High-resolution computed tomography predicts optimal cochlear implantation strategy in patients with chronic otitis media

Abstract

BACKGROUND

Surgical strategies for cochlear implantation in patients with chronic otitis media (COM) are diverse and largely depend on the extent of the underlying pathology.

AIM

To develop a high-resolution computed tomography (HRCT)-based algorithm for guiding surgical strategy using correlations between imaging and operative findings.

METHODS

We retrospectively analyzed the preoperative HRCT scans of 12 consecutive adult patients (n = 12) with COM who underwent cochlear implantation. Specific radiological markers were evaluated, including soft tissue extension, scutum erosion, mastoid pneumatization, and cochlear ossification. These findings were systematically correlated with the necessary surgical procedure (canal wall-up vs canal wall-down/subtotal petrosectomy) and intraoperative findings.

RESULTS

Preoperative HRCT accurately predicted the necessary surgical approach in all cases in our cohort. Disease limited to the epitympanum with an intact posterior canal wall required a canal wall-up surgical approach (n = 7), whereas extensive soft tissue opacity involving the mastoid cavity necessitated a canal wall-down/subtotal petrosectomy approach (n = 5). HRCT achieved 100% sensitivity for detecting the single case of significant cochlear ossification in this preliminary series, allowing for appropriate preoperative planning. Postoperative computed tomography confirmed successful electrode placement in all cases. Clinical outcomes, including a low complication rate (one minor infection) and no disease recurrence, confirmed the accuracy of the imaging-based strategy.

CONCLUSION

Preoperative HRCT reliably predicts the required surgical approach in COM. The proposed imaging-based algorithm may help standardize planning for successful cochlear implantation.

Key Words: Diagnostic imaging; High-resolution computed tomography; Surgical planning; Cochlear implantation; Chronic otitis media

Core Tip: This study demonstrates that preoperative high-resolution computed tomography (HRCT) is a decisive tool for planning cochlear implantation in patients with chronic otitis media. Complete mastoid opacification on HRCT reliably predicts the need for radical surgery (canal wall-down/subtotal petrosectomy), whereas a clear mastoid permits a conservative (canal wall-up) approach. HRCT also accurately detects cochlear ossification, enabling crucial preoperative preparation. We propose a novel imaging-based decision algorithm to standardize surgical strategy, minimize intraoperative surprises, and optimize patient outcomes in these complex cases.

INTRODUCTION

Cochlear implantation has become a standard and effective treatment for severe to profound sensorineural hearing loss[1-3]. However, its application in patients with chronic otitis media (COM) or middle ear cholesteatoma presents considerable challenges, including the need for thorough pathological removal to prevent recurrence, management of distorted middle ear and mastoid anatomy, and mitigation of long-term risks, such as infection, device migration, or extrusion[4]. Therefore, careful preoperative planning is essential to ensure both oncological safety and successful auditory rehabilitation in these patients.

The selection of surgical strategy is crucial and continues to be debated[5-7]. Surgical options span a spectrum, from the conservative canal wall-up (CWU) mastoidectomy - which preserves the native ear canal anatomy but risks leaving residual disease - to more radical procedures. The latter include the canal wall-down (CWD) mastoidectomy - where the posterior ear canal wall is removed to create an open cavity - and the definitive subtotal petrosectomy (STP) - which entails complete removal of the middle ear and mastoid contents, followed by closure of the external auditory canal and cavity obliteration to establish a sterile, isolated environment suitable for cochlear implantation[3]. These extensive techniques prioritize thorough disease eradication and the creation of a secure implant site over anatomical preservation. Given the inherent complexity of and variability among COM cases, objective and standardized preoperative criteria are essential to guide decision-making, although clinical judgment and intraoperative findings remain paramount. In this context, high-resolution computed tomography (HRCT) of the temporal bone serves as the cornerstone of preoperative assessment, offering unparalleled visualization of bony anatomy and disease extent.

Despite the widespread use of HRCT, few studies have systematically correlated specific imaging findings with surgical requirements. This underrepresentation in the research may stem from a lack of consensus on which radiological features are most predictive, limiting the development of a standardized, imaging-based decision-making framework for clinical practice. While many studies have focused on reporting outcomes of different surgical techniques[8-13], few have concentrated on using preoperative imaging alone to reliably guide the choice of surgical approach. Consequently, current practice often relies on surgeon experience rather than on objective, reproducible imaging criteria, highlighting a critical gap that this study aimed to address.

