respectively, exhibiting a significant difference (t = - 9.20, P < 0.05). In the HRMRI, the degree of dilation and shape of the intraosseous partition of endolymphatic duct and sac (ES) was similar to that of VA on HRCT, while their extraosseous ES was depicted variable slighter dilation compared to that of typical one, the difference between them was statistically significant (t = - 4.10, P < 0.05).

CONCLUSION

The HL severity of atypical EVA ears was similar to that of typical ones. Nevertheless, borderline, focal dilation and normal-like appearance of VAs on HRCT and variablely slighter dilation of the extraosseous ES on HRMRI are its characteristic imaging findings.

The Diagnostic Efficacy of MRI in the Evaluation of the Enlarged Vestibular Aqueduct in Children with Hearing Loss

Objective

The aim of our study is to evaluate the diagnostic effectiveness of magnetic resonance imaging (MRI) compared to computed tomography (CT) in the detection of enlarged vestibular aqueduct (EVA) in childhood.

Methods

One hundred twenty-three children who underwent temporal bone CT and MRI examinations for hearing loss between 2013 and 2020 were evaluated retrospectively. All CT and MRI images were examined by two pediatric radiologists, according to the Valvassori and Cincinnati criteria for EVA. Imaging findings on CT and MRI of the vestibular aqueduct were recorded. Two pediatric radiologists performed the measurements for EVA on CT and MRI. In addition, an otolaryngologist performed the measurements independently. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRI compared to CT were calculated to detect EVA. The difference between the measurements on CT and MRI was investigated. The inter-observer agreement was evaluated for measurements.

Results

The mean age of 123 children (65 boys and 58 girls) was 50.18±50.40 months. Two hundred forty-six ears were evaluated in 123 children. On CT images, EVA was present in 28 (11.3%) of 246 ears according to Cincinnati criteria and 27 (10.9%) of 246 ears according to Valvassori criteria, respectively. While sensitivity, specificity, PPD, and NPD rates of MRI were 100%, 99%, 92.8%, and 100%, respectively, for Cincinnati criteria, for Valvassori criteria, they were 100%, 97.3%, 77.7%, and 100%, respectively. According to the visual evaluation performed without using measurement, the enlarged appearance of the vestibular aqueduct was significant for the diagnosis of EVA (p<0.001), while the absence of this appearance was significant for the exclusion of EVA (p<0.001). There was no significant difference between the measurements on CT and MRI. There was a perfect correlation between the observers for measurements.

Conclusion

MRI can be used as an initial imaging technique in children with suspicion of EVA to reduce radiation exposure.

Imaging in congenital inner ear malformations-An algorithmic approach

Malformations of the inner ear are an important cause of congenital deaf-mutism. Arrest in embryologic development of inner ear during various stages gives rise to the variety of malformations encountered. Current treatment options include hearing aids, cochlear implants, and auditory brainstem implants (ABI). With the advent of cochlear implant surgery and ABI, decent functional outcomes can be obtained provided such cases are diagnosed correctly and timely. To that end, high-resolution computed tomography (HRCT) has a fundamental role in the assessment of these conditions, ably supplemented by magnetic resonance imaging (MRI). The purpose of this pictorial essay is to illustrate the imaging features of inner ear anomalies in children with congenital deaf-mutism as per the latest terminology and classification and provide an algorithmic approach for their diagnosis.

