Round Window Visibility Research Articles

Prediction of difficult round window visibility during cochlear implantation via a reformatted CT facial recess view: A retrospective study with surgical correlation.

Cochlear implant surgery is performed commonly through the facial recess via the round window (RW) approach. This study aims to evaluate the utility of reformatting the pre-operative CT temporal bone scan into a CT facial recess view in alerting surgeons to a potentially difficult surgery with poorly visualized round window. This is a retrospective study of 41 patients (43 ears), who had undergone cochlear implant surgery. Intraoperative findings of round window position relative to 2nd genu-mastoid portion of facial nerve, and round window membrane orientation were recorded by the surgeons. Pre-operative CTs were analyzed by two radiologists in axial and a reformatted facial recess plane that simulates the surgeon's view via the facial recess. Radiological assessment markers include the facial nerve-chorda tympani nerve width (FN-CTN) measured 1.2mm inferior to the exit point of the chorda tympani nerve into the tympanic cavity, round window position relative to 2nd genu-mastoid segment of the facial nerve and RW membrane's angle from the vertical axis. The best predictor for difficult round window intraoperative visibility is the RW position relative to the 2nd genu-mastoid segment of the facial nerve lying lateral to it on CT facial recess reformatted images. A RW that lies partially to completely posterior to the posterior border of the 2nd genu-mastoid segment of the facial nerve had up to 55.6% risk of encountering difficult access, while those positioned anterior to or partially anterior to the anterior edge of the 2nd genu-mastoid segment of the facial nerve had 0% risk of difficult access (p<0.05). There are substantial agreements in the intra-rater (Kappa=0.751, p<0.001) and inter-rater reliability (Kappa= 0.698, p<0.001). There is no significant association between surgical difficulty and facial nerve-chorda tympani distance or RW angle (p>0.05). Identification of round window positions in the reformatted CT facial recess view is a useful tool in predicting potentially difficult round window access in cochlear implant surgery. RW= Round window, FN-CTN= facial nerve to chorda tympani nerve width.

Objective evaluation, using computed tomography, of round window access for cochlear implantation.

The aim of this study was to determine optimal radiological parameters for assessment of the round window approach in cochlear implantation surgery. Patients undergoing cochlear implantation at the Department of Otolaryngology in Szczecin, between 2015 and 2022 inclusive, were eligible for the study. Radiological assessments were performed according to eight parameters (seven proposed in the literature) and visibility clinical assessments were made intra-operatively on a scale of 1 to 5 (1 - not visible, 5 - fully visible). Visibility assessments of the round window niche (RWN) and round window membrane (RWM) allowed the difference (RWN minus RWM) to be used as a clinical assessment of the size of the overhang over the round window. Computed tomography images of 57 ears from 52 patients were analyzed in terms of round window access. The study group included 26 females and 26 males, ranging in age from 1 year to 80 years, with a median age of 41 years. In clinical assessment, round window visibility was rated as 5, after removal of the bone overhang, in 69% of patients. Cochlear access through the round window was achieved in 39 (68%) cases, extended access through the round window in 13 (23%) cases and cochleostomy was performed in 5 (9%) cases. Statistically significant ordinal correlations with round-window access were found using one parameter from the literature (Chen_Angle) and from our proposal (RWM_prediction). From parameters describing the bone overhang of the round window, positive correlations (using Kendall rank tests) were found using parameters from the literature (Sarafraz_OH and Mehanna_OH). Radiological measurements describing access to the round window which determine the angle based on the anatomy of the posterior wall of the auditory canal and the position of the facial nerve were found to be of the highest value. In the future, the use of algorithms for computed tomography evaluation and robot-assisted surgery will require parameters for assessing round window access, for surgery planning and choice of electrode. The parameters proposed by various authors are summarized, allowing researchers to assess their usefulness in further clinical practice.

Round Window Visibility in Cochlear Implantation : Pre-operative Prediction Using Various Radiological Parameters.

