Home Ahead of print Instructions Contacts
About us Current issue Submit article Advertise  
Editorial board Archives Subscribe Login   


 
 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 28  |  Issue : 2  |  Page : 135-138

Preoperative and intraoperative evaluation of round window configuration during cochlear implant in children


1 Department of ENT, Indira Gandhi Institute of Medical Sciences, Patna, Bihar, India
2 Department of Paediatrics, Indira Gandhi Institute of Medical Sciences, Patna, Bihar, India

Date of Submission03-Feb-2022
Date of Acceptance24-Mar-2022
Date of Web Publication21-Sep-2022

Correspondence Address:
Dr. Rakesh Kumar Singh
Department of ENT, Indira Gandhi Institute of Medical Sciences, Sheikhpura, Patna - 800 014, Bihar
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.indianjotol_23_22

Rights and Permissions
  Abstract 


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 <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 > 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.

Keywords: Distance, pyramidal eminence, round window, vertical facial canal


How to cite this article:
Singh J, Prakash J, Mishra SK, Jha S, Singh RK. Preoperative and intraoperative evaluation of round window configuration during cochlear implant in children. Indian J Otol 2022;28:135-8

How to cite this URL:
Singh J, Prakash J, Mishra SK, Jha S, Singh RK. Preoperative and intraoperative evaluation of round window configuration during cochlear implant in children. Indian J Otol [serial online] 2022 [cited 2022 Oct 6];28:135-8. Available from: https://www.indianjotol.org/text.asp?2022/28/2/135/356449




  Introduction Top


Cochlear implants (CIs) are a well-accepted treatment for patients with severe-to-profound sensorineural hearing loss who have failed to respond to conventional hearing augmentation. In conjunction with time, tremendous refinements took place in device development and surgical techniques. One of these sophistications was to adopt round window insertion over cochleostomy. Hence, more emphasis is being placed to understand the detailed configuration of the round window and its surrounding structures. The round window membrane (RWM) is normally hidden beneath a bony overhang called the round window niche (RWN), which is formed by a posterior pillar, tegmen, and an anterior pillar.[1],[2] RWM with its niche is referred to as a round window prechamber. Prior knowledge of the topographic anatomy of a round window,[3],[4] its visibility, the direction of opening, and distances from various adjacent structures in the tympanum, are required for successful CI surgery. This knowledge can aid in decision-making before surgery and is very useful in avoiding complications such as misplacement into extracochlear sites, traumatic injury to intracochlear structures, and iatrogenic injury to surrounding structures.

The importance of imaging in the preoperative evaluation of CI recipients cannot be overstated. If the degree of associated difficulties were known before surgery, the success rate of the surgery would be high. Vaid et al. and Chemburkar formulated 10-point and 12-point scoring systems respectively based on imaging findings and calculated potential difficulty scores.[4],[5] The anatomical variations in the round window can also influence the feasibility of RWM exposure through posterior tympanotomy, and a high-resolution computed tomography scan (HRCT scan) can be used to predict the difficulty of RWM exposure. The study is being done to find if preoperative simple parameters can be used to predict the round window configuration which can help in surgical planning which will be more beneficial for less experienced surgeons in decision-making.


  Subjects and Methods Top


A prospective observational study of CI surgeries was conducted at 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 <5 years (18 boys and 12 girls) who presented to the E.N.T. OPD with prelingual deafness and were diagnosed with bilateral severe-to-profound hearing loss. Exclusion criteria were patients who had a cochlear malformation, an incomplete follow-up, explantation for any reason, postimplant major complications, device failure, or postimplant trauma. The study began after receiving approval from the institutional ethical committee with ethical clearance no 1196/IEC/IGIMS/2019.

Preoperative parameters for assessment

RadiAnt DICOM Viewer (64-bit) 2021.2 software was used to examine radiological images obtained from preoperative HRCT images of the temporal bone with a thickness of 0.5 mm in the bone window setting in an axial cut on the RWM plane displaying the basal turn of the cochlea with the RWM. The software's measurement tool was used to calculate the distance at this level of view. The distance was measured from the midpoint of the round window to the leading edge of the vertical section of the facial nerve and the pyramid.

Intraoperative parameters for assessment

All procedures were carried out by a single experienced surgeon who routinely performs CIs through the posterior tympanotomy round window approach. Following posterior tympanotomy, the RWN and membrane were identified. Recordings of the operation on a Karl Zeiss OPMI Vario S-8 microscope with a Sony recorder were used to carefully assess the visibility of the round window in every case. The visibility of the RWN during surgery is classified into three types based on the surgical view (i.e., through the posterior tympanotomy) as per the St. Thomas's Hospital classification of RWM.[7]

  • Type I = The exposure of 100% of the membrane
  • Type II = subtotal exposure and is subclassified
  • Type IIa = more than 50% but <100% of the membrane
  • Type IIb = <50% but more than 0%
  • Type III = The membrane can not be visualized at all even after the best surgical effort.