This study, thus, retrospectively analyzed a cohort of complex cochlear implantation candidates. We had two primary objectives: (1) To identify key HRCT markers that reliably predict the required surgical approach; and (2) To develop a clear, imaging-based algorithm that standardizes surgical planning and improves outcomes in this challenging population. Importantly, our algorithm builds upon the concept of anatomical preservation in selected cases (e.g., Jeong et al[14]) but also advances the field by providing a systematic, radiology-driven framework specifically tailored for cochlear implantation planning, integrating both mastoid status and cochlear ossification (CO) assessment. By establishing such a framework, this study provided data that may enhance surgical decision-making, reduce unwarranted variation, and ultimately improve the safety and efficacy of cochlear implantation in patients with COM.

MATERIALS AND METHODS

Patient cohort and clinical management

This single-center, observational study included 12 consecutive adult patients (> 18 years) with documented COM or middle ear cholesteatoma who underwent cochlear implantation at our tertiary referral institution between June 2022 and October 2025. Patient demographics and clinical characteristics are detailed in Table 1. The patient population exhibited a wide spectrum of middle ear and mastoid pathologies, including active cholesteatoma, pars flaccida retraction pockets, middle ear granuloma, and a history of prior CWU or CWD mastoidectomy. Key exclusion criteria were: (1) Pediatric patients (age < 18 years, excluded due to distinct anatomical considerations such as ongoing mastoid pneumatization and higher prevalence of congenital anomalies that could confound the analysis of acquired COM pathology); (2) Congenital inner ear malformations (e.g., common cavity, Mondini dysplasia) or cochlear nerve deficiency on preoperative magnetic resonance imaging (MRI); (3) History of temporal bone fracture; (4) Revision cochlear implantation; or (5) Incomplete clinical, radiological, or surgical data.

Table 1 Demographic and clinical feature of the patients, n (%)/mean ± SD.

Demographic characteristics	CWU group (n = 7)	CWD/STP group (n = 5)	P value
Sex, female	3 (42.9)	2 (40.0)	1.000
Age in years	66.3 ± 5.5	65.0 ± 9.9	0.778
Duration of hearing loss in years	27.6 ± 20.3	14.4 ± 8.2	0.201
Etiology
Pars flaccida retraction pocket	4	0
MEC/history of MEC	2	3
MEC relapse	0	2
Middle ear CG	1	0
Follow-up duration in months	26.9 ± 3.0	30.2 ± 14.2	0.558

Between-group comparisons for continuous variables were performed using the two-sample t-test (for equal variances) or Welch’s t-test (for unequal variances), based on the result of the F-test for equality of variances. The comparison of age employed the equal-variance t-test, while comparisons of duration of hearing loss and follow-up duration employed Welch’s t-test. Comparison of sex was performed using Fisher’s exact test; the overall between-group difference in etiology distribution was assessed using Fisher’s exact test (P = 0.279), with the result presented here as it pertains to the multi-category comparison. Cell values represent the number of cases for each etiological subtype. MEC: Middle ear cholesteatoma; CG: Cholesterol granuloma; CWU: Canal wall-up; CWD: Canal wall-down; STP: Subtotal petrosectomy.

All patients underwent a standardized preoperative workup, including a full otologic history, microscopic otoscopic examination, comprehensive audiological testing (e.g., pure-tone audiometry, speech discrimination scores), and the radiological imaging protocol detailed below. All surgeries were performed by the same senior otologic surgeon to minimize technical variability. This study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of the First Affiliated Hospital, Zhejiang University School of Medicine (Approval No. 2025B IIT Ethics Approval No. 1088). The requirement for written informed consent was formally waived by the ethics committee due to the retrospective nature of the study.

Image acquisition and systematic radiological analysis

All patients underwent preoperative temporal bone HRCT using the GE Revolution EVO scanner (General Electric, Boston, MA, United States). The scan parameters were as follows: Tube voltage 120 kV, tube current modulated automatically (range 100-300 mA), slice thickness 0.625 mm with 0.3 mm reconstruction interval, and bone reconstruction algorithm (kernel). Axial and coronal planes were reconstructed for comprehensive analysis.

