Cone beam computed tomography and histological evaluations of a straight electrode array positioning in temporal bones

Variation in cochlear size: A systematic review

BACKGROUND

Advancements in imaging and implantation technology have invited reexamination of the classic teaching that the human cochlea maintains uniform size across demographics. Yet, studies yield conflicting results and relatively few broad systematic reviews have examined cochlear size variation.

PURPOSE

The purpose of this study is to quantify cochlear variability across eight different measurement categories and suggest normative values and ranges for each with consideration of disease state and gender where possible.

METHODS

A systematic search was conducted up to October 1, 2022, using the search terms "Cochlea/anatomy and histology"[Mesh]) AND 'size'" with filters "Humans" and "English" across three databases (PubMed, CINAHL, Medline). Further inclusion criteria involved reporting of numerical measurements in any of the eight included categories.

RESULTS

Of the 625 articles manually reviewed for relevance by title and abstract, 91 were selected for full-text review and 33 met all eligibility criteria. 5,791 cochleae were included and weighted means and ranges were calculated: "A" value (defined as the distance from the round window, through the modiolus, to the oppsite lateral wall) = 9.23 mm (8.43-10.4 mm, n = 2559); cochlear duct length (CDL) = 33.04 mm (range 28.2-36.4 mm, n = 2252); cochlear height = 5.14 mm (2.8-6.9 mm, n = 2098); the basal turn lumen diameter = 2.09 mm (1.7-2.2 mm, n = 617); "B" value (defined as perpendicular to "A" value and in the same plane) = 6.52 mm (5.73-6.9 mm, n = 908); width of the basal turn = 6.4 mm (6.22-6.86 mm, n = 356); height of the basal turn = 1.96 mm (1.77-2.56 mm, n = 204); length of the basal turn 21.87 mm (21.03-22.5 mm, n = 384).

CONCLUSION

A notable size range exists across the eight different cochlear parameters considered and we provide normative values for each measurement. Females tend to have smaller CDL and "A" value than males and the sensorineural hearing loss patients had smaller CDL and "A" value but larger cochlear height than the general population.

Trauma After Cochlear Implantation: The Accuracy of Micro-Computed Tomography and Cone-Beam Fusion Computed Tomography Compared With Histology in Human Temporal Bones

HYPOTHESIS

Micro-computed tomography (micro-CT) and cone-beam computed tomography (CBCT), in conjunction with the image fusion technique, may provide similar results for trauma assessment after cochlear implantation, with respect to the trauma evaluation in preclinical cochlear implant (CI) studies, as the histology.

BACKGROUND

Before clinical use, novel cochlear implant (CI) designs are tested in temporal bone (TB) studies for usability and risk evaluation. The criterion standard for evaluating intracochlear insertion trauma and electrode location has historically been with histological samples. Progress of modern imaging technology has created alternatives to classic histology. This study compares the micro-CT and CBCT fusion images between histological samples in a preclinical CI study.

METHODS

Fourteen freshly frozen TBs were inserted with a lateral wall research CI electrode. All TBs were scanned with CBCT preoperatively and postoperatively. After insertion, the TBs were prepared for micro-CT and histology. Twelve TBs underwent first a micro-CT and then the histological process. The CBCTs were used for image fusion, and all three different methods were used for intracochlear trauma evaluation. The results were compared between methods.

RESULTS

There were 4 of 14 translocations detected with the fusion image method and 3 of 12 with the micro-CT and histology. When compared, the trauma grades converged and were not statistically significant.

CONCLUSION

The trauma grading based on micro-CT is comparable to the histology. The image fusion technique based on CBCT is less accurate because it relies on an empirical assumption of the basal membrane localization, but it is clinically applicable.

Human Bone Typing Using Quantitative Cone-Beam Computed Tomography

INTRODUCTION

Bone typing is crucial to enable the choice of a suitable implant, the surgical technique, and the evaluation of the clinical outcome. Currently, bone typing is assessed subjectively by the surgeon.

