Assessing Stapes Piston Position Using Computed Tomography: A Cadaveric Study

Ultra-high-resolution CT of the temporal bone: The end of stapes prosthesis dimensional error and correlation with patient symptoms

PURPOSE

To describe the reliability of ultra-high-resolution computed tomography (UHR-CT) in the measurement of titanium stapes prostheses using manufacturer data as a reference.

MATERIALS AND METHODS

This retrospective study included patients treated by stapedectomy with titanium prostheses who underwent UHR-CT between January 2020 and October 2023. Images were acquired using an ultra-high-resolution mode (slice thickness: 0.25 mm; matrix, 1024 × 1024). Two radiologists independently evaluated the length, diameter, and intra-vestibular protrusion of the prosthesis. Post-operative air-bone gaps (ABGs) were recorded.

RESULTS

Fourteen patients were enrolled (mean age, 44.3 ± 13.8 [SD] years, 9 females), resulting in 16 temporal bone UHR-CTs. The exact length was obtained in 81.3 % (n = 13/16) and underestimated by 0.1 to 0.3 mm in the remaining 18.7 % (n = 3/16) CT scans for both readers (mean misestimation: -0.02 ± 0.06 [SD] mm, overall underestimation of 0.43 %). The exact diameter was reported in 75 % (n = 12/16) and 87.5 % (n = 14/16) of the CT scans for readers 1 and 2, respectively, and was off by 0.1 mm in all discrepancies (mean misestimation: 0.01 ± 0.04 [SD] mm, overall overestimation of 2.43 %). Intravestibular prosthesis protrusion was of 0.5 ± 0.43 [SD] mm (range: 0-1) and 0.49 ± 0.44 [SD] mm (range: 0-1.1) for readers 1 and 2, respectively, and did not correlate with ABGs (r = 0.25 and 0.22; P = 0.39 and 0.47 for readers 1 and 2, respectively). Intra and interobserver agreements were excellent.

CONCLUSION

UHR-CT provides 99.6 % and 97.6 % accuracy for prosthesis length and diameter measurements, respectively.

High-Resolution CT Imaging of the Temporal Bone: A Cadaveric Specimen Study

Objective  Super-high and ultra-high spatial resolution computed tomography (CT) imaging can be advantageous for detecting temporal bone pathology and guiding treatment strategies. Methods  Six temporal bone cadaveric specimens were used to evaluate the temporal bone microanatomic structures utilizing the following CT reconstruction modes: normal resolution (NR, 0.5-mm slice thickness, 512 ² matrix), high resolution (HR, 0.5-mm slice thickness, 1,024 ² matrix), super-high resolution (SHR, 0.25-mm slice thickness, 1,024 ² matrix), and ultra-high resolution (UHR, 0.25-mm slice thickness, 2,048 ² matrix). Noise and signal-to-noise ratio (SNR) for bone and air were measured at each reconstruction mode. Two observers assessed visualization of seven small anatomic structures using a 4-point scale at each reconstruction mode. Results  Noise was significantly higher and SNR significantly lower with increases in spatial resolution (NR, HR, and SHR). There was no statistical difference between SHR and UHR imaging with regard to noise and SNR. There was significantly improved visibility of all temporal bone osseous structures of interest with SHR and UHR imaging relative to NR imaging ( p  < 0.001) and most of the temporal bone osseous structures relative to HR imaging. There was no statistical difference in the subjective image quality between SHR and UHR imaging of the temporal bone ( p  ≥ 0.085). Conclusion  Super-high-resolution and ultra-high-resolution CT imaging results in significant improvement in image quality compared with normal-resolution and high-resolution CT imaging of the temporal bone. This preliminary study also demonstrates equivalency between super-high and ultra-high spatial resolution temporal bone CT imaging protocols for clinical use.

Prognostic factors for duration of vertigo after stapes surgery via a time-to-event analysis

BACKGROUND

Vertigo or dizziness after stapes surgery occurs sometimes, and it is generally temporary. However, while rare, it can be prolonged.

AIMS/OBJECTIVES

To investigate the prognostic factors for duration of vertigo following stapedotomy using a time-to-event analysis.

MATERIALS AND METHODS

The present study included a total of 35 primary ears (26 with otosclerosis and nine with congenital stapes fixation) from 31 patients. We assessed residual rates of nystagmus and complaints of subjective vestibular symptoms using Kaplan-Meier time-to-event methods.

RESULTS

Postoperative spontaneous nystagmus was observed in 23 (65.7%) ears, and postoperative subjective vestibular symptoms were confirmed in 27 (77.1%) ears. The total mean duration of postoperative spontaneous nystagmus and subjective vestibular symptoms was 9.8 (range: 0-158) and 33.9 days (0-732), respectively. A history of stapes surgery in the opposite ear was a significant predictive factor for prolonged nystagmus and subjective vestibular symptoms (p = .0059 and p = .0146).