Data analysis

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). Using one-way analysis of variance (ANOVA), HRCT measurements between three different types of round window visibility were compared.


  Results Top


Round window visibility was graded as Type I found in 5 (16.67%), Type IIa found in 14 (46.67%) patients, Type IIb found in 11 (36.67%) patients, and Type III was not found in any patients [Table 1] and [Table 2].
Table 1: Comparative data of the visibility of round window with round window to vertical facial canal distance and round window to pyramid distance on high-resolution computed tomography of all patients

Click here to view
Table 2: Tabulation of grading of visibility with mean round window to vertical facial canal distance and mean distance from the round window to the pyramid and their data analysis with a 5% level of significance

Click here to view


Comparison of round window visibility with preoperative HRCT distance from round window to vertical facial canal showed the mean distance between the round window and the vertical facial canal and the round window visibility for Type I, IIa, and IIb was 5.74 ± 1.3, 4.78 ± 1.3, and 4.15 ± 1.7, respectively [Table 2].

ANOVA test showed a significant difference between three categories of round window visibility and the distance from the round window to the vertical facial canal (P = 0.033) [Figure 1] and [Table 2].
Figure 1: Histogram comparing average distance between round window to vertical facial canal on high-resolution computed tomography scan and round window for the three types of visibility. The mean distance decreases in Type IIb and Type IIa when compared to Type I

Click here to view


Comparison of round window visibility with preoperative HRCT distance from round window to pyramid showed the mean distance between round window to the pyramid and the round window visibility for Type Ia, IIa, and IIb was 5.06 ± 1.5, 4.75 ± 2.3, and 4.29 ± 0.7, respectively [Table 2]. ANOVA test showed a weak significant difference between three categories of round window visibility and distance from the round window to the pyramid (P = 0.052) [Figure 2] and [Table 2].
Figure 2: Histogram comparing the average distance between round window to pyramid on high-resolution computed tomography scan and round window for the three types of visibility, but the relationship was nonsignificant

Click here to view



  Discussion Top


CIs have transformed the management of patients with severe to profound hearing loss, allowing these patients to develop language and communicative skills comparable to peers of their age.[8] To achieve the desired result, aggressive surgical planning is required to avoid any mishaps during surgery. Hence, before surgery, adopting the soft surgical principle[9] in terms of electrode selection,[10],[11],[12] suitable insertion trajectory, and acquaintance with surgical difficulties like the distance of round window to the surrounding neurovascular structures[13],[14] will allow gaining the maximum anticipated benefit.

In this study, parameters related to topographic round window configuration were investigated to determine whether any parameter would aid in preoperative decision-making and whether any parameter could predict the visibility of the round window. A more reliable and simple distance has been calculated on preoperative HRCT to represent the round window configuration that is the distance from round window to vertical facial canal and round window to the pyramidal eminence which can help to determine whether the round window is favorable or unfavorable for insertion. This distance has the advantage of being easily estimated in the preoperative HRCT, as HRCT radiographic assessment is being done[8] in all cases while preparing for cochlear implantation. A significant difference between the three categories of round window visibility and the distance from the round window to the vertical facial canal was found (P = 0.033). If this distance is less, RW visibility will be poor which means that more drilling into the facial recess as well as RWN will be required for an adequate visualization along with modifications intraoperatively like adjustment of microscope or positioning of head more toward the surgeon to visualize posteriorly placed round window (Type IIa). While in our study round window to pyramidal eminence distance did not show any significant correlation with the round window visibility. Pendem et al.,[15] studied the round window to oval window distance and found that if this distance increases, visibility will be less while if the distance between incus short process and round window decreases, the visibility will be less.

Elzayat et al.[16] studied the round window exposure and α angle (angle between the line from the leading edge of the facial nerve on the plane midpoint of RWM and median sagittal line) and found that the α angle was smaller for complete exposure and the unexposed round window has larger angle than partial exposure group.


  Conclusion Top


As a result, HRCT measurements taken between reliable reproducible reference points in the middle ear can be used to predict round window visualization. The vertical facial canal, a definitive landmark, and the distance from the round window to the vertical facial canal can be used to identify and predict RWM visibility variations.