OBJECTIVE

The aim of this study is to establish an automatic quantification method to determine local bone types by the use of cone-beam computed tomography (CBCT) for an observer-independent approach.

METHODS

Six adult human cadaver skulls were used. The 4 generally used bone types in dental implantology and orthodontics were identified, and specific Hounsfield unit (HU) ranges (grey-scale values) were assigned to each bone type for identification by quantitative CBCT (qCBCT). The selected scanned planes were labelled by nonradiolucent markers for reidentification in the backup/cross-check evaluation methods. The selected planes were then physically removed as thick bone tissue sections for in vitro correlation measurements by qCBCT, quantitative micro-computed tomography (micro-CT), and quantitative histomorphometry.

RESULTS

Correlation analyses between the different bone tissue quantification methods to identify bone types based on numerical ranges of HU values revealed that the Pearson correlation coefficient of qCBCT with micro-CT and quantitative histomorphometry was R = 0.9 (P = .001) for all 4 bone types .

CONCLUSIONS

We found that  qCBCT can reproducibly and objectively assess human bone types at implant sites.

Insight in to the Awareness of CBCT as an Imaging Modality in the Diagnosis and Management of ENT Disorders: A Cross Sectional Study

The advent of Cone-beam computed tomography (CBCT), has revolutionized 3D imaging in dentistry. CBCT has enormous potential to be used as an alternative imaging modality by Otolaryngologists. But their knowledge regarding CBCT is limited. The study aims to evaluate the awareness of CBCT as an imaging modality among Ear, nose and Throat (ENT) practitioners. The validated questionnaire was sent by email and the participants were asked to fill the google form through the link provided to record the responses. The participants were asked to answer 25 multiple choice questions regarding the general information and practice related to CBCT imaging. Data was evaluated according to the descriptive statistics and the Chi-square test was used to determine the test of significance. The response rate for this study was 84.4%. The mean age of the participants was 44.9 ± 11.3. 69% of the respondents were academicians,14.2% had exclusive clinical practice, and 16.8% had both clinical and academic exposure. Among the study population, 76.8% had never advised CBCT in their practice. Only 10.3% of the study participants were aware of the potential of CBCT in ENT disorders. The mean knowledge, attitude and practice scores were very low regarding the applications of CBCT. Most of the study participants advised CBCT for maxillofacial fractures (78.1%) and was statistically significant p < 0.05. The knowledge about various advantages and clinical applications of CBCT among Otolaryngologists is limited. However, continuing medical education and inclusion in the medical curriculum will increase the scope and awareness about CBCT among ENT fraternity.

Evaluating cochlear insertion trauma and hearing preservation after cochlear implantation (CIPRES): a study protocol for a randomized single-blind controlled trial

Background

In order to preserve residual hearing in patients with sensorineural hearing loss (SNHL) who receive a cochlear implant (CI), insertion trauma to the delicate structures of the cochlea needs to be minimized. The surgical approach comprises the conventional mastoidectomy-posterior tympanotomy (MPT) to arrive at the middle ear, followed by either a cochleostomy (CO) or the round window (RW) approach. Both techniques have their benefits and disadvantages. Another important aspect in structure preservation is the design of the electrode array. Two different designs are used: a “straight” lateral wall lying electrode array (LW) or a “pre-curved” perimodiolar lying electrode array (PM). Interestingly, until now, the best surgical approach and design of the implant is uncertain. Our hypothesis is that there is a difference in hearing preservation outcomes between the four possible treatment options.

Methods

We designed a monocenter, multi-arm, randomized controlled trial to compare insertion trauma between four groups of patients, with each group having a unique combination of an electrode array type (LW or PM) and surgical approach (RW or CO). In total, 48 patients will be randomized into one of these four intervention groups. Our primary objective is the comparison of postoperative hearing preservation between these four groups. Secondly, we aim to assess structure preservation (i.e., scalar translocation, with basilar membrane disruption or tip fold-over of array) for each group. Thirdly, we will compare objective outcomes of hearing and structure preservation by way of electrocochleography (ECochG).