CONCLUSIONS AND SIGNIFICANCE

For individuals with a history of stapes surgery in the opposite ear, spontaneous nystagmus and vertigo/dizziness sensations following stapedotomy may persist for a longer duration than in those without a history of stapes surgery in the opposite ear.

Titanium and Platinum-Fluoroplastic Stapes Prostheses Visualization on Cone Beam Computed Tomography and High-Resolution Computed Tomography

Objective: The aim of this study was to evaluate whether stapes prostheses can be visualized with less metal artifacts and therefore more accurately on cone beam computed tomography in comparison to computed tomography imaging. Recent studies have shown that cone beam computed tomography has advantages when imaging metal artifacts. Patients with hearing loss or vertigo, who have undergone stapedotomy, often present a challenge for otologic surgeons. Imaging studies can deliver crucial additional information. Methods: A retrospective analysis of imaging studies and clinical data in a tertiary care center were carried out. Forty-one patients with forty-five implanted ears were evaluated in the study. All included patients had been implanted with a platinum-fluoroplastic (n = 19) or titanium (n = 26) piston and subsequently had undergone imaging months or years after surgery for various reasons. Patients underwent computed tomography or cone beam computed tomography of the temporal bone depending on availability. Piston visualization, prosthesis length, vestibular intrusion and audiologic results were compared between the groups. Piston position on imaging studies were compared to intraoperative findings. Results: Functional length measurements of all prostheses were carried out with a mean error of -0.17 mm (±0.20). Platinum-fluoroplastic protheses were significantly underestimated in length compared to titanium prostheses. To analyze the material-dependent difference in the measurement errors of the imaging techniques the interaction was tested in an ANOVA model and showed no statistically significant result (p = 0.24). The blinded neuroradiologist viewed two implants, both platinum-fluoroplastic pistons, as located outside of the vestibule due to an underestimation of the prothesis length and the missing radiodensity of the lower end of the prosthesis. Conclusion: Surgeons and radiologists should be aware of the different types and radiologic features of stapes prostheses and the missing radiodensity of some protheses parts. Cone beam computed tomography is an imaging alternative with a potential advantage of reduced radiation in patients after stapes surgery suffering from vertigo or hearing loss to evaluate piston position.

Stapes piston insertion depth and clinical correlations

Background: The insertion of the stapes piston within the vestibule provides the physical basis for a successful stapedotomy. An insertion depth of 0.5 mm is recommended to avoid the dislocation of the stapes prosthesis (e.g. sneezing). Aims: The objective of this study is to analyze the depth of stapes prosthesis insertion and its correlation with clinical outcome. Material and methods: We observed in a retrospective case series 39 otosclerosis patients after a stapedotomy and a postoperative performed flat panel tomography/cone beam CT. The evaluation included the radiologically found depth of prosthesis insertion within the vestibule, the vestibule depth, and the correlation with the bone conduction (BC) threshold, vertigo, and tinnitus. Results: Insertion depth varied between 0.2 and 1.6 mm (mean 0.74 mm). The ratio of insertion depth versus the vestibule depth was between 8% and 59% (mean 26.6%). We observed no correlation between the insertion depth, the length of the prosthesis, the ratio of insertion depth/vestibule depth, postoperative BC, appearance of vertigo, or tinnitus. Conclusions and significance: In our group, we observed no significant relation between insertion depth of the stapes piston, postoperative vertigo, tinnitus, or decrease of the BC.

Ultrahigh-resolution CT scan of the temporal bone

OBJECTIVE

Ultrahigh-resolution CT (U-HRCT) provides better spatial resolution than conventional multi-detector row CT (ConvCT) and could be expected to identify microstructures with its 0.25-mm collimation, 1792 channels and 160 detector rows, 0.4 × 0.5 mm focus size, and a 1024 matrix. The aim of the study was to evaluate key anatomic structures in temporal bone using U-HRCT comparing it to ConvCT.

MATERIALS AND METHODS

A total of 30 patients (14 males and 16 females; age range, 8-82 years; median 49 years) underwent both U-HRCT and ConvCT. All CT images were obtained with 0.5 mm section thickness and a 512 × 512 matrix, and field of view of 80 mm. Transverse scans were acquired in a plane parallel to the orbitomeatal plane in the helical mode with 120 kV. Images of the 30 temporal bones of unaffected side were reviewed by two independent neuroradiologists who rated the visibility of key anatomic structures for both U-HRCT and ConvCT. The ratings between U-HRCT and ConvCT were compared using Wilcoxon matched-pairs signed rank test. The interobserver agreement on the rating of stapedius tendon was evaluated using weighted κ statistics.

RESULTS

Excellent interobserver agreement was shown for U-HRCT (κ = 0.920), whereas good agreement was obtained for ConvCT (κ = 0.733). According to both observers, stapedius tendon was more clearly visualized using U-HRCT than ConvCT (p < 0.0001). All other anatomic structures were well visualized using both CT scanners.