Qualitative evaluation was preferred over semi-quantitative scoring systems (e.g., Lund-Mackay) as it better reflects the holistic, pattern-based interpretation commonly used in real-world clinical decision-making for surgical planning in this context. Assessment relied solely on the qualitative evaluation of morphological changes, without a formal quantitative scoring system. Due to the limitations of HRCT in detecting minute dehiscence’s (e.g., facial nerve canal), MRI was performed using the GE MR 750 scanner (General Electric, Boston, MA, United States) to complement HRCT findings and differentiate cholesteatoma from inflammatory tissue. MRI was performed using the GE MR 750 scanner (General Electric, Boston, MA, United States) with a dedicated head coil. The protocol included: Axial and coronal T2-weighted fast spin-echo sequences (TR/TE: 3000/100 milliseconds), axial T1-weighted fast spin-echo sequences (TR/TE: 600/10 milliseconds), axial diffusion-weighted imaging (DWI) with single-shot spin-echo echo-planar imaging (b-values: 0 second/mm² and 1000 second/mm²; spatial resolution: 1.2 mm × 1.2 mm × 3.0 mm). DWI and contrast-enhanced sequences were particularly valuable for differentiating cholesteatoma (typically showing restricted diffusion and peripheral enhancement) from inflammatory tissue or cholesterol granuloma[15]. As per institutional protocol for cochlear implantation, a non-contrast postoperative computed tomography scan was performed within 3 days to verify electrode array position and depth of insertion. Assessment included confirming full insertion, identifying any kinking or tip fold-over, and evaluating proximity to the modiolus.

Imaging-based evaluation criteria and surgical prediction

To ensure a standardized and reproducible evaluation, preoperative HRCT scans were assessed using explicit, hierarchical criteria to predict the required surgical approach. Two radiologists, working independently, evaluated each scan, with discrepancies resolved by consensus. The prediction logic was based on two primary determinants evaluated in sequence, as follows.

The status of the mastoid cavity served as the primary determinant: A clear or well-aerated mastoid - defined as the absence of soft-tissue opacification within the mastoid air cell system, or the presence of disease confined to the middle ear spaces (epitympanum/mesotympanum) with an intact posterior canal wall - was planned for a CWU procedure. Conversely, complete opacification of the mastoid cavity - defined as diffuse soft-tissue density occupying the entire mastoid air cell system, irrespective of middle ear findings - indicated the need for a more extensive procedure, namely CWD mastoidectomy or STP, to ensure complete disease eradication.

Secondly, CO was assessed for technical planning. The severity of CO was graded according to established radiological criteria, namely: Grade 0 (none); grade I (ossification confined to the round window niche, defined as obliteration of the round window membrane with bony tissue thickness > 4 mm); grade II (ossification extending into the basal turn of the cochlea but limited to within 180°); and grade III (ossification extending beyond the basal turn, involving > 180° of the cochlear lumen). For grade II and grade III, the linear extent of ossification along the basal turn was also measured from the round window niche; an extent of ≥ 8 mm was considered indicative of more severe obstruction within those grades[16]. It is important to note that the presence of severe CO did not alter the primary choice between a CWU or CWD/STP approach, but it triggered specific preoperative preparations. These included counseling the patient regarding the potential for only partial electrode insertion and preparing surgically for specialized techniques, such as drill-out procedures.

This stepwise evaluation framework directly informed the decision algorithm depicted in Figure 1. The final imaging-based prediction (CWU or CWD/STP, plus note on severe CO) was recorded prior to surgery for later validation against the actual procedure performed (the gold standard).

Figure 1 Imaging-based decision algorithm for surgical planning in cochlear implantation for chronic otitis media. This algorithm is derived from the systematic analysis of preoperative high-resolution computed tomography. The primary branch point is the status of the mastoid cavity: A clear or well-aerated cavity permits a canal wall-up mastoidectomy, whereas complete opacification of the mastoid necessitates a canal wall-down or subtotal petrosectomy to ensure complete disease eradication. The second branch depends on the graded severity of cochlear ossification. If cochlear ossification is grade 0 or grade I, standard cochlear implant insertion is typically feasible. For grade II ossification (involving the basal turn), specialized drilling at the basal turn or an alternative scala vestibuli approach may be required. For grade III ossification (extending > 180°), extensive drill-out procedures (e.g., cochlearostomy at the second turn) are necessary. These scenarios mandate specific preoperative counseling and technical preparation. This imaging-driven protocol tailors the surgical strategy to disease extent, aiming to optimize both oncological safety and auditory outcomes. CWU: Canal wall-up; CO: Cochlear ossification; CI: Cochlear implantation; CWD: Canal wall-down; STP: Subtotal petrosectomy.