Discussion

Cochlear implantation by way of a cochleostomy or round window approach, using different electrode array types, is the standard medical care for patients with severe to profound bilateral sensorineural hearing loss, as it is a relatively simple and low-risk procedure that greatly benefits patients. However, loss of residual hearing remains a problem. This trial is the first randomized controlled trial that evaluates the effect of cochlear insertion trauma of several CI treatment options on hearing preservation.

Trial registration

Netherlands Trial Register (NTR) NL8586. Registered on 4 May 2020. Retrospectively registered; 3/48 participants were included before registration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05878-2.

A novel cochlear measurement that predicts inner-ear malformation

The A-value used in cochlear duct length (CDL) estimation does not take malformed cochleae into consideration. The objective was to determine the A-value reported in the literature, to assess the accuracy of the A-value measurement and to evaluate a novel cochlear measurement in distinguishing malformed cochlea. High resolution Computer Tomography images in the oblique coronal plane/cochlear view of 74 human temporal bones were analyzed. The A-value and novel C-value measurement were evaluated as predictors of inner ear malformation type. The proximity of the facial nerve to the basal turn was evaluated subjectively. 26 publications report on the A-value; but they do not distinguish normal vs. malformed cochleae. The A-values of the normal cochleae compared to the cochleae with cochlear hypoplasia, incomplete partition (IP) type I, -type II, and -type III were significantly different. The A-value does not predict the C-value. The C-values of the normal cochleae compared to the cochleae with IP type I and IP type III were significantly different. The proximity of the facial nerve to the basal turn did not relate to the type of malformation. The A-value is different in normal vs. malformed cochleae. The novel C-value could be used to predict malformed anatomy, although it does not distinguish all malformation types.

Comprehensive Analysis of Factors Affecting Cochlear Size: A Systematic Review and Meta-analysis

OBJECTIVES

To determine the cochlea's average size in humans and evaluate the relationships between certain covariates and cochlear size.

METHODS

A systematic search on articles on cochlear size and published in English was conducted using Cochrane, PubMed, Web of Science, and Scopus databases up to September 15, 2020. Data were pooled using random-effects with three models. The effect of demographic, clinical, and measurement-related parameters was specifically analyzed. Meta-regression and subgroup analyses were conducted. The overall effect estimation was made for outcomes.

RESULTS

The meta-analysis included 4,708 cochleae from 56 studies. The overall length of the organ of Corti was 32.94 mm (95% confidence interval [CI]: 32.51-33.38). The first and second models revealed that age, gender, country, continent, measurement method (direct, indirect), measured structure ("A" value, cochlear lateral wall), origin (in vivo, in vitro), and type (histology specimens, plastic casts, imaging) of the cochlear material did not affect the cochlear size. However, study populations (general population, patients with a cochlear implant, and patients with congenital sensorineural hearing loss [CSNHL]) were found to affect the outcomes. Compared to the other populations, patients with CSNHL had shorter cochleae. Therefore, we developed a third model and found that the general population and patients with cochlear implants did not differ in cochlear size.

CONCLUSION

This meta-analysis investigated the factors that could affect the cochlear size and found that patients with CSNHL had significantly shorter cochleae, whereas other covariates had no significant effect. Laryngoscope, 2021.

Assessment of Frequency-Place Mismatch by Flat-Panel CT and Correlation With Cochlear Implant Performance

OBJECTIVE

To calculate the frequency allocation mismatch in a group of very selected cochlear implant (CI) recipients and to contrast it with the speech perception performances.

STUDY DESIGN

Cross-sectional observational prospective study.

SETTINGS

Tertiary Audiological Department, University hospital.

