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Indian Journal of Otolaryngology and Head & Neck Surgery logoLink to Indian Journal of Otolaryngology and Head & Neck Surgery
. 2023 Nov 10;76(1):944–952. doi: 10.1007/s12070-023-04333-9

Radiological Parameters Predicting the Round Window Niche Visibility through Facial Recess Approach in Cochlear Implantation

Sauradeep Das 1, Kalaiarasi Raja 2,✉, G Ramkumar 3, Vishak MS 2, Sivaraman Ganesan 4, Arun Alexander 4, Lokesh Kumar Penubarthi 4
PMCID: PMC10909018  PMID: 38440460

Abstract

Aim

The aim was to study the radiological parameters using High Resolution Computed Tomography (HRCT) temporal bone to predict the Round Window Niche (RWN) visibility through the facial recess approach and to study radiological types of the round window niche.

Materials and Methods

Prospective study was done in the patients underwent CI surgery from 2019 to 2021. HRCT radiological parameters of the patients and their intraoperative visualisation from video recordings were compared to predict the most feasible parameters to predict good visualisation of RWN.

Results

Among 51 patients (34 males, 17 females) in 48 children round window membrane insertion was done and in three children cochleostomy was done and in two children partial canal wall drilling was done due to poor visualisation of RWN area. Multiple parameters to assess the visibility of the RWN were used. Facial recess width (4.2 mm), location of the mastoid segment of facial nerve (2 mm), external auditory canal to basal turn of cochlea angle (< 13.50) and the radiological types (tunnel shape and semi-circular shape) of the RWN by HRCT were found to be significant parameters in predicting a good visualisation of the RWN.

Conclusion

HRCT parameters prepare the surgeon to face the possibility of a difficult surgery and plan to deal with difficult situations. This would eventually lead to better preparedness of surgeons for management of complications.

Keywords: Round Window Niche, Cochlear Implant, HRCT Temporal Bone, Radiological Predictors

Introduction

The global prevalence of disabling hearing loss is about 5.3% and in South East Asian countries is 4.6 to 8.8% [1]. The prevalence of hearing impairment in India is 6.3% [2]. The prevalence of congenital deafness in industrialised countries ranges from 1–3% [3]. Prelingual paediatric patients require an early intervention using cochlear implantation (CI) for better development and speech. There are various approaches for CI like posterior tympanotomy, Veria, suprameatal, endomeatal, etc. But the posterior tympanotomy approach has been found to be the most advantageous and less error prone [4]. However, there are always challenges involved in surgeries, especially in pediatric mastoid surgeries. Imaging plays a major role in CI surgery to find out any inner ear anomaly, to assess any anatomical challenges and to predict surgical complications beforehand.

All children with congenital hearing loss undergoes a High-Resolution Computer Tomography (HRCT) and Magnetic Resonance Imaging (MRI) so that the surgeons can assess anatomical features of external, middle and inner ear [5, 6]. Many parameters have been studied for better visualisation of Round Window Niche (RWN) via the posterior tympanotomy approach, especially the anatomy and angulation of the round window membrane and the RWN overhangs. These help the surgeons plan alternative techniques to face the challenges posed during the surgery. This helps to prevent unnecessary complications and a more atraumatic placement of the cochlear implant, leading to a better residual hearing for the patients [7–9].

Methodology

This prospective study was conducted in the Department of ENT from January 2019 to September 2021. Patients with bilateral sensorineural hearing loss who underwent CI surgery in the hospital were included in the study. Patients with active middle ear disease, congenital aural dysplasia, inner ear malformations patients were excluded. The sample size was calculated as 51, using the incidence of favourable sigmoid sinus line of 64% from the reference study taking confidence level of 95% and power of 80% and precision of 20% using nMaster application [10].

Institute Ethics Committee approval was obtained, HRCT images of all patients who had undergone CI surgery and video recordings of the CI surgery were studied. HRCT temporal bone was acquired Siemens CT machine 120KV and 220mA, in the axial plane as per the standard protocol in our institution: 1 mm slice thickness, 0.5 mm slice interval reconstructed in high spatial frequency algorithm in bone window. The images were viewed and measurements were made using the DICOM ((Digital Imaging and Communications in Medicine) viewing software in Centricity Universal Viewer (GE Healthcare-United States). The volume data of the images were first loaded in a multiplanar reformation (MPR) mode. True axial images were obtained by correcting the orientation of images with respect to the coronal and sagittal plane. Symmetry of internal auditory canals was used as reference for confirming the plane. In total 54 children underwent CI during the study period, three children were excluded because they had inner ear malformations like incomplete partition defects.