The round window approach has become the most preferred route for electrode insertion in cochlear implant surgery; however, it is not possible at times due to difficult round window membrane (RWM) visibility. Our study aims to investigate the relationship between preoperative radiological parameters and the surgical visibility of the RWM in Cochlear implant patients. A prospective cross-sectional study of 31 patients, age < 6 years, with bilateral severe to profound sensorineural hearing loss was conducted at a tertiary care hospital. The preoperative HRCT temporal bone scan was studied, and the parameters evaluated were facial nerve location, facial recess width, and RWM visibility prediction. All patients were operated on via the posterior tympanotomy. The surgical RWM visibility was done after optimal drilling of the posterior tympanotomy recess. The relationship between the radiological parameters and surgical visibility of RWM was evaluated. The difference in the facial nerve location as per the type of RWM was found to be significant (p value < 0.05). However, the facial recess width was not significantly associated with RWM visibility. The radiological prediction of RWM visibility by tracing the prediction line over RWM was significantly associated with intraoperative RWM visibility. The goal to look for preoperative scans is to predict the ease or difficulty of RWM visibility during surgery. The difficult visualization of the RWM, can result in dire intraoperative consequences. A comprehensive understanding of preoperative radiological parameters, coupled with meticulous surgical planning, is crucial to address these challenges effectively by focusing on enhancing RWM visualization.

The feasibility of cochlear implantation in early infancy

To determine the key image anatomical parameters that are relevant to cochlear implantation (CI) using temporal bone high-resolution computed tomography (HRCT) scans and to identify age group differences in order to provide image anatomical support for early CI. The data of 346 temporal bone HRCTs of 173 children from 5 months to 18 years of age were retrospectively selected and reviewed. Parameters of the human temporal bone that are relevant to CI key surgical steps include mastoid thickness (MT), the facial recess width (FRW), and an angle representing the round window visibility. All measurements are performed on axial images. There was no significant difference in the above morphological values by gender (p>0,05). Two-sided FRW was not significantly different (p>0,05), but MT and angle A were significantly different (p<0,001). FRW and angle were independent of age (p>0,05). However, MT had been found to exhibit postnatal development. The linear function of MT were calculated as y=2463 × group(s)+20,574 (p<0,001). Based on preoperative imaging analysis at different ages, middle ear development was stable at 5 months of age, allowing early CI in infancy with severe to severe hearing loss at this age. These data must be considered exploratory and more extensive clinical studies are needed.

A modified form of the St Thomas' Hospital (STH) classification to improve cochlear implantation outcomes.

re-evaluation and modification of the St Thomas' Hospital (STH) classification to improve cochlear implantation outcomes. STUDY DEIGN: a prospective cohort study. children (n=20) between 2 to 8 years old who received a unilateral cochlear implant, all had difficult round window visibility and/or accessibility for electrode insertion. 10 had a round window insertion through the endoscopic assisted cochlear implantation and the remaining 10 had the same insertion using the retro-facial approach. THE SURGERY: two alternative techniques were used to overcome the difficult cases of round window electrode insertion: 1Endoscopic assisted cochlear implantation 2Transmastoid retro-facial approach RESULTS: both techniques proved to be effective and practical to overcome cases with difficult round window visibility and/or accessibility for electrode insertion. Round window insertion is associated with superior cochlear implantation outcomes, so we recommend a new modification to the STH classification to bypass the cochleostomy insertion.

Excursus in Chorda-Facial Angle Variation in Cochlear Implant Surgery: Cadaveric Temporal Bone Study.

Facial recess approach through posterior tympanotomy is the most common & best appraoch for facilitating Cochlear Implant surgery through the round window. Sacrificing Chorda tympani nerve can be avoided by proper understanding of the anatomy of the Facial Recess & Chorda-Facial angles. Hence it is important to know the Chorda-Facial angle to prevent injury in Facial recess approach during Cochlear Implant surgery. Objective This study is done to know the Chorda-Facial angle variation with Round Window visibility during the Facial recess approach which is of relevance in Cochlear Implant surgery. Methods Thirty adult normal wet human cadaveric temporal bones were studied by performing by Posterior Tympanotomy & Facial Recess approach by using ZEISS microscope. Photographs were taken by digital camera of 26 megapixel, imported into computer, then Chorda-Facial angle were measured by Digimizer software & mean angle was calculated. Results The mean angle between the facial nerve & chorda tympani nerve was 20.232°. Bifurcation of chorda tympani nerve at the level of origin itself from the vertical segment of facial nerve was found in 6 Temporal bones out of 30. Round window visibility was noted in all 30 temporal bone specimens (100%). Conclusion The wide Chorda-Facial angle variations, especially the narrowest angle should be known to the otologist in particular to the Cochlear Implant surgeon, which may help avoid inadvertent damage to the CTN in facial recess approach during Cochlear Implant surgery & use diamond burr size of 0.6mm or 0.8mm.