Microtomographic morphometry of the stapedius muscle and its tendon

The aim of this study was to evaluate the morphology of the stapedius muscle and its tendon with the use of microCT and to describe their anatomic relationship with facial nerve and incudostapedial joint. The study was performed on 16 fresh cadaveric temporal bones scanned in microtomography (microCT). Stapedius muscle and its tendon were identified in each set of images. The length of the medial and lateral border of the stapedius tendon (STL-med, STL-lat), width at the insertion to stapes (STW-s), at the point it emerges from the pyramidal eminence (STW-p) and in the half way from the pyramidal eminence to stapes (STW-m), and the length and the width of the belly of stapedius muscle (BSML and BSMW) were measured in modified axial plane. The shortest distance between the facial canal and incudostapedial joint (FN-isj), and between the facial canal and stapedius tendon (FN-st) were measured in the Pöschl plane. The average values of all distances measured were: STL-lat 1.29 ± 0.50 mm, STL-med 1.27 ± 0.44 mm, BSML 2.98 ± 0.51 mm, STW-s 0.47 ± 0.10 mm, STW-p 0.46 ± 0.12 mm, STW-m 0.35 ± 0.12 mm, BSMW 1.26 ± 0.29 mm, FN-isj 1.72 ± 0.33 mm, FN-st 1.35 ± 0.30 mm. The stapedius muscle complex consists of the tendon and the belly, and the border between them in microCT scans is not always evident. The distance between the facial nerve and the incudostapedial joint is greater than the distance between the facial nerve and the stapedius muscle tendon.

Variability of vestibular aqueduct measurements among axial, single-oblique and double-oblique computed tomography images

OBJECTIVE

To investigate the morphology and dimensions of the vestibular aqueduct on axial, single-oblique and double-oblique computed tomography images.

METHODS

The computed tomography temporal bone scans of 112 patients were retrospectively evaluated. Midpoint and opercular measurements were performed using axial, single-oblique and double-oblique images. Morphometric analyses were also conducted. The vestibular aqueduct sizes on axial, single-oblique and double-oblique images were compared.

RESULTS

At the midpoint, the mean (± standard deviation) vestibular aqueduct measured 0.61 ± 0.23 mm, 0.74 ± 0.27 mm and 0.82 ± 0.38 mm on axial, single-oblique and double-oblique images, respectively; at the operculum, the vestibular aqueduct measured 0.91 ± 0.30 mm, 1.11 ± 0.45 mm and 1.66 ± 1.07 mm on the respective images. The co-efficients of variation of the vestibular aqueduct measured at the midpoint were 37.4 per cent, 36.5 per cent and 47.5 per cent on axial, single-oblique and double-oblique images, respectively; at the operculum, the measurements were 33.0 per cent, 40.5 per cent and 64.5 per cent. Regarding morphology, the vestibular aqueduct was fissured (33.5 per cent), tubular (64.3 per cent) or invisible (2.2 per cent).

CONCLUSION

The morphology and dimensions of the vestibular aqueduct were highly variable among axial, single-oblique and double-oblique images.

An Investigation of the Morphology of the Petrotympanic Fissure Using Cone-Beam Computed Tomography

Objectives

The purpose of the present study was: a) to examine the visibility and morphology of the petrotympanic fissure on cone-beam computed tomography images, and b) to investigate whether the petrotympanic fissure morphology is significantly affected by gender and age, or not.

Material and Methods

Using Newtom VGi (QR Verona, Italy), 106 cone-beam computed tomography examinations (212 temporomandibular joint areas) of both genders were retrospectively and randomly selected. Two observers examined the images and subsequently classified by consensus the petrotympanic fissure morphology into the following three types: type 1 - widely open; type 2 - narrow middle; type 3 - very narrow/closed.

Results

The petrotympanic fissure morphology was assessed as type 1, type 2, and type 3 in 85 (40.1%), 72 (34.0%), and 55 (25.9%) cases, respectively. No significant difference was found between left and right petrotympanic fissure morphology (Kappa = 0.37; P < 0.001). Furthermore, no significant difference was found between genders, specifically P = 0.264 and P = 0.211 for the right and left petrotympanic fissure morphology, respectively. However, the ordinal logistic regression analysis showed that males tend to have narrower petrotympanic fissures, in particular OR = 1.58 for right and OR = 1.5 for left petrotympanic fissure.

Conclusions

The current study lends support to the conclusion that an enhanced multi-planar cone-beam computed tomography yields a clear depiction of the petrotympanic fissure's morphological characteristics. We have found that the morphology is neither gender nor age-related.