In HRCT, following radiological parameters were studied from the pre-operative images.

  1. Facial recess width: Perpendicular distance measured from the posterior wall of the External Auditory Canal (EAC) line to the anterolateral part of the Facial Nerve (FN), i.e., the distance between the FN and annulus (Fig. 1a).

  2. The angle between the posterior EAC wall and cochlear basal turn: The angle between the line drawn from bony-cartilaginous junction of EAC wall to tympanic annulus and second line drawn through the basal turn of the cochlea (Fig. 1b).

  3. Prediction line of Round Window Niche: It is a line drawn parallel to the posterior EAC line along the anterolateral part of the FN. Red circle represents the mastoid segment of facial nerve. Blue lines represent parallel lines along the EAC posterior border and passing along the anterolateral border of the vertical FN respectively. The place where the FN intersects the RWN gives the prediction line. Yellow line represents the line along the long axis of the basal turn of cochlea. The intersection of the prediction line and the RWM tracing is classified as anterior, middle, and posterior depending on the position of the RWM (Fig. 1c).

  4. Location of the mastoid segment of the FN: The distance of the vertical component of the FN from the line drawn along the long axis of the basal turn of the cochlea (Fig. 1c). Green line represents the distance between vertical FN and basal turn of cochlea (location of the mastoid segment of FN).

  5. Posterior canal wall/ sigmoid sinus line: A line is drawn along the posterior wall of the EAC, and a second line is drawn tangentially to the sigmoid sinus. If the basal turn of the cochlea falls between them (Fig. 2a), it is a good predictor, and if it is outside, then it is a bad predictor (Fig. 2b).

Fig. 1.

Fig. 1

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(A) Facial recess width in HRCT, (B) Angle between EAC and the Basal turn of cochlea in HRCT, (C) Red circle represents the mastoid segment of facial nerve

Fig. 2.

Fig. 2

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(A) Basal turn of cochlea lying within the posterior canal wall and sigmoid sinus line. (B) Basal turn of cochlea outside the posterior canal wall and sigmoid sinus line

  • 6.

    Jugular Bulb: The dome of the jugular bulb is typically found to be below the level of the floor of the internal auditory canal / the basal turn of the cochlea. If it lies at a higher level, the jugular bulb is considered a high jugular bulb which can obscure the view of round window niche via the posterior tympanotomy (Fig. 3a).

  • 7.

    Basal turn to the Malleo-Incudal joint: The malleoincudal joint forms an ice cream cone appearance consisting of the head of the malleus and the short process/ body of incus, which lies above the basal turn of the cochlea (Fig. 3b).

At the cochlear basal turn level, the ossicular chain is visualised as two lines, anteriorly the neck and manubrium of malleus and posteriorly the lenticular process of the incus. If the “ice cream cone” is seen at the same level as the basal turn of the cochlea, then the cochlea is turned away from its normal inferolateral axis. Thus, it could be challenging to visualize the RWN.

Fig. 3.

Fig. 3

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(A) High jugular bulb in HRCT (B) The basal turn of the cochlea to malleo-incudal joint (ice cream cone appearance of the ossicles) is at a different level indicating non rotated cochlea. (C) Anterior border of IAC to sagittal plane in HRCT

  • 8.

    Internal acoustic canal (IAC) to the sagittal plane: The IAC angle to the sagittal plane is measured. A right angle/ near right angle is favorable because in these cases, the cochlea is at a favorable angle to place the implant electrode via facial recess approach (Fig. 3c).

  • 9.

    Anterior border of the IAC angle: The two IAC are interposed from their anterior margin, and the angle between them is calculated. A parallel/close to parallel is considered favorable because, in these cases, the cochlea is at a favorable angle to place the implant electrode via facial recess approach (Fig. 4a).

  • 10.

    Basal turn and ICA angle: The angle between the basal turn of the cochlea and the Internal carotid artery (ICA) is measured. A parallel angle is considered a good parameter. The angled basal turn means the cochlea is turned away from its normal axis and may have a difficult RWN visualization (Fig. 4b).

Fig. 4.

Fig. 4

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(A) Angle between the two anterior borders of IAC in HRCT (B) Angle between IAC and Basal turn of cochlea

Radiological Types of Round Window Niche Types

The morphology of the RWN was visualised in the HRCT on a plane that had a total exposure of the round window membrane. The RWN were classified a Tunnel (Fig. 5a), Semicircle (Fig. 5b), Triangle (Fig. 5c), and Closed shapes (Fig. 5d) according to the classification by Hou et al. [11]. Based on the type of the RWN by HRCT the visibility of the RW membrane can be assessed.