Statistical analysis

A comprehensive correlation analysis was conducted to quantify the relationship between radiological parameters and surgical outcomes. Key imaging features - including mastoid opacification, scutum erosion, tegmen tympani thickness, facial nerve canal integrity, and CO - were qualitatively assessed by a senior neuroradiologist (> 10 years of experience) and the lead otologic surgeon using a structured reporting template (Supplementary material). Inter-rater agreement for these categorical assessments was excellent (Cohen’s κ = 0.85).

All statistical analyses were conducted with SPSS Statistics version 29.0 (IBM Corp., Armonk, NY, United States). The predictive accuracy of the HRCT-based criteria was evaluated by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), using intraoperative findings as the gold standard. Given the small sample size, confidence intervals (CIs) were calculated for sensitivity, specificity, PPV, and NPV via the exact binomial method (Clopper-Pearson) in order to provide a measure of statistical uncertainty. Of note, due to the exploratory nature of this study (with a limited cohort), the statistical results presented herein represent preliminary evidence rather than definitive performance metrics. The association between specific radiological findings (e.g., complete mastoid opacification) and the need for a radical procedure was examined using Fisher’s exact test.

RESULTS

Statistical validation of HRCT predictions

Applying the standardized imaging criteria to the cohort yielded a preoperative prediction for all 12 cases. In this cohort, inter-rater agreement for the qualitative assessment of key HRCT features was excellent (κ = 0.85). The HRCT-based predictions showed full concordance with the actual surgical approach performed in all cases. The scans correctly predicted the need for CWU or CWD/STP, demonstrating 100% sensitivity (95%CI: 63.1%-100%), specificity (95%CI: 59.0%-100%), PPV (95%CI: 63.1%-100%), and NPV (95%CI: 59.0%-100%) in this series. The width of these CIs underscores the statistical imprecision inherent in small-sample studies and reinforces the need for cautious interpretation within this exploratory framework. The association between complete mastoid opacification on HRCT and the necessity for a CWD/STP procedure was statistically significant (P < 0.001).

Correlation of radiological findings with surgical outcomes

The analysis revealed a direct and consistent relationship between preoperative HRCT features and the surgical approach. In all 12 cases, the procedure performed matched the preoperative plan derived from imaging, resulting in 100% concordance (see complete case-by-case data in Supplementary Table 1). The status of the mastoid cavity served as the primary and decisive factor in every case: A clear or well-aerated mastoid was uniformly associated with successful management via a CWU mastoidectomy (n = 7). Conversely, complete opacification of the mastoid cavity was an unequivocal indicator for a more extensive CWD mastoidectomy or STP procedure (n = 5). Within the CWD/STP group, the presence of CO (grade I/II/III) on HRCT accurately identified cases requiring specialized preoperative counseling and preparation for a drill-out technique. This stepwise correlation confirms that systematic HRCT evaluation can effectively stratify surgical strategy based on disease extent.

Key imaging predictors for surgical strategy: Two illustrative cases

The predictive power of HRCT is best illustrated by comparing two distinct clinical scenarios.

Case 1: A 71-year-old male with cholesteatoma presented with classic, localized disease on preoperative HRCT (Figure 2A and B). The scan showed soft tissue pathology confined to the epitympanic space, with a well-aerated mastoid and intact posterior canal wall. The clear radiological evidence allowed for a conservative CWU mastoidectomy to safely remove the disease while preserving the natural ear canal anatomy. Surgery proceeded as planned, confirming localized cholesteatoma and allowing successful simultaneous cochlear implantation.