The Human Vestibular Aqueduct: Anatomical Characteristics and Enlargement Criteria

HYPOTHESIS

The human vestibular aqueduct (VA) shows great anatomical variations, and imaging can be difficult, so we need more data on the normal anatomy of the VA for better radiologic evaluation of large vestibular aqueduct syndrome (LVAS).

BACKGROUND

The normal anatomy of the human VA was analyzed in micro-dissected human temporal bones.

METHODS

The study is based on two sets of human temporal bones. One set of 32 human temporal bones was selected from a collection of 50 micro-dissected specimens. The outline of the intraosseous portion of the VA was drawn and digitized, and dimensions were assessed. The other set of 20 plastic molds were randomly selected from a collection of 324 specimens, and the VA dimensions were assessed.

RESULTS

Measurements from this study are presented in means, standard deviations, and ranges. The results from these measurements are considered normal and compared with previously published data. The variations in the normal anatomy of the VA are presented and discussed.

CONCLUSION

The VA courses sagittal in the human skull. Therefore, we recommend the lateral projection (reformatted) to demonstrate the VA in LVAS patients. We advocate assessing: 1) the width (or height) of the external aperture (EA), 2) the width at the half distance between the EA and the common crus (CC), and if possible 3) the width of the proximal portion of the VA. Based on the measurements, our criteria for enlargement are 2.0 mm or greater, 1.5 mm or greater, and more than 1 mm at these sites.

Vestibular Aqueduct Measurements in the 45° Oblique (Pöschl) Plane

BACKGROUND AND PURPOSE

The 45° oblique (Pöschl) plane allows reliable depiction of the vestibular aqueduct, with virtually its entire length often visible on 1 CT image. We measured its midpoint width in this plane, aiming to determine normal measurement values based on this plane.

MATERIALS AND METHODS

We retrospectively evaluated temporal bone CT studies of 96 pediatric patients without sensorineural hearing loss. Midvestibular aqueduct widths were measured in the 45° oblique plane by 2 independent readers by visual assessment (subjective technique). The vestibular aqueducts in 4 human cadaver specimens were also measured in this plane. In addition, there was a specimen that had undergone CT scanning before sectioning, and measurements made on that CT scan and on the histologic section were compared. Measurements from the 96 patients' CT images were then repeated by using findings derived from the radiologic-histologic comparison (objective technique).

RESULTS

All vestibular aqueducts were clearly identifiable on 45° oblique-plane CT images. The mean for subjective measurement was 0.526 ± 0.08 mm (range, 0.337-0.947 mm). The 97.5th percentile value was 0.702 mm. The mean for objective measurement was 0.537 ± 0.077 mm (range, 0.331-0.922 mm). The 97.5th percentile value was 0.717 mm.

CONCLUSIONS

Measurements of the vestibular aqueduct can be performed reliably and accurately in the 45° oblique plane. The mean midpoint width was 0.5 mm, with a range of 0.3-0.9 mm. These may be considered normal measurement values for the vestibular aqueduct midpoint width when measured in the 45° oblique plane.

Evaluation of the radiological criteria to diagnose large vestibular aqueduct syndrome

OBJECTIVE

The main objective of the current work is to increase the sensitivity of the radiological diagnosis of the large vestibular aqueduct syndrome (LVAS). The specific aims were to compare between the two famous criteria to diagnose large vestibular aqueduct (LVA), (i.e., Valvassori and Cincinnati), to correlate between vestibular aqueduct (VA) measurements in the axial view and those in 45° oblique reformate in children with LVAS, and to define radiological criteria to diagnose LVA in the 45° oblique reformate.

METHODS

The study group included 61 children with LVAS according to Cincinnati criteria (greater than 0.9mm at the midpoint or greater than 1.9mm at the operculum in the axial view). All participants were subjected to full Audiological evaluation and CT scanning in axial plane. The axial data were then transferred to workstation for post-processing with 3D reformatting software (Baxara 3D) in order to obtain the 45° oblique reformates. VA measurements were done at 4 points: midpoint and operculum in both the axial plane and the 45° oblique reformate.