Fig. 5.

Fig. 5

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Types of Round Window Niche (A) Tunnel type (B) Semicircle type (C) Triangle type (D) Closed type

Video Recording data: Intraoperative visibility of the RWN was assessed using video recordings. The visibility of the RWN were classified as (a) Invisible or nearly invisible RWN. (Fig. 6a) (b) Partially visible RWN. (Fig. 6b) (c) Fully visible RWN (Fig. 6c).

Fig. 6.

Fig. 6

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Intraoperative visualisation of RWN (A) Invisible RWN (B) Partially visible RWN (C) Completely visible RWN

Pre-operative radiological parameters were compared with the intraoperative visibility of the RWN. The radiological parameters that best predict the visibility of the RWN through the facial recess were determined.

Statistical analysis was done using IBM SPSS statistics v22.0. Continuous variables were summarized as mean with standard deviation or median with an interquartile range according to the normality tested using Kolmogorov – Smirnov test [12]. Categorical variables were summarized as frequencies with proportion. The data from all the parameters were then compared with the visibility of RWN from the video recordings. For analysis purpose video recordings were grouped as fully visible RWN in the completely visible and the partially / invisible RWN in the not completely visible groups. The receiver operating characteristic (ROC) curve was used for the continuous variables to find the cutoff value by using the Youden index for completely visible and not completely visible RWN [13]. The cut off values were then used to convert the data into categorical data. Thus, using all the categorical data, the sensitivity and specificity of each variable were calculated and compared using Chi square test. A p value of < 0.05 was considered significant. The main outcome variables of the RWN were summarized as the frequency with proportion into three groups as visible, partly visible and invisible. Continuous variables were compared across the three unpaired outcome groups using one-way ANOVA or Kruskal Wallis test based on their normality. Categorical variables were compared across the unpaired outcome groups using Chi Square test.

Results

Demographic Details

Out of 51 children, 34 were male, and 17 were female. Their ages were from 1 year to 6 years. The mean age and standard deviation for the patients was found to be 2.8 ± 1.2 years.

CI were done on the right side in 44 and on the left side in seven children. In 48 children round window membrane insertion was done and in five children cochleostomy was done due to poor visualisation of round window membrane.

Intraoperative Visualisation

Among the 51 patients, 32(62.7%) had completely visible RWN, 14(27.5%) had partially visible RWN, and 5(9.8%) had nearly invisible or completely invisible RWN. For statistical analysis purposes, we have categorised it into completely visible, which includes 32 patients and not completely visible, consisting of 19 patients.

Radiological Parameters

The facial recess width, location to mastoid segment and basal turn and ICA angle were normally distributed. The angle between posterior wall of EAC and basal turn, Anterior border of IAC angle, IAC to sagittal plane angle were non-normally distributed (Table 1).

Table 1.

Frequency of different radiological RWN types by HRCT

S.No RWN types Frequency (%)
1. Tunnel shape 16(31.8%)
2. Semicircle shape 15(29.4%)
3. Triangular shape 10(19.6%)
4. Closed type 10(19.6%)
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An intergroup normality test was done using Kolmogorov – Smirnov test to find the normally and non-normally distributed tests among the various groups. The normal continuous variables were compared with the intraoperative visibility of the RWN using ANOVA test and the non-normal continuous variables were compared using the Kruskal Wallis test. The facial recess width, Location of mastoid segment, and angle between EAC and basal turn were significant (p < .05) (Table 2).

Table 2.

Continuous variables represented by Mean ± Standard deviation or Median (interquartile range) based on normality

S.No Parameters Mean/Median Standard deviation/Interquartile range (Q3-Q1)
1. The Facial recess width (mm) 4.26 ± 0.98
2. Location to mastoid segment (mm) 1.87 ± 0.76
3. Basal turn and ICA angle (degrees) 5.84 ± 3.76
4. Angle between EAC and Basal turn (degrees) 12 21(25 − 4)
5. Anterior border of IAC angle (degrees) 173 9 (176 − 167)
6. IAC to sagittal plane angle (degrees) 86 5(89 − 84)
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ICA: Internal Carotid Artery EAC: External Auditory Canal

Using Bonferroni post hoc test, the facial recess width was significantly different between completely visible and partially visible RWN group (p < .001); Location of mastoid segment was also significantly different between the complete and partial visibility of RWN (p = .004); and Angle between EAC and basal turn was also significantly different between the completely visible and partially visible RWN (p = .029).