PATIENTS

Fifteen adults receiving the same CI array by the same surgeon through a posterior tympanotomy, round window approach.

MAIN OUTCOME MEASURES

1) High definition flat panel computed tomography (FPCT) control of the intracochlear position of each electrode contact, and computation of the relative frequency allocation mismatch; 2) analysis of speech perception outcomes in relation with the mismatch.

RESULTS

Despite a consistent and reproducible surgical procedure with the same intracochlear array, significant deviations from the frequency allocation tables (FAT) assigned by default by the manufacturer were observed in this study.Their influences on speech perception performances were negligible in the simple tasks of words or sentences recognition in quiet (and, to a lesser extent also in noise). The greatest effect of a significant mismatch was observed for the vocal-consonant-vocal (VCV) sequences recognition under noise masking, the emotional and the linguistic prosody recognition, and the phonemes discrimination of the Auditory Speech Sound Evaluation (A§E) test.

CONCLUSIONS

The greatest frequency-to-place occurred at the high frequencies. The effect was rather irrelevant on simple words and sentences recognition, while it negatively impacted on the more complex perceptual tasks.

Cochlear Implantation With a Novel Long Straight Electrode: the Insertion Results Evaluated by Imaging and Histology in Human Temporal Bones

HYPOTHESIS

To evaluate the insertion results of a novel straight array (EVO) by detailed imaging and subsequent histology in human temporal bones (TB).

BACKGROUND

The main focuses of modern cochlear implant surgery are to prevent damage to the intracochlear structures and to preserve residual hearing. This is often achievable with new atraumatic electrode arrays in combination with meticulous surgical techniques.

METHODS

Twenty fresh-frozen TBs were implanted with the EVO. Pre- and postoperative cone beam computed tomography scans were reconstructed and fused for an artifact-free representation of the electrode. The array's vertical position was quantified in relation to the basilar membrane on basis of which trauma was classified (Grades 0-4). The basilar membrane location was modeled from previous histologic data. The TBs underwent subsequent histologic examination.

RESULTS

The EVOs were successfully inserted in all TBs. Atraumatic insertion (Grades 0-1) were accomplished in 14 of 20 TBs (70%). There were three apical translocations, and two basal translocations due to electrode bulging. One TB had multiple translocations. The sensitivity and specificity of imaging for detecting insertion trauma (Grades 2-4) was 87.5% and 97.3.0%, respectively.

CONCLUSION

Comparable insertion results as reported for other arrays were also found for the EVO. Insertion trauma can be mostly avoided with meticulous insertion techniques to prevent bulging and by limiting the insertion depth angle to 360 degrees. The image fusion technique is a reliable tool for evaluating electrode placement and is feasible for trauma grading.

Intraoperative Evaluation of Cochlear Implant Electrodes Using Mobile Cone-Beam Computed Tomography

OBJECTIVE

To evaluate the electrode status during cochlear implantation (CI) using mobile cone-beam CT (mCBCT).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral hospital.

PATIENTS

Fifty-seven patients (7 bilateral surgeries, 64 ears) who underwent CI and who received intraoperative mCBCT imaging.

INTERVENTION

CI and CBCT during surgery.

MAIN OUTCOME MEASURE

Electrode location and angular insertion depth determined by intraoperative mCBCT images.

RESULTS

There were six cases with cochlear malformation where intraoperative mCBCT was useful to confirm electrode location. Of 58 ears with a normal cochlear morphology, perimodiolar, straight, and mid-scalar electrodes were used in 30 (cochleostomy; 14 advance off-stylet technique cases), 27 (26 round window [RW] insertion, 1 extended round window [ERW] insertion), and 1 (RW insertion) ears, respectively. Complete scala-tympani (ST) insertion was achieved in 35 ears (14 cochleostomy, 21 RW or ERW insertion). The complete ST-insertion rate was significantly higher with RW or ERW insertion than that for cochleostomy insertion (p = 0.03), although cochleostomy insertion using the advanced off-stylet technique had a similar rate to RW or ERW insertion. The angular insertion depth values (average ± standard deviation) for perimodiolar electrodes (354.4 ± 29.44 degrees) were significantly smaller than those for Flex24 (464.8 ± 43.09 degrees) and Flex28 (518.2 ± 61.91 degrees) electrodes (p < 0.05).