CONCLUSION

The anatomy of temporal bone is more conspicuous on U-HRCT than on ConvCT because of its ultra-high-resolution detector. U-HRCT may provide beneficial information for determining surgical indication or procedures.

Magnetic resonance imaging evaluation of endolymphatic hydrops andpost-operative findings in cases with otosclerosis

CONCLUSIONS

The presence of endolymphatic hydrops (EH) in the vestibule on magnetic resonance imaging (MRI) might be a high-risk factor for complications in cases that are candidates for stapes surgery.

OBJECTIVE

Pre-operative detection of EH could be valuable in cases that are candidates for stapes surgery to prevent unpredictable complications following surgery. Pre-operative MRI findings and post-operative findings following stapes surgery were compared to evaluate the efficacy of such MRI evaluation for the management of cases with otosclerosis.

SUBJECTS AND METHODS

Sixteen cases who underwent pre-operative evaluation by 3T MRI performed 4 h after intravenous injection of gadolinium and stapes surgery for otosclerosis were recruited. Imaging data concerning the degree of EH in the vestibule and cochlea were compared with post-operative clinical findings for all cases.

RESULTS

Mild EH in the cochlea or the vestibule was observed in eight ears and one ear, respectively, whereas one ear showed significant EH both in the cochlea and the vestibule. The post-operative course was uneventful in 12 of 14 cases with no EH in the vestibule, and the other two cases had a short period of dizziness, but two cases with EH in the vestibule had a long period of dizziness.

MPR-CT Imaging for Stapes Prosthesis: Accuracy and Clinical Significance

OBJECTIVES

The aims of this article are: 1) to re-evaluate the accuracy of multiple planar reconstruction computed tomography (MPR-CT) imaging on stapes-prosthesis parameters, and 2) to clarify possible relationships between prosthesis intravestibular depth and postoperative hearing outcomes.

PATIENTS

Seventy patients (46 women and 24 men; 32 right and 38 left sides) with the mean age of 40 years (range, 19-62 yr) with clinical otosclerosis.

INTERVENTION(S)

All patients underwent stapedotomy and were implanted with the same type of titanium piston prosthesis by the same surgeon.

MAIN OUTCOME MEASURE(S)

Postoperative MPR-CTs were obtained at patients' follow-up visits. The length and intravestibular depth of the stapes prosthesis (including absolute and relative depth) were calculated from the MPR-CT imaging. Relationships between the intravestibular depth of the prosthesis and hearing outcomes (pre- and postoperative audiograms) were analyzed using Spearman correlation analyses.

RESULTS

The length of the prosthesis was overestimated by 1.8% (0.1 mm) by the MPR-CT imaging. Axial and coronal measurements were significantly correlated (p < 0.05). There was great intersubject variability in hearing outcomes differed insignificantly, regardless of intravestibular depth within the security range. No relationships were found between the intravestibular depth of the stapes prosthesis, as measured with MPR-CT, and postoperative hearing results.

CONCLUSIONS

MPR-CT can provide an accurate estimation of stapes prosthesis parameters. However, the prosthesis intravestibular depth did not seem to affect postoperative hearing outcomes.

[Quality control following reconstructive middle ear surgery: from bench to bedside]

BACKGROUND

The ongoing improvement of imaging quality nowadays focuses increasingly more on immediate quality evaluation of surgical measures.

METHODS

Rotational tomography (RT) has been experimentally proven to be an alternative imaging technique to computed tomography (CT) in terms of quality and postoperative localization of middle ear implants in temporal bones. Based on these results imaging parameters were determined in the form of a surgical check list in order to systematically check individual but important surgical reconstructive steps.

RESULTS

The positive benefit of RT concerning immediate and significant postoperative quality control was confirmed by a patient study. The surgical check list was successfully implemented under clinical framework requirements. Among these standardized parameters the determined angulation of inserted middle ear implants was given outstanding significance due to the predictive value concerning functional outcome.

CONCLUSION

The RT procedure has been proven to be a reliable imaging tool for postoperative quality control following reconstructive middle ear surgery.

Radiological control of the floating mass transducer attached to the round window

The surgical rehabilitation of mixed hearing losses can be performed by coupling the floating mass transducer of the Vibrant Soundbridge to the round window. The quality of coupling the floating mass transducer to the round window is crucial for the audiological outcome. It was the aim of this study to further observe the different patterns of floating mass transducer position at the round window. We compared twenty patients with mixed hearing loss implanted with a floating mass transducer attached to the round window and 24 surgeries between 5/2007 and 6/2010. An evaluation of the chronological observation of the flat panel angiography-controlled position of the floating mass transducer at the round window with relation to the surgical report and the audiological outcome was done. We observed no changes in the mean pre- and postbone conduction thresholds. The floating mass transducer position was variable and could be radiologically classified and correlated with the audiologically outcome. A learning curve was observed from the earlier to later implantations. Postoperative, radiological evaluation of the location and angle of the floating mass transducer by means of flat panel tomography allowed us to classify the floating mass transducer position at the round window into 4 groups.