Categorical Variables

The categorical variables like jugular bulb, basal turn to Malleus-Incus (MI) joint, sigmoid sinus line and prediction line were used against the completely visible and the not completely visible RWN. The sensitivity and specificity of the parameters were assessed, and the p value was calculated using the Chi square test.

Jugular Bulb

A high jugular bulb was considered as a bad predictor of RWN visualisation and compared with complete and not completely visible RWN. Sensitivity of 31.6% and specificity of 78.1% were calculated, which was not statistically significant (p value = 0.515 by Fisher’s Exact test).

Basal Turn to Malleus- Incus Joint

The presence of the “ice cream cone appearance” formed by the head of malleus and the body of incus in the same plane as the cochlea’s basal turn was considered a bad predictor of the RWN visibility. But in our study, none of the patients had this finding and hence sensitivity and specificity could not be calculated for the same.

Sigmoid Sinus Line

The basal turn outside of the lines between the EAC and the tangential line to the sigmoid sinus was considered a bad predictor of the RWN visibility. Sensitivity of 52.6% and sensitivity of 59.4% were calculated. A p value of 0.405 was calculated using the Chi Square test (p = .405), which was statistically insignificant.

Prediction Line

The posterior prediction line has the highest incidence of good visualisation (Fig. 7). Hence using the posterior prediction as a good parameter against the complete and not complete visualisation; sensitivity was found to be 26.3%, and specificity was 93.8%. A p value by Fisher’s exact test was calculated to be 0.087 (p = .087), which was not statistically significant.

Fig. 7.

Fig. 7

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Distribution of intraoperative visualisation of RWN in the study population

The sensitivity, specificity, positive predictive value, and the negative predictive value of the various parameters and the p values were shown in (Table 3).

Table 3.

Continuous variables represented by Mean ± Standard deviation or Median (interquartile range) with respect to intraoperative visualisation with p values

S.No Parameters Completely visible RWN Partially visible RWN Invisible RWN p value
1. The Facial recess width (mm) 4.67 ± 0.83 3.4 ± 0.89 4.0 ± 0.25 < 0.001
2. Location to mastoid segment (mm) 2.13 ± 0.69 1.38 ± 0.72 1.6 ± 0.61 0.004
3. Basal turn and ICA angle (degrees) 5.53 ± 3.96 6.29 ± 3.77 6.6 ± 2.6 0.742
4. Angle between EAC and Basal turn (degrees) 6(20.5) 21.5(20.75) 8(13.5) 0.026
5. Anterior border of IAC (degrees) 173(8.75) 172.5(11.75) 173(7) 0.556
6. IAC to sagittal plane angle (degrees) 85.75 ± 2.88 85.64 ± 3.31 87.4 ± 1.51 0.476
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ICA: Internal Carotid Artery EAC: External Auditory Canal

Round Window Niche Types

Among the radiological types of RWN, most common was tunnel shaped (16(31.8%)) followed by triangular shape (10(19.6%)) (Table 4).

Table 4.

Sensitivity/ Specificity/ Positive Predictive Value / Negative Predictive Value and p value of continuous variables with cut off values and categorical variables

S.No Parameter (cut off) Sensitivity % Specificity% PPV% NPV% p value
1. The Facial recess width (4.2 mm) 89.5 68.8 64 91.7 < 0.001
2. Location to mastoid segment (2 mm) 89.5 53.1 53.1 89.5 0.002
3. Basal turn and ICA angle (3.5 degrees) 89.5 40.6 47.2 86.7 0.311
4. Angle between EAC and Basal turn (13.5 degrees) 78.9 53.1 50 80.9 0.019
5. Anterior border of IAC (174 degrees) 68.4 37.5 39.3 66.7 0.690
6. IAC to sagittal plane angle (87 degrees) 68.4 34.8 38.2 64.7 0.572
7. Jugular Bulb 73.7 21.9 35.9 58.3 0.743
8. Sigmoid sinus line 52.6 59.4 43.4 67.8 0.405
9. Prediction line 26.3 93.8 71.4 93.7 0.087
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ICA: Internal Carotid Artery EAC: External Auditory Canal

The RWN visibility intraoperatively and the RWN type on HRCT were compared (Fig. 8). 4 out of the 5 invisible RWN were associated with closed types of RWN in HRCT. Hence keeping the closed type as a bad predictor and the other types as good predictor a significance level of p < .001 by Fisher’s Exact test was found on comparing with completely visible and not completely visible RWN. Hence RWN type by HRCT was significant in predicting the visualisation of the RWN.