CONCLUSIONS

Evaluation of CI electrodes using intraoperative mCBCT was comparable to that with fan-beam CT or c-arm-based CBCT. Considering the low radiation dose of mCBCT and its availability in any operation room, mCBCT is the better modality for evaluating cochlear implant electrode arrays.

Use of MRI to determine cochlear duct length in patients undergoing cochlear implantation

OBJECTIVES

It is recognised that CT can be used to determine the cochlear duct length (CDL) when selecting an electrode for cochlear implantation. It is the practice of our institution to routinely use MRI as the sole modality of pre-operative imaging in the assessment of children referred for consideration of cochlear implantation. We therefore wanted to determine whether MRI could be reliably used to determine cochlear duct length.

METHODS

An analysis of 40 ears that had undergone MRI and CT of the temporal bones was undertaken. The diameter of the basal turn was independently measured for each ear using the two modalities, and CDL was then calculated.

RESULTS

The mean error of measurement was 0.26 mm (range 0-0.8 mm), leading to a difference in calculated CDL of 0.96 mm (range 0-2.92 mm). CDL did not predict full insertion of 28 mm cochlear implant electrodes in 30 ears.

CONCLUSIONS

MRI can be used to reliably determine cochlear duct length.

Intraoperative Conebeam CT for Assessment of Intracochlear Positioning of Electrode Arrays in Adult Recipients of Cochlear Implants

BACKGROUND AND PURPOSE

Intraoperative conebeam CT has been introduced into the operating room and provides quick radiologic feedback. This study aimed to investigate its utility in the assessment of the positioning of the electrode array after cochlear implantation.

MATERIALS AND METHODS

This was a retrospective study of 51 patients (65 ears) with intraoperative imaging by conebeam CT (O-arm) after cochlear implantation between 2013 and 2017. Correct placement into the cochlea was immediately identified. Positioning assessments were later analyzed with OsiriX software.

RESULTS

Intraoperative imaging was quickly performed in all cases. No misplacement into the vestibule or semicircular canals was found. A foldover of the implanted array was identified in 1 patient. Secondary analysis by 2 raters showed excellent agreement on insertion depth angle (intraclass correlation = 0.96, P < .001) and length of insertion of the electrode array (intraclass correlation coefficient = 0.93, P = .04) measurements. The evaluation of the number of extracochlear electrodes was identical between the 2 raters in 78% of cases (Cohen κ = 0.55, P < .001). The scalar position was inconsistent between raters. When we compared O-arm and high-resolution CT images in 14 cases, the agreement was excellent for insertion depth angle (intraclass correlation coefficient = 0.97, P < .001) and insertion length (intraclass correlation coefficient = 0.98, P < .001), good for the number of extracochlear electrodes (Cohen κ = 0.63, P = .01), but moderate for the scalar position (Cohen κ = 0.59, P = .02).

CONCLUSIONS

Intraoperative conebeam CT using the O-arm is a safe, rapid, easy, and reliable procedure to immediately identify a misplacement or foldover of an electrode array. The insertion depth angle, insertion length, and number of electrodes inserted can be accurately assessed.

[Techniques and progress in the imaging of the ear]

Ear and temporal bone imaging is essential for the diagnostic and preoperative management of middle ear lesions. The scanner is the exam of choice to analyze the walls and the contents of the middle ear. MRI is used to characterize the opacities of the middle ear and to evaluate possible neurological complications. Modern imaging techniques allow intraoperative guidance in otological surgery. Hearing implants are not always a contraindication to MRI but require precautions according to the type of implant.