Preoperative and Intraoperative Evaluation of Round Window Configuration during Cochlear Implant in Children

Context: To establish a reliable factor for predicting the anticipated difficulty and adequacy of niche drilling without damaging the intracochlear structures during cochlear implant (CI) surgery. Aims: This study aimed to access the correlation of the distance from round window-to-vertical facial canal and round window to pyramid with the visibility of round window intraoperatively. Settings and Design: A prospective observational study of CI surgeries was conducted in the E.N.T. Department of Indira Gandhi Institute of Medical Sciences, Patna, from December 2019 to December 2021. The study included 30 children aged &lt;5 years who presented to the E.N.T. OPD with prelingual deafness and were diagnosed with bilateral severe-to-profound hearing loss. Subjects and Methods: The preoperative high-resolution computed tomography images in the axial cut bone window setting at round window level were used to calculate the distance of round window-to-vertical facial canal and round window to pyramid on the RadiAnt DICOM Viewer. The intraoperative visibility was assessed through the recordings of the operation. Statistical Analysis Used: The data were analyzed using the MS Office 2019 Excel spreadsheet (Microsoft Corp., Redmond, WA, USA) and the program IBM SPSS 28.0.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance was used. Results: A significant difference existed between round window and vertical facial canal distance measured preoperatively with the three categories of visibility of round window intraoperatively (P = 0.033), but a weak significant difference was found with the distance of round window to the pyramid with the visibility of round window (P &gt; 0.05). Conclusions: Preoperative computed tomography measurement of the round window and vertical facial canal is a reliable predictor of a round window configuration that may aid in predicting the round window visibility.

Dimensions of the Posterior Tympanotomy and Round Window Visibility Through the Facial Recess: Cadaveric Temporal Bone Study Using a Novel Digital Microscope.

To measure the width of the posterior tympanotomy in cadaveric temporal bones using the digital microscope and classify the round window visibility through it. In 17 cadaveric wet adult temporal bones, cortical mastoidectomy followed by posterior tympanotomy was performed, delineating the facial and chorda tympani nerves. Antero-posterior width of the facial recess was measured at the levels of oval window and round window with the help of a digital microscope and its software. Visibility of the round window through the facial recess was assessed and classified according to the St. Thomas Hospital classification. The mean antero-posterior width of the facial recess measured was 4.7 ± 0.6mm at the level of oval window and 4.3 ± 0.7mm at the level of round window. Round window visibility grading in bones studied were as follows-Type 1 (53%), Type 2a (24%), Type 2b (18%) and Type 3 (5%). Interobserver variability of the posterior tympanotomy measurements using the digital microscope was found to be 91.1% with a 95% confidence interval of 79 to 97% at the level of oval window and 94.1% with a 95% confidence interval (CI) of 87 to 98% at the level of round window. The visibility of the round window is not entirely dependent on the facial recess width at the round window level, suggesting that other factors like cochlear rotation may also contribute to its actual location. Measurements of micro distances with the help of digital microscope seems to be convenient, cost effective and accurate with good inter observer reliability.

Effect of Sigmoid Sinus Position on the Difficulty and Approaches to Cochlear Implantation Surgery.

To assess the effect of the position of the SS on CI regarding the ability to perform posterior tympanotomy, round window visibility, and mastoid pneumatization. This is a prospective study, including 65 adult patients with CI performed at our center during 2017. We used 3 methods to assess SS position using a computed tomography (CT) scan. Lee's line passing through the tympanic segment of the facial nerve. Park's line passing through the facial nerve and round window membrane. Our proposed method using a parallel line from the external auditory canal and passing through the facial nerve. Relation to mastoid pneumatization on CT and to intraoperative round window visibility were assessed in relation to intraoperative position of the SS. The method by Park et al. was statistically significant (p<0.001); however, a cutoff point could not be set. Lee's method was statistically insignificant (p=0.091). Our proposed method was statistically significant with a cutoff point at ≤2.46 mm (p=0.001). SS position did not affect pneumatization nor round window visibility. The position of SS preoperatively using a CT might suggest the inability to perform posterior tympanotomy and the need to change side or approach. However, it does not affect neither mastoid pneumatization nor visibility of the round window niche through the facial recess.