Fig. 8.

Fig. 8

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Distribution of intraoperative visualisation of RWN in the study population

Discussion

Various radiological parameters were assessed for the feasibility of the implant placement via the RWN by predicting its visibility via the posterior tympanotomy, using HRCT temporal bone. In the study, two third of the patients were male. This could be because of bias among the parents towards treating male children more in the South Indian society. There was a predisposition towards operating on the right side because of their right handedness, as patients will use the external hearing devices like phones on that side more frequently and handing of the device speech processor is easy.

In the study, focus was on the RWN visibility than the round window membrane (RWM) visibility because the RWM cannot be well visualised in the microscopic imaging intraoperatively unless the overhanging bone of the RWN is drilled. Thus, the visibility of the RWN was taken as an indirect predictor for the visibility of the RWM. Most of the patients (37 patients) were below three years of age; this showed a good awareness among the parents to seek early treatment for children with hearing disability. Based on the intraoperative findings, the RWN was divided into completely visible, partially visible, and not visible. In the present study, 62.7% of patients had completely visible, and 37.3% had incompletely visible RWN, in comparison to Xie et al. which had 53.4%, and 46.5% respectively, which is almost similar to our finding [11]. Hence, we infer that irrespective of racial difference the anatomy of RWN remains the same.

The facial recess width, location of the mastoid segment of facial nerve with respect to the basal turn of cochlea, the angle between the EAC and the basal turn, and the radiological type of the RWN were significant in predicting the visualisation of the RWN intraoperatively. Similar findings were noted in the study by Kashio et al., where posterior wall of EAC angle and the location of the mastoid segment of the FN from basal turn of cochlea were found to be significant [7]. But in their study, the facial recess width was not significant, which they contributed to the fact that a posteriorly placed RWN might not be visible in spite of a large facial recess. But Lee et al. showed all the four parameters to be significant in the visualisation of the RWN [14]. Xie et al. also concluded that these radiological parameters to be a good predictor of the intraoperative visualisation of the RWN [11]. In the present study, calibration of different parameters against the completely visible and the not completely visible RWN were studied, the sensitivity and specificity of the categorical variables were calculated. Cut off values for the continuous variables were found using ROC curves and Youden index [15]. Then they were changed to categorical variables using the cut off and compared with the completely visible and not completely visible RWN. Thus, the parameters with high sensitivity could be utilised as a screening test to identify intraoperative visualisation of the RWN during CI.

The facial recess width with a cut off of 4.2 mm (p < .001), location of the mastoid segment of FN with a cut off of 2 mm (p = .002), angle between the basal turn and the ICA with cut off of 3.5 degrees (p = .311), angle between the EAC and the basal turn with cut off of less than 13.5 degrees (p = .019), type of the RWN by HRCT where the closed type being bad predictor can be used for predicting RWN visibility.

The facial recess width is significant parameter because it is the space for the posterior tympanotomy, and if the FN is pushed anteriorly or the chorda tympani is posteriorly pushed then, the posterior tympanotomy will become smaller, and hence the space to visualise the RWN will be less. Similarly, if the FN is anteriorly placed and along the line of the basal turn of the cochlea, then it will obstruct the view of the RWN. Thus, the position of the FN is an important parameter for the feasibility of the CI via posterior tympanotomy. Considering this Hasballah et al. used the parameters linked to the vertical and horizontal segment of the FN in relation to the RWN and compared them with the posterior tympanotomy width and visibility of the RWN [16].

High jugular bulb had high sensitivity in predicting poor round window visibility in the present study, it was not statistically significant. In the study by Junior et al. the jugular bulb was shown to have a low sensitivity and was not found to be significant in assessing difficulty of CI similar to the present study [17]. Even though the jugular bulb may be highly placed it rarely affects the surgeons vision during surgery, unless it is very high enough to obscure the trajectory of electrode array and RWN.