Acknowledgment

We thank Prof. (Dr.) N R Biswas, Director and Prof. (Dr) Manish Mandal, Medical Superintendent of the Institution for providing the hospital materials and administrative support to conduct this study. Our sincere appreciation to the patients and their relatives for their faith and support to us in this difficult pandemic period.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Mehanna AM, Abdelnaby MM, Eid M. The anatomy and anatomical variations of the round window prechamber and their implications on cochlear implantation: An anatomical, imaging, and surgical study. Int Arch Otorhinolaryngol 2020;24:e288-98.  Back to cited text no. 1
    
2.
Singla A, Gupta T, Sahni D, Gupta AK, Aggarwal A. Topography of neurovascular structures in relation to round window and how it relates to cochlear implantation. Surg Radiol Anat 2017;39:1309-16.  Back to cited text no. 2
    
3.
Atturo F, Barbara M, Rask-Andersen H. On the anatomy of the 'hook' region of the human cochlea and how it relates to cochlear implantation. Audiol Neurootol 2014;19:378-85.  Back to cited text no. 3
    
4.
Vaid S, Vaid N, Manikoth M, Zope A. Role of HRCT and MRI of the temporal bone in predicting and grading the degree of difficulty of cochlear implant surgery. Indian J Otolaryngol Head Neck Surg 2015;67:150-8.  Back to cited text no. 4
    
5.
Chemburkar VV. Predicting and grading the degree of difficulty of cochlear implant surgery by evaluating temporal bone using high resolution computed tomography and magnetic resonance imaging, Int J Res Med Sci 2019;7:3987-92.  Back to cited text no. 5
    
6.
Widmann G, Dejaco D, Luger A, Schmutzhard J. Pre- and post-operative imaging of cochlear implants: A pictorial review. Insights Imaging 2020;11:93.  Back to cited text no. 6
    
7.
Leong AC, Jiang D, Agger A, Fitzgerald-O'Connor A. Evaluation of round window accessibility to cochlear implant insertion. Eur Arch Otorhinolaryngol 2013;270:1237-42.  Back to cited text no. 7
    
8.
Liu S, Wang F, Chen P, Zuo N, Wu C, Ma J, et al. Assessment of outcomes of hearing and speech rehabilitation in children with cochlear implantation. J Otol 2019;14:57-62.  Back to cited text no. 8
    
9.
Khoza-Shangase K, Gautschi-Mills K. Exploration of factors influencing the preservation of residual hearing following cochlear implantation. S Afr J Commun Disord 2019;66:e1-7.  Back to cited text no. 9
    
10.
Wanna GB, O'Connell BP, Francis DO, Gifford RH, Hunter JB, Holder JT, et al. Predictive factors for short- and long-term hearing preservation in cochlear implantation with conventional-length electrodes. Laryngoscope 2018;128:482-9.  Back to cited text no. 10
    
11.
Venail F, Mura T, Akkari M, Mathiolon C, Menjot de Champfleur S, Piron JP, et al. Modeling of auditory neuron response thresholds with cochlear implants. Biomed Res Int 2015;2015:394687.  Back to cited text no. 11
    
12.
Fabie JE, Keller RG, Hatch JL, Holcomb MA, Camposeo EL, Lambert PR, et al. Evaluation of outcome variability associated with lateral wall, mid-scalar, and perimodiolar electrode arrays when controlling for preoperative patient characteristics. Otol Neurotol 2018;39:1122-8.  Back to cited text no. 12
    
13.
Jain S, Gaurkar S, Deshmukh PT, Khatri M, Kalambe S, Lakhotia P, et al. Applied anatomy of round window and adjacent structures of tympanum related to cochlear implantation. Braz J Otorhinolaryngol 2019;85:435-46.  Back to cited text no. 13
    
14.
Luers JC, Hüttenbrink KB, Beutner D. Surgical anatomy of the round window – Implications for cochlear implantation. Clin Otolaryngol 2018;43:417-24.  Back to cited text no. 14
    
15.
Pendem SK, Rangasami R, Arunachalam RK, Mohanarangam VS, Natarajan P. HRCT correlation with round window identification during cochlear implantation in children. J Clin Imaging Sci 2014;4:70.  Back to cited text no. 15
[PUBMED]  [Full text]  
16.
Elzayat S, Soltan I, Talaat M, Fouad YA. The role of high-resolution Computer Tomography in prediction of the round window membrane visibility and the feasibility of the round window electrode insertion. Eur Arch Otorhinolaryngol 2021;278:3283-90.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
Abstract
Introduction
Subjects and Methods
Results
Discussion
Conclusion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed96    
    Printed4    
    Emailed0    
    PDF Downloaded18    
    Comments [Add]    

Recommend this journal