Radiological and surgical aspects of round window visibility during cochlear implantation: a retrospective analysis

PurposeThe round window approach has become the most preferred option for cochlear implant (CI) insertion, however, sometimes it may not be possible due to the (in)visibility of the round window membrane (RWM). We addressed the prevalence, consequences and indicators of difficult detection of the RWM in cochlear implant surgery.MethodsThis study retrospectively analysed the operative reports and preoperative high resolution axial-computed tomography (CT) scans of a consecutive cohort of patients who underwent a CI insertion. The main outcomes were surgical outcomes of the RW approach, and assessment of radiological markers.ResultsThe operative reports showed that RWM insertion was feasible in 151 out of 153 patients. In 18% of the patients the RWM was difficult to visualize. All these patients had at least one intraoperative event. The chorda tympani nerve (CTN) or posterior canal wall was affected in 8% of the 153 patients and the fallopian canal in 6%. These patients had a facial-chorda tympani nerve distance on the CT scan that was considerably smaller than normal patients (1.5 mm vs 2.3 mm). In addition, a prediction line towards the anterolateral side of the RWM was found to be more prevalent in these patients’ CT scans (sensitivity 81%, specificity 63%).ConclusionThe RW approach is feasible in almost all patients undergoing CI surgery. Difficult visualisation of the RWM seems to lead to at least one intraoperative event. Radiological measures showed that these patients had a smaller facial recess and a more anteriorly placed facial nerve, which can be used to better plan a safe insertion approach.

Combined preoperative HRCT parameters for prediction of round window visibility in pediatric cochlear implant patient

ObjectiveTo evaluate the add value of combined analysis of high resolution computed tomography (HRCT) temporal bone parameters in accurate prediction of round window (RW) visibility through posterior tympanotomy. Patients and methodsa retrospective observational study was held in a tertiary center, conducted on 45 cochlear implant pediatric candidates between January 2017 and September 2019. Candidates were referred for CT temporal bone. They were classified into fully visible RW cases and partially or non-visible RW cases. Radiological measurements were compared between the two groups for prediction of RW visibility separate and in combination. Results45 patients were included in the study (26 males (57.8%) and 19 females (42.2%)). Their median age was 4 years (2–12 years). There were 38 (84.4%) fully visible and 7 (15.6%) partially or non-visible RW cases. Kashio posterior line (n:32/3), fascial recess width (FRW) (mean: 4.9 (3.5–7.5)/4.2 (4–4.7) mm) and round window location (RWL) (3 (1–4)/2.8 (1–3)mm) measurements significantly differentiated between the two groups; (P value 0.034, 0.012 & 0.025 respectively). Posterior kashio line and cut off values of ≥4.75 mm of FRW & 2.95 mm of RWL were showed sensitivity 84.2%, 63.2% & 65.8%, and accuracy 80%, 68.9% &68.9% in prediction of RW visibility respectively. Combination of Kashio prediction line with cut off value ≥ 7.45 mm (sum of FRW & RWL) showed P value 0.003 with further improve in the sensitivity and overall accuracy in prediction of RW visibility from 84.2% to 80% up to 91.4% and 88.6% respectively. Conclusioncombined parameters using Kashio line with FRW and RWL increases sensitivity and overall accuracy in prediction of RW visibility rather than single parameter.

Predicting round window visibility by HRCT during cochlear implantation in children

Objective: The present study aimed to radiologically evaluate the visibility of round window during cochlear implantation by high-resolution computed tomography (HRCT) imaging of temporal bone. Study design: This was a cross-sectional descriptive analytic study. Methods: Two new radiologic measurements were evaluated on the presurgical HRCT of temporal bone, including (1) the angle between the line parallel to coronal axis that passes through the middle of the round window niche (RWN) and the line that connects the anterior portion of facial nerve (FN) to the middle of the RWN (RWN angle) and (2) the vertical distance between this coronal plane and the anterior portion of the FN, modified facial recess distance (MFRD). The measurements were then compared with the visibility of the round window (RW) during operation, as reported by the surgeon. Result: The present study compared the abovementioned CT scan findings of cochlear implanted children in visible (n = 21) and nearly invisible (n = 21) RW during surgery, as reported by the surgeon. The analysis revealed that both MFRD (P < 0.01) and RWN angle (P < 0.04) were significantly different between the two groups. Conclusion: the RWN angle and MFRD are fairly reliable predictors of round window visibility during cochlear implantation.