In the present study, sigmoid sinus line was not found to be significant in predicting the visualisation of the RWN during CI. In the study by Vaid et al. it was found to be significant in predicting the difficulty of CI based on the timing of the surgery [10]. But in the study by Alam- Eldeen et al. they found that the position of the sigmoid sinus was insignificant in the visibility of the RWN during CI [18]. A similar result was obtained in the study by Park et al. [19]. An anterior placed sigmoid sinus may increase the difficulty of the mastoidectomy surgery and thus increasing the duration of the surgery, it does not hinder the view of the RWN via the posterior tympanotomy in CI surgeries. In CI surgery, there is no need for the saucerization of the entire mastoid cavity or the need for defining the entire sigmoid sinus plate completely as its position is posterior but the approach and line of view needed is anterior. The angle between the basal turn of the cochlea to the posterior wall of EAC was significant in determining the basal turn of cochlea along its normal axis or rotated abnormally. A more parallel lines (smaller degree of angle between these lines) were considered a good predictor of visibility and this had been reproduced by Kashio et al. and Lee et al. [14, 20]. Angle between the basal turn of the cochlea to the EAC line less than 13.50 was a good predictor of visibility of RWN in the present study. The angle between ICA and the basal turn of the cochlea similarly helps to determine an angulated cochlea away from its normal axis, which might have difficult implantation. Though, in the present study the test had a high sensitivity (89.5%) but it was not found to be statistically significant. A significant result with the basal turn to ICA angle was observed in predicting a poor visibility of the RWN (91%) in the study by Alam-Eldeen et al. [18].

Radiological types of the RWN could be used to predict intraoperative visualisation of the RWN. Here the closed type of the RWN type was a predictor for poor visibility of the RWN. In the tunnel/ triangular/ semicircle type of RWN, the RWN orifice to face posterolaterally and open in the oblique vertical plane. Thus, would be visible through the posterior tympanotomy. On the other hand, the closed type would have the orifice opening inferiorly and lies in a near horizontal plane to the axial plane. Thus, it would be difficult to visualise via the posterior tympanotomy. The same finding was reproduced in the study by Elzayat et al. [21].

The IAC to sagittal plane angle, Angle between the anterior margin of IAC, Sigmoid sinus line; though did not have high sensitivity or significance in our study, have been shown to be a good predictors in the study by Vaid et al. [10] This could be because Vaid et al. compared with the timing of CI rather than the visibility of the RWN as in the present study.

A posteriorly placed prediction line was a good predictor for RWN visualisation in the study conducted by Kashio et al. [20] In the present study, though the majority of the posteriorly intersecting prediction lines were predictors of good RWN visibility, but it was found to be statistically insignificant.Strengths of the study were good sample size. The study design allowed us to assess the radiological parameters. The study was performed by blinding both radiologist and analyser and by same radiologist and analyser so there were no inter-observer differences in reading the HRCT. The tests had shown results that have a good reproducibility with previous studies. A multiparametric radiological study to predict the RWN visibility were very few among the population of the Indian subcontinent and the limitation was time taken for performing the surgery which could give a real time information about the difficulty of the surgery which was not studied in the present study. This was not done because of multiple surgeons performed the CI in the study.

Conclusion

Atraumatic CI helps in the preservation of residual hearing, which may be the key to future hearing surgeries or stem cell research. Hence CI via the RW membrane is the most preferred technique. From our study radiological parameters like facial recess width, location of the mastoid segment, EAC to basal turn angle, and the radiological type of the RWN by HRCT can be used as screening tests to find out a poorly visible RWN. This prepares the surgeon for the possibility of difficult surgery, to plan and get prepared before the procedure.

Author Contribution

All the authors have equally contributed to the case report. SD and KR is the major contributor in writing the manuscript. GR and VMS participated in writing, editing and data interpretation along with SD and KR. SG,AA,LKP have commented on all the previous drafts, took part in writing and approved the article along with all the other authors.

Funding

There was no funding required to take up the study.

Data Availability

The datasets during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Ethics Approval and Consent to Participate

The study was taken after obtaining an Ethics committee approval (IEC No.: JIP/IEC/2019/213) from the Institution of Ethics Committee, JIPMER, Pondicherry, India.

Consent for Publication

Written informed consent for publication of their clinical details and/or clinical images was obtained from the patient. A copy of the consent form is available for review by the Editor of this journal.

Competing Interests

The authors declare that they have no competing interests.

Footnotes

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Citations

  1. Kashio A, Sakamoto T, Karino S, Kakigi A, Iwasaki S, Yamasoba T. 2014. Predicting Round Window Niche Visibility via the Facial Recess Using High-Resolution Computed Tomography. [DOI] [PubMed]

Data Availability Statement

The datasets during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Articles from Indian Journal of Otolaryngology and Head & Neck Surgery are provided here courtesy of Springer

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