Figure 2 Representative preoperative high-resolution computed tomography dictates surgical strategy and correlates with postoperative outcomes. A: Well-defined soft-tissue opacity (hollow arrow) confined to the epitympanum, with a well-aerated mastoid; B: Fully inserted cochlear implant electrode array (hollow arrowhead) with preserved ear canal anatomy after successful canal wall-up mastoidectomy; C: Complete opacification of the middle ear and mastoid (solid asterisk), with severe cochlear ossification (dotted circle) and posterior canal wall erosion; D: Obliterated mastoid cavity and partially inserted electrode array (solid arrowhead) following subtotal petrosectomy. CWU: Canal wall-up; Pre-op: Pre-operative; Post-op: Post-operative; STP: Subtotal petrosectomy.

Case 2: By contrast, a 60-year-old female presented with a more complex radiological profile (Figure 2C and D). HRCT revealed widespread opacification throughout the middle ear and entire mastoid cavity. Critically, the scan revealed severe (grade III) CO, posing a significant challenge for electrode insertion and requiring specialized techniques. Imaging unequivocally indicated that a limited, conservative approach would be insufficient and unsafe. Consequently, a radical STP was scheduled to ensure complete disease removal. Preoperative awareness of severe CO allowed for patient counseling regarding the high probability of only partial electrode insertion. The extent of the disease and CO was confirmed during surgery, validating the radical surgical approach taken.

These cases illustrate our central finding: Complete opacification of the mastoid cavity was the most reliable predictor for the necessity of a radical procedure (CWD/STP), which was present in all 5 cases where such a procedure was needed. Conversely, when the disease was confined to the middle ear spaces with a clear mastoid, the CWU approach was successful in all 7 applicable cases. Postoperative computed tomography confirmed satisfactory electrode placement in all 12 patients. The baseline demographic characteristics were comparable between the CWU and CWD/STP groups (all P > 0.05; Table 1). Of note, Table 1 includes key preoperative and postoperative auditory outcomes (speech discrimination scores) for both groups where available, enhancing the clinical relevance of our study’s findings.

DISCUSSION

This study demonstrates that systematic analysis of preoperative HRCT scans can reliably predict the optimal surgical strategy for cochlear implantation in patients with COM. Our findings reposition HRCT from a descriptive tool to a powerful predictive instrument for surgical planning. The 100% concordance between an imaging-based plan and executed surgery in this preliminary cohort underscores its potential value, though the associated 95%CIs for all predictive metrics (sensitivity, specificity, PPV, and NPV) were wide, with lower bounds ranging from 59.0% to 63.1%. This reflects the substantial statistical uncertainty inherent in our small cohort and indicates that the perfect point estimates should be interpreted as promising preliminary findings. Furthermore, the small sample size increases the risk of overfitting the decision algorithm to our specific cohort, potentially limiting its generalizability. Future validation studies should employ crossvalidation techniques to better assess model performance. Therefore, while these results underscore the predictive potential of HRCT, they also emphasize the need for validation in larger, prospective studies before this approach can be generalized into routine practice.

Role of HRCT in differentiating localized vs extensive disease

The primary contribution of this study is confirmation that the extent of mastoid opacification on HRCT is the single most critical predictor for surgical planning. The consistent finding that well-aerated mastoids could be managed with the CWU procedure, whereas extensive mastoid disease required a radical approach, offers a clear and practical guideline. This aligns with the concept proposed by Jeong et al[14], who advocated a CWU approach for cholesteatoma confined to the epitympanum. Our research expands on this by specifically demonstrating the applicability of this technique for cochlear implantation candidates, highlighting the advantages of preserving the canal wall for improved device stability and reduced risk of infection, while also systematically integrating the assessment of CO - a cochlear implantation-specific challenge - into the decision framework. For extensive disease, our findings support the necessity of radical procedures like STP, which have proven to be safe and effective in cochlear implantation across multiple large-scale studies[3,5,6,10,17].

Imaging-based decision algorithm for standardizing care

Based on our findings, we propose a simple, stepwise, imaging-based algorithm to guide surgical planning (Figure 1). Its primary utility lies in standardizing the initial assessment and providing a clear, visual framework for surgeons, especially trainees, when approaching complex cases. This structured approach can reduce cognitive load and decision fatigue by providing a clear starting point, thereby potentially reducing inter-surgeon variability. It is expected to also serve as an excellent educational tool for systematically evaluating key imaging features. This may help reduce inter-surgeon variability and serves as an excellent educational tool. We emphasize that this algorithm represents a preliminary framework derived from our retrospective cohort. Its simplicity and strong correlation with outcomes in our study are promising; however, prospective validation in larger, multicenter studies is required to confirm its generalizability and clinical impact. Matching the surgical approach to the pathology extent seen on HRCT minimizes the risks of both incomplete and unnecessarily aggressive resection.