Anatomical Correlates and Surgical Considerations for Localized Therapeutic Hypothermia Application in Cochlear Implantation Surgery.

Hypothesis:Application of localized, mild therapeutic hypothermia during cochlear implantation (CI) surgery is feasible for residual hearing preservation.Background:CI surgery often results in a loss of residual hearing. In preclinical studies, local application of controlled, mild therapeutic hypothermia has shown promising results as a hearing preservation strategy. This study investigated a suitable surgical approach to deliver local hypothermia in patients utilizing anatomical and radiologic measurements and experimental measurements from cadaveric human temporal bones.Methods:Ten human cadaveric temporal bones were scanned with micro-computed tomography and anatomical features and measurements predicting round window (RW) visibility were characterized. For each bone, the standard facial recess and myringotomy approaches for delivery of hypothermia were developed. The St. Thomas Hospital (STH) classification was used to record degree of RW visibility with and without placement of custom hypothermia probe. Therapeutic hypothermia was delivered through both approaches and temperatures recorded at the RW, RW niche, over the lateral semicircular canal and the supero-lateral mastoid edge.Results:The average facial recess area was 13.87 ± 5.52 mm2. The introduction of the cooling probe through either approach did not impede visualization of the RW or cochleostomy as determined by STH grading. The average temperatures at RW using the FR approach reduced by 4.57 ± 1.68 °C for RW, while using the myringotomy approach reduced by 4.11 ± 0.98 °C for RW.Conclusion:Local application of therapeutic hypothermia is clinically feasible both through the facial recess and myringotomy approaches without limiting optimal surgical visualization.

Anatomical Study of the Facial Recess with Implications in Round Window Visibility for Cochlear Implantation: Personal Observations and Review of the Literature.

Introduction Posterior tympanotomy through facial recess (FR) is the conventional and most preferred approach to facilitate cochlear implantation, especially when the electrode is inserted through the round window. The complications of the FR approach can be minimized by proper understanding of the anatomy of the FR. Objective The present study was undertaken to assess the various parameters of FR and round window visibility, which may be of relevance for cochlear implant surgery. Methods Thirty-five normal wet human cadaveric temporal bones were studied by dissection for anatomy of FR and posterior tympanum. Photographs were taken with an 18 megapixels digital camera, which were then imported to a computer to determine various parameters. Results The mean distance from the take-off point/crotch of the chorda tympani nerve (CTN) to the stylomastoid foramen was 4.08 ± 0.8 mm (range of 2.06 - 5.5 mm). The variations in the course of the CTN included origin at the level of the lateral semicircular canal. The mean chorda-facial angle in our study was 26.91° ± 1.19°, with a range of 25° to 28.69°. The mean FR length ranged between 9.4 mm and 18.56 mm (mean of 12.41 ± 2.91mm) and varied with the origin of the CTN and pneumatization of temporal bone. The average maximum width of the FR was 2.93 ± 0.4 mm (range 2.24–3.45 mm) and the mean width of the FR at the level of the round window was 2.65 ± 0.41 mm. Conclusion The FR approach provides good access to the round window membrane in all cases. In some cases, table adjustment is required.

