Optimizing CT for the evaluation of vestibular aqueduct enlargement: Inter-rater reproducibility and predictive value of reformatted CT measurements

"Transcanal view" computed tomography reformat: Applications for transcanal endoscopic ear surgery

PURPOSE

Transcanal endoscopic ear surgery (TEES) is an increasingly used surgical approach for otologic surgeries, but no en face preoperative imaging format currently exists. We aim to assess the utility of a transcanal high resolution computed tomography (HRCT) reformat suitable for TEES preoperative planning.

MATERIALS AND METHODS

Preoperative HRCTs of patients with middle ear pathologies (cholesteatoma, otosclerosis, and glomus tympanicum) who underwent TEES were obtained. Axial image series were rotated and reformatted -90 or +90 degrees for left and right ear surgeries, respectively, where additional rotation along the left-right axis was performed to align the transcanal series with the plane of the external auditory canal. Quantitative measurements of middle ear structures were recorded. Consecutive transcanal reformatted sections were then reviewed to identify critical middle ear anatomy and pathology with corresponding TEES cases.

RESULTS

The aforementioned methodology was used to create three transcanal view HRCTs. The mean left-right axis degree of rotation was 4.0 ± 2.2 degrees. In the cholesteatoma transcanal HRCT, areas of cholesteatoma involvement in middle ear compartments (e.g. epitympanum) and eroded ossicles were successfully identified in the corresponding case. In the otosclerosis transcanal HRCT, areas for potential otosclerotic involvement were visualized such as the round window as well as a low-hanging facial nerve. In the glomus tympanicum transcanal HRCT, the span of the glomus tympanicum was successfully visualized in addition to a high riding jugular bulb.

CONCLUSION

A transcanal HRCT reformat may aid preoperative planning for middle ear pathologies. This novel reformat may help highlight patient-specific anatomy.

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.

Increased diagnosis of enlarged vestibular aqueduct by multiplex PCR enrichment and next-generation sequencing of the SLC26A4 gene

Background

The enlarged vestibular aqueduct (EVA) is the commonest malformation of inner ear accompanied by sensorineural hearing loss in children. Three genes SLC26A4, FOXI1, and KCNJ10 have been associated with EVA, among them SLC26A4 being the most common. Yet, hotspot mutation screening can only diagnose a small number of patients.

Methods

Thus, in this study, we designed a new molecular diagnosis panel for EVA based on multiplex PCR enrichment and next‐generation sequencing of the exon and flanking regions of SLC26A4. A total of 112 hearing loss families with EVA were enrolled and the pathogenicity of the rare variants detected was interpreted according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

Results

Our results showed that 107/112 (95.54%) families carried SLC26A4 biallelic mutations, 4/112 (3.57%) carried monoallelic variants, and 1/112 (0.89%) had none variant, resulting in a diagnostic rate of 95.54%. A total of 49 different variants were detected in those patients and we classified 30 rare variants as pathogenic/likely pathogenic, of which 13 were not included in the Clinvar database.

Conclusion

Our diagnostic panel has an increased diagnostic yield with less cost, and the curated list of pathogenic variants in the SLC26A4 gene can be directly used to aid the genetic counseling to patients.

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.

Value of CT and three-dimensional reconstruction revealing specific radiological signs for screening causative high jugular bulb in patients with Meniere's disease

Background

The aim of the present study was to investigate the pathological features of vestibular aqueduct (VA) related high jugular bulb (HJB) and explore the possible cause-consequence relation between HJB and endolymphatic hydrops (EH), and the potential specific radiological signs for screening causative HJB in Meniere’s disease (MD).

Methods

High-resolution computed tomography (HRCT) and three-dimensional reconstruction (3DRC) were used to detect the anatomical variables associated with VA and jugular bulb (JB) in hydropic and non-hydropic ears. The presence or absence of EH in the inner ear was determined by gadopentetate dimeglumine-enhanced magnetic resonance imaging. The presence of different types of HJB, the anatomical variables of the VA and JB and the three types of anatomical relationship between the VA and HJB were compared between the hydropic and non-hydropic ears using the χ² or Fisher’s exact tests. P < 0.05 was considered to indicate a statistically significant difference.

Results

JB was classified as: Type 1, no bulb; type 2, below the inferior margin of the posterior semicircular canal (PSCC); type 3, between the inferior margin of the PSCC and the inferior margin of the internal auditory canal (IAC); type 4, above the inferior margin of the IAC. There were no significant differences in the presence of types 1, 2 and 3 JB between two groups. The presence of type 4 JB, average height of the JB and prevalence of the non-visualization of the VA in CT scans showed significant differences between two groups. The morphological pattern between the JB and VA revealing by 3DRC was classified as: Type I, the JB was not in contact with the VA; type II, the JB was in contact with the VA, but the latter was intact without obstruction; type III, the VA was obliterated by HJB encroachment. There were no significant differences in the presence of type I and II between two groups. Type III was identified in 5 hydropic ears but no non-hydropic ears, with a significant difference observed between the two groups.

Conclusion

The present results showed that JB height and non-visualization of the VA on Pöschl’s plane could render patients susceptible to the development of EH. A jugular bulb reaching above the inferior margin of the IAC (type 4 JB) could obstruct VA, resulting in EH in a few isolated patients with MD. VA obliteration revealed by 3DRC, as a specific radiological sign, may have the potential for screening causative HJB in MD.

Radiological diagnosis of the inner ear malformations in children with sensorineural hearing loss

Malformations in either the inner ear, vestibulocochlear nerve (VIIIth) or auditory cortex of the brain can lead to congenital sensorineural hearing loss (SNHL). In most cases the underlying disorders involve the membranous labyrinth at a microscopic level and therefore radiological examinations are entirely normal. In a significant proportion however (up to 20%), there are abnormalities visualized in the inner ear and/or the VIIIth nerve; the type of abnormality is relevant for the surgical planning of a cochlear implant. Imaging and the accurate radiological identification of the affected inner ear structures therefore plays an integral role in the clinical evaluation of sensorineural hearing loss. In this pictorial review, we describe the main malformations of the inner ear in view of recent classifications and briefly explore the surgical implications.

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.