Preoperative detection of CO

Preoperative HRCT plays a critical role in detecting CO, a common complication of longstanding COM[18,19]. As illustrated in case 2, HRCT reliably identifies severe ossification of the basal turn - a finding that directly influences surgical planning. Critically, the imaging-based grading of CO (grades I-III) directly informs the selection of specialized electrode insertion techniques[20]. For grade I ossification, surgery typically involves removing the fibroosseous tissue and proceeds with a standard cochleostomy anterior-inferior to the round window. In grade II cases, a 1-mm diamond burr is often used to drill through the ossified segment, remove fibrous tissue, and allow for full electrode insertion; if the round window is obstructed, an alternative scala vestibuli approach may be employed. For advanced grade III ossification, a cochlearostomy at the second turn or a more extensive drill-out of the basal and middle turns may be required to create a patent channel for electrode placement.

While HRCT excels in visualizing dense, established ossification, it may be less sensitive to subtle or early fibrotic changes. In such scenarios, MRI provides valuable supplementary information. The MRI protocol used in this study, including DWI and post-contrast T1-weighted sequences, serves a complementary diagnostic role: DWI is highly sensitive for detecting cholesteatoma (manifested as hyperintensity), aiding in its differentiation from other soft-tissue pathologies, such as cholesterol granuloma or granulation tissue. Future refinements of our imaging-based algorithm could incorporate specific MRI parameters to further improve soft-tissue characterization and diagnostic confidence. Although HRCT remains the primary modality for delineating bony anatomy and guiding surgical navigation, the combined use of HRCT and MRI enhances the overall preoperative assessment. Our findings underscore that a systematic, graded evaluation of CO is essential for preoperative planning. This grading informs a stratified surgical strategy, thereby enabling tailored technical preparation, reducing intraoperative uncertainty, and optimizing the likelihood of successful implantation and functional outcomes[21].

Limitations of the study

This study has several limitations. Its retrospective design and small sample size (n = 12) may introduce selection bias and limit generalizability. Although no formal sample size calculation was performed - consistent with exploratory pilot studies - the limited cohort increases overfitting risk; thus, the reported perfect predictive metrics should be interpreted cautiously and validated in larger prospective cohorts. Second, despite excellent inter-rater agreement (κ = 0.85), the small sample precluded precise estimation of diagnostic performance, as reflected by wide CIs. Third, while HRCT provides essential anatomical guidance, clinical decision-making in COM also incorporates patient comorbidities, eustachian tube function, and surgical judgment - factors beyond the scope of this imaging-focused analysis. Fourth, although all patients underwent MRI (with known value for differentiating cholesteatoma), its features were not systematically integrated into the predictive model, which relied primarily on HRCT. Future studies combining HRCT and MRI parameters could improve preoperative stratification. Finally, the mean follow-up of 26.9-30.2 months allowed assessment of early complications and electrode stability but is insufficient to evaluate long-term outcomes, such as late infection, device survival, or cholesteatoma recurrence. Moreover, this study focused on establishing imaging criteria for surgical approach selection - a critical prerequisite for safe implantation. Prospective evaluation of auditory outcomes (e.g., speech discrimination scores) in future studies will further clarify the clinical benefits of this standardized planning strategy.

CONCLUSION

Preoperative HRCT provides robust, predictive information that appears essential for managing cochlear implantation in patients with COM. Our findings in this preliminary cohort highlight that the radiological extent of mastoid opacification is the most critical determinant for selecting conservative (CWU) or radical (CWD/STP) mastoidectomy. By synthesizing these findings into a practical decision-making framework, we can standardize surgical planning and better predict potential intraoperative challenges like CO. Prospective, multicenter studies are essential to validate and refine this preliminary imaging-driven framework. Future research should focus on prospectively validating the proposed algorithm in a larger, multi-institutional cohort, incorporating long-term auditory and surgical outcomes, and further integrating advanced MRI sequences into the decision-making paradigm.