Lateral Rotation of the Basal Turn of the Cochlea with its Impact on Cochlear Implant Feasibility

AbstractPurpose: To investigate variation in cochlear orientation, with respect to rotation of basal turn, and its implication to cochlear implantation.Methods: Prospective observational study including 25 patients that underwent cochlear implantation at Tanta Cochlear Implant Centre (TCIC), Otolaryngology, Head & Neck Surgery (ORL-HNS) Department, Faculty of Medicine, Tanta Univer-sity, that had been done from April 2015 to December 2015, with available charts including Computerized Tomography (C.T.) scan of temporal bone. Axial cut with maximum visu-alization of the round window was identified, then angle of axial rotation of the cochlea was measured using two methods: Angle 1 between the midline and line through the long axis of the basal turn and angle 2 between the long axis of the basal turn and the long axis of horizontal segment of Internal Carotid Artery (I.C.A.) at the same axial level. All angles were measured using computer software. All cases had cochlear implantation using standard trans-mastoid technique. Round window visibility through facial recess was assessed after maximal widening of the facial recess to achieve best exposure. Then, cases were assigned into one of two groups according to the degree of round window visibility, Group I: Case with full exposed Round Window (R.W.) membrane. Group II: Cases with partially exposed R.W. membrane or invisible R.W. membrane.Results: Following review of the Computed Tomography (CT) images of the two patients (Group II) in whom cochlear implant was difficult. It appeared that the orientation of the basal turn of the cochlea relative to the midline (angle 1) was more obtuse or more acute than in other patients with p- value =0.007 & 0.002 respectively. It also showed that the orientation of the basal turn of the cochlear in relation to long axis of horizontal part of internal carotid artery (angle 2) was more obtuse relative to other patient with p-value=0.002 & 0.001 respectively.Conclusion: Our work highlights the importance of pre-operative measuring basal turn angel relative to fixed plane, as the mid-sagittal plane in pre-operative CT, instead of other anatomical structure that could be subjected to developmental remodeling and its impact on surgery of cochlear implantation.

Role of Multislice CT Imaging in Predicting the Visibility of the Round Window in Pediatric Cochlear Implantation.

High-resolution computed tomography (HRCT) magnifies the role of preoperative imaging for detailed inner and middle ear anatomical information and enhances more efforts for better dependent correlation and measurements of round window (RW). To find an applicable way by HRCT imaging for the prediction of the visibility of the RW during cochlear implantation (CI) surgery. Five radiologic measurements were performed on the axial HRCT and these measurements were correlated with the degree of RW visibility after performing posterior tympanotomy during CI surgery. Sixty ears of 60 children were included in the current study. A significant correlation was found between the degree of RW visibility and the following: 1) the angle between RW, facial nerve (FN), and the coronal axis (p < 0.00001); 2) the vertical distance between RW and FN (p = 0.006552); and 3) FN location to the axis of cochlea (p = 0.000419). On the other hand, nonsignificant correlation was found between the degree of RW visibility and both of the facial recess width and the angle between axis of cochlea and external auditory canal (p = 0.941363 and p = 0.59036 respectively). The angle between RW, FN, and the coronal axis and the vertical distance between RW and FN are proportionate with the degree of surgical RW visibility in children during CI. In children, surgeons can depend on those two parameters in addition to the distance between FN location to the axis of cochlea in predicting the RW visibility rather than depending on the measurements related to the external auditory canal.

Prediction of round window visibility in cochlear implantation with temporal bone high resolution computed tomography

Objective: To discuss the prediction of round window(RW) visibility in cochlear implantation(CI) with temporal bone high resolution computed tomography(HRCT). Methods: From January 2013 to January 2017, 130 cases underwent both HRCT and CI in our hospital were analyzed. The distance from facial nerve to posterior canal wall(FWD), the angle between facial nerve and inner margin of round window(FRA), and the angle between facial nerve and tympanic anulus to inner margin of round window(FRAA) were detected at the level of round window on axial temporal bone HRCT. A line parallel to the posterior wall of ear canal was drawn from the anterior wall of facial nerve at the level of round window on axial temporal bone HRCT and its relationship with round window was detected (facial-round window line, FRL): type0-posterior to the round window, type1-between the round window, type2-anterior to the round window. Their(FWD, FRA, FRAA, FRL) relationships with intra-operative round window visibility were analyzed by SPSS 17.0 software. Results: FWD(F=18.76, P=0.00), FRA(F=34.57, P=0.00), FRAA (F=14.24, P=0.00) could affect the intra-operative RW visibility significantly. RW could be exposed completely during CI when preoperative HRCT showing type0 FRL. RW might be partly exposed and not exposed when preoperative HRCT showing type1 and type2 FRL respectively. Conclusion: FWD, FRA, FRAA and FRL of temporal bone HRCT can predict intra-operative round window visibility effectively in CI surgery.