Imaging Studies in Otosclerosis: An Up-to-date Comprehensive Review

Histopathological Patterns of Otosclerosis Progression: Exploring Otic Capsule and Round Window Involvement

OBJECTIVES

Obliteration of the round window (RW) in cases of otosclerosis presents a significant clinical challenge due to its association with more severe hearing loss and a poorer prognosis for functional recovery after stapes surgery. The objective is to assess and characterize the occurrence of RW involvement in otosclerosis cases and to identify patterns of disease progression that may indicate a potential for RW obliteration.

METHODS

We selected archival temporal bones from donors with otosclerosis. We evaluated the degree of RW obliteration using a semi-quantitative scale and the location of the foci within the temporal bone, and whether the foci were continuous or isolated.

RESULTS

Most of the foci were located anteriorly to the oval window (89.2%), while RW area involvement was seen in 26.9% of the ears. In cases with fenestral foci, 68.1% directly involved and/or fixed the footplate. Among donors with bilateral otosclerosis, foci affected both ears in a similar pattern in 64.2%. Among donors with RW involvement, ones with continuous, large lesions that extended from the oval window associated with complete RW obliteration, while ones with smaller degrees of obliteration had solitary foci scattered within the otic capsule.

CONCLUSION

Our results demonstrate a high rate of RW involvement in cases of otosclerosis. Ears with continuous lesions extending from the oval window region to the RW area were more likely to present with complete RW obliteration. These results provide insights that could lead to better prognostic assessment of patients with otosclerosis in the future.

LEVEL OF EVIDENCE

NA Laryngoscope, 135:324-330, 2025.

Comparison Between the Veillon and the Symons-Fanning CT Classification Systems for Otosclerosis

OBJECTIVE

To analyze the correlation between outcomes of stapes surgery and preoperative and postoperative audiometric results with different radiological staging classifications such as the Veillon classification (VC) and the Symons-Fanning classification (SFC).

STUDY DESIGN

Retrospective observational study.

SETTING

One tertiary hospital center.

PATIENTS

Adult patients submitted to stapes surgery due to otosclerosis from January 2017 to December 2022.

INTERVENTION

Evaluation of different radiological classifications such as the VC and SFC.

MAIN OUTCOME MEASURES

Preoperative and postoperative pure-tone audiometric data, outcomes of stapes surgery success (closure of the ABG, rates of AC threshold less than or equal to 30 dB), and postoperative sensorineural hearing loss.

RESULTS

A total of 87 patients and 97 operated ears were included. The SFC was associated with preoperative BC (p = 0.041) and AC (p = 0.018) and postoperative BC (p = 0.026) with an increase in thresholds with higher radiological stages. The VC was associated with postoperative AC (p = 0.045) with an increase in AC thresholds with increasing radiological stages. Lastly, both the VC (p = 0.032) and the SFC (p = 0.023) were associated with a decrease in rates of postoperative AC thresholds ≤30 dB with higher radiological stages.

CONCLUSIONS

The SFC seems to be more useful to predict preoperative AC and BC and postoperative BC. On the contrary, the VC was more useful to predict postoperative AC. Both scales were similarly associated with the rate of AC thresholds ≤30 dB.

Training and validation of a deep learning U-net architecture general model for automated segmentation of inner ear from CT

BACKGROUND

The intricate three-dimensional anatomy of the inner ear presents significant challenges in diagnostic procedures and critical surgical interventions. Recent advancements in deep learning (DL), particularly convolutional neural networks (CNN), have shown promise for segmenting specific structures in medical imaging. This study aimed to train and externally validate an open-source U-net DL general model for automated segmentation of the inner ear from computed tomography (CT) scans, using quantitative and qualitative assessments.

METHODS

In this multicenter study, we retrospectively collected a dataset of 271 CT scans to train an open-source U-net CNN model. An external set of 70 CT scans was used to evaluate the performance of the trained model. The model's efficacy was quantitatively assessed using the Dice similarity coefficient (DSC) and qualitatively assessed using a 4-level Likert score. For comparative analysis, manual segmentation served as the reference standard, with assessments made on both training and validation datasets, as well as stratified analysis of normal and pathological subgroups.

RESULTS

The optimized model yielded a mean DSC of 0.83 and achieved a Likert score of 1 in 42% of the cases, in conjunction with a significantly reduced processing time. Nevertheless, 27% of the patients received an indeterminate Likert score of 4. Overall, the mean DSCs were notably higher in the validation dataset than in the training dataset.

CONCLUSION

This study supports the external validation of an open-source U-net model for the automated segmentation of the inner ear from CT scans.

RELEVANCE STATEMENT

This study optimized and assessed an open-source general deep learning model for automated segmentation of the inner ear using temporal CT scans, offering perspectives for application in clinical routine. The model weights, study datasets, and baseline model are worldwide accessible.

KEY POINTS

A general open-source deep learning model was trained for CT automated inner ear segmentation. The Dice similarity coefficient was 0.83 and a Likert score of 1 was attributed to 42% of automated segmentations. The influence of scanning protocols on the model performances remains to be assessed.