RESULTS

Only 81% of ears of children with LVAS (99 ears) fit Valvassori criterion (i.e., larger than 1.5mm at midpoint), while 19% (23 ears) of them were missed. There were statistically significant correlations among the diameters of the VA in the axial view (both in the midpoint and operculum) and their counterparts in the 45° oblique reformate. Values equal to or greater than 1.2mm in the midpoint and 1.3mm in the operculum are proposed to be the criteria to diagnose LVA in the 45° oblique reformate. Finally, no significant correlations were found between the degree of hearing loss and VA diameters at the axial or 45° oblique reformate.

CONCLUSION

Cincinnati criteria are more sensitive than Valvassori criterin in the diagnosis of LVAS. We recommend the application of Cincinnati criteria instead of Valvassori criteria in order not miss cases with LVAS. Measurement of VA in the 45° oblique reformate is a reliable method to diagnose LVA. Criteria to diagnose LVA in the 45° oblique reformate were proposed.

Curvature measurement of human bilateral cochleae

OBJECTIVE

This study aimed to characterise the geometry of the human bilateral spiral cochlea by measuring curvature and length.

METHOD

Eight subjects were recruited in this study. Magnetic resonance imaging was used to visualise the right and left cochlea. Visualisation of the cochlear spiral was enhanced by T2 weighting and further processing of the raw images. The spirals were divided into three segments: the basal turn, the middle turn and the apex turn. The length and curvature of each segment were non-invasively measured.

RESULTS

The mean left and right cochlear lengths were 3.11 cm and 3.95 cm, respectively. The measured lengths of the cochlear spiral are consistent with data in the literature derived from anatomical dissections. Overall, the apex turn segment of the cochlea had the greatest degree of curvature (p < 0.05). The mean apex turn segment curvatures for left and right cochleae were 9.65 cm(-1) and 10.09 cm(-1), respectively.

CONCLUSION

A detailed description of the cochlear spiral is provided, using measurements of curvature and length. These data will provide a valuable reference in the development of cochlear implantation procedures for minimising the potential damage during implantation.

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.

Dilated dysplastic vestibule: a new computed tomographic finding in patients with large vestibular aqueduct syndrome

OBJECTIVE

Large vestibular aqueduct syndrome (LVAS) is one of the most common anomalies of the inner ear. The purpose of our study was to evaluate the vestibule for associated aberrations. In particular, we assessed the vestibular volume in patients with LVAS, compared it to an age-matched control population, and evaluated the relationship between the size of the vestibular aqueduct and the vestibule.

METHODS

We reviewed studies of high-resolution computed tomography of temporal bone of 24 consecutive patients with LVAS (15 girls and 9 boys; average age, 8.1 years). Of these, 21 patients had bilateral LVAS and 3 patients had unilateral LVAS. Each ear was evaluated for the size of the vestibular aqueduct and the volume of the vestibule. Similar measurements were obtained in an age-matched control population (28 girls and 18 boys; average age, 8.3 years).

RESULTS

The volume of the vestibule was found to be significantly enlarged in patients with LVAS compared to the control population (right ear, P < 0.0001; left ear, P < 0.0001). A linear correlation could be established between an enlarged vestibular aqueduct and corresponding increase in the volume of the vestibule (right side, P < 0.01; left side, P < 0.01).

CONCLUSION

A dilated dysplastic vestibule is a consistently associated finding in patients with LVAS.

Superior semicircular canal dehiscence and enlarged vestibular aqueduct

Superior semicircular canal dehiscence is a well described labyrinthine defect, detect in pediatric population too. We report a case of superior semicircular canal dehiscence, which radiological diagnosis was confirmed by multiplanar reformatted CT images, associated to omolateral enlarged vestibular aqueduct in a 16-year-old female who presented with congenital hearing loss without vestibular symptoms. Both inner ear malformations act as a third mobile window into the labyrinth and cochleo-vestibular symptoms can result from loud sounds or pressure changes. An early diagnosis should be strived for preserve inner ear functions.