Measurement of stapes footplate thickness using ultra-high-resolution computed tomography: stapes axial plane correlates better with otosclerosis than lateral semicircular canal plane

BACKGROUND, AIMS

Stapes footplate thickness measurement using ultra-high-resolution CT has been described only in the lateral semicircular canal plane. The purpose of this study was to compare stapes footplate thickness between the lateral semicircular canal and stapes axial planes in patients with otosclerosis compared to controls.

MATERIAL AND METHODS

We performed a retrospective single-center study of patients undergoing high-resolution temporal bone CT. Two radiologists measured stapes footplate thickness in both the lateral semicircular canal and stapes axial planes.

RESULTS

Between February 2020 and October 2022, we collected 81 ears from 49 patients (75% of women; mean age 51.22 ± 16.6 years, 17 otosclerosis, and 64 controls). In the stapes axial plane, there was a significant anterior thickening in otosclerosis patients (Reader 1: 0.52 ± 0.12 [0.3-0.7] vs. 0.41 ± 0.08 [0.3-0.6], p = 0.001; Reader 2: 0.54 ± 0.06 [0.5-0.7] vs. 0.39 ± 0.08 [0.2-0.6], P < 0.001) compared to controls. These differences were not significant using the lateral semicircular canal plane.

CONCLUSION

The stapes footplate was thickened at its AC in otosclerosis patients using only the stapes axial plane.

SIGNIFICANCE

We propose to use the stapes axial plane instead of the lateral semicircular canal plane when analyzing the stapes.

Temporal Bone High Resolution Computed Tomography Findings in a Case of Postpartum Otosclerosis

We describe temporal bone high resolution computed tomography (HRCT) findings in a case of bilateral mixed fenestral and retrofenestral otosclerosis with onset in the postpartum period. This condition should be considered in women complaining of postpartum hearing loss and temporal bone HRCT is a fundamental tool leading to the diagnosis.

Comparative study of the sensitivity of ultra-high-resolution CT and high-resolution CT in the diagnosis of isolated fenestral otosclerosis

PURPOSE

To compare the diagnostic sensitivity of ultra-high-resolution computed tomography (U-HRCT) and HRCT in isolated fenestral otosclerosis (IFO).

METHODS

A retrospective analysis was conducted on 85 patients (85 ears) diagnosed with IFO between October 2020 and November 2022. U-HRCT (0.1 mm thickness) was performed for 20 ears, HRCT (0.67 mm thickness) for 45 ears, and both for 20 ears. The images were evaluated by general radiologists and neuroradiologists who were blinded to the diagnosis and surgical information. The diagnostic sensitivity of U-HRCT and HRCT for detecting IFO was compared between the two groups.

RESULTS

Excellent inter-observer agreement existed between the two neuroradiologists (Cohen's κ coefficient 0.806, 95% CI 0.692-0.920), with good agreement between the general radiologists (Cohen's κ coefficient 0.680, 95% CI 0.417-0.943). U-HRCT had a sensitivity of 100% (40/40 ears) for neuroradiologists and 87.5% (35/40 ears) for general radiologists, significantly higher than HRCT (89.2% [58/65 ears] for neuroradiologists; 41.5% [27/65 ears] for general radiologists) (p = 0.042, p' < 0.000). General radiologists' sensitivity with HRCT was significantly lower compared to neuroradiologists (p < 0.000), but no significant difference was observed when general radiologists switched to U-HRCT (p = 0.152). Among the 20 ears that underwent both examinations, U-HRCT detected lesions smaller than 1 mm in 5 ears, whereas HRCT's sensitivity for neuroradiologists was 40% (2/5 ears), significantly lower than for lesions larger than 1 mm (93.3%, 14/15 ears, p = 0.032).

CONCLUSION

U-HRCT exhibits higher sensitivity than HRCT in diagnosing IFO, suggesting its potential as a screening tool for suspected otosclerosis patients.

CRITICAL RELEVANCE STATEMENT

Ultra-high-resolution computed tomography has the potential to become a screening tool in patients with suspected otosclerosis and to bridge the diagnostic accuracy gap between general radiologists and neuroradiologists.

KEY POINTS

• U-HRCT exhibits higher sensitivity than HRCT in the diagnosis of IFO. • U-HRCT has a significant advantage in the detection of less than 1 mm IFO. • U-HRCT has the potential to be used for screening of patients with suspected otosclerosis.

Increased Petrous Bone Uptake on 18 F-PSMA-1007 PET/CT Due to Otospongiosis

ABSTRACT

We report the case of a 74-year-old man who had undergone radical prostatectomy for prostatic cancer 6 months earlier. Elevated prostate-specific antigen during follow-up prompted 18 F-prostate-specific membrane antigen (PSMA) ligand PET/CT ( 18 F-PSMA-1007 PET/CT) to search for new manifestations of prostate cancer, revealing an increased focal uptake (SUV max , 5.9) in the left cochlear/pericochlear temporal bone and equivocal PSMA-RADS-3a external iliac nodes. Comparison with cone-beam CT and MRI showed that the focal temporal bone uptake corresponded to the typical morphological features of active otospongiosis (otosclerosis) in the context of a previously known long-standing otospongiosis.