Skeletonizing the facial nerve underwater: A pilot study

Eman Hajr; Laila Hajr; Fida Almuhawas; Farid Alzhrani; Abdulrahman Hagr

doi:10.4103/SJOH.SJOH_34_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 22 | Issue : 2 | Page : 82-85

Skeletonizing the facial nerve underwater: A pilot study

Eman Hajr¹, Laila Hajr², Fida Almuhawas³, Farid Alzhrani³, Abdulrahman Hagr³
¹ Department of Otolaryngology, College of Medicine, Imam Mohammad Ibn Saud Islamic University; King Abdullah Ear Specialist Center, King Saud University, Riyadh, Saudi Arabia
² Department of Managements Information Systems, College of Business Administration, King Saud University, Riyadh, Saudi Arabia
³ King Abdullah Ear Specialist Center, King Saud University, Riyadh, Saudi Arabia

Date of Submission	25-Jul-2020
Date of Decision	28-Jul-2020
Date of Acceptance	30-Jul-2020
Date of Web Publication	30-Dec-2020

Correspondence Address:
Dr. Eman Hajr
Department of Otolaryngology, College of Medicine, Imam Mohammad Ibn Saud Islamic University, Riyadh
Saudi Arabia

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/SJOH.SJOH_34_20

Abstract

Objective: Drilling of the facial recess represents an important step in cochlear implant (CI) surgery. It is crucial for the next step of exposing the round window. This study sought to evaluate the efficacy of underwater drilling (UWD) during the opening of the facial recess for CI surgery. Materials and Methods: This was a prospective clinical pilot study performed at a quaternary care center. We included adult and pediatric patients who underwent bilateral simultaneous CI surgeries. Any patients with facial nerve anomalies or previous ear surgery were excluded from the study. Drilling of the facial recess on one side was performed using UWD (case side); on the other side (control side), drilling was performed by minimal water drilling (MWD). Drilling was performed by the same surgeon on both sides. The time differences between the procedures were recorded. Results: A total of 21 patients were included in this study; 66% (14/21) were males, and the mean age was 8.25 years (standard deviation ± 12.00 years) at the time of surgery. UWD was completed, and the results of a normal facial nerve examination were documented postoperatively. The time needed for UWD (12 ± 6.72 min) was slightly shorter than the time needed for MWD (13 ± 6.15 min), but that difference was not significant (P = 0.71). Conclusion: The drilling of facial recess is one of the most stressful steps during CI surgery, we recommend the use of UWD because of its good safety profile and protective measures.

Keywords: Cochlear implant, facial nerve, skeletonizing

How to cite this article:
Hajr E, Hajr L, Almuhawas F, Alzhrani F, Hagr A. Skeletonizing the facial nerve underwater: A pilot study. Saudi J Otorhinolaryngol Head Neck Surg 2020;22:82-5

How to cite this URL:
Hajr E, Hajr L, Almuhawas F, Alzhrani F, Hagr A. Skeletonizing the facial nerve underwater: A pilot study. Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2020 [cited 2021 Apr 23];22:82-5. Available from: https://www.sjohns.org/text.asp?2020/22/2/82/305466

Introduction

The cochlear implant (CI) is one of the 26 greatest achievements in the medical field, 27 and CI surgery, which has been performed 28 for more than 60 years, is considered a 29 life-changing procedure for patients with 30 severe to profound hearing loss.^[1] The CI has passed through the different phases of technical developments;^[2] however, recently, there had been a paradigm shift toward performing minimally invasive CI surgery to improve different aspects of patients' experiences with the CI.

Minimally invasive CI surgery includes, but is not limited to, performing surgery under local anesthesia and allowing new candidates who are considered at high risk for morbidity or mortality with general anesthesia to undergo the procedure.^[3],[4] General anesthesia during a shorter duration 45 is preferred because of the complications 46 associated with longer anesthesia durations. With minimally invasive CI surgery, the anesthesia duration may be minimized and simultaneous bilateral CI can be offered to younger age groups.^[5] Furthermore, a smaller surgical incision can be utilized.^[6],[7] With this surgical approach comes the possibility of early fitting and activation with an external speech processor after surgery to provide the candidate with faster rehabilitation and decreased consequences that accompany delayed fitting.^[6],[8],[9]

In current practice, it is important to maintain the good safety profile of the CI. In general, CI surgery is a safe procedure; however, as with any other surgery, potential complications can occur.^{[10],[11],[12]} Surgeons should be familiar with the different complications and risk factors to ensure the optimal prevention and management.^[13] One of the feared complications is facial palsy because the facial nerve represents an important boundary of the facial recess. However, drilling of the facial recess is considered a widely acceptable maneuver during CI because it allows good visualization of the round window (RW).^[14]

In almost all cases, experienced CI surgeons have seen the positive effects of saline when opening the antrum to see the shadow of the incus earlier. However, there have been no reports of how intraoperative irrigation affects the progression of the surgical procedure.

Therefore, this study sought to evaluate the efficacy of underwater drilling (UWD) with the use of copious amounts of irrigation during facial recess drilling for CI surgery.

Materials and Methods

This prospective pilot study was performed at a quaternary center. The Internal Review Board reviewed and approved the study protocol involving human participants. The study was performed in accordance with the tenets of the declaration of Helsinki. The inclusion criteria were severe to profound sensorineural hearing loss; fulfillment of the indications for a CI; and acceptance by the CI committee to undergo bilateral simultaneous CI. Participants were excluded if there was evidence of facial nerve anomalies found during the preoperative imaging study and those who had facial weakness. We also excluded patients with a history of ear surgery and those who underwent sequential implantation for any cause. Before the date of surgery, either the patients or their legal guardians provided written informed consent for their participation in our study.

Setting and procedures

All surgeries were performed using same minimal approach that was explained previously.^[6] All surgeries were performed under general anesthesia. With the minimally invasive approach, the postauricular area was prepared with povidone-based solution and a local anesthetic agent composed of 1% lidocaine mixed with 1:100,000 of epinephrine was administered. A facial nerve monitor was used intraoperatively for all cases. The surgical incision was limited to 3 cm in length and approximately 1 cm away from both the mastoid tip inferiorly and hairline superiorly; therefore, no hair shaving was performed for any candidate. The posterosuperior flap was elevated to make a pocket that could house the receiver stimulator and to secure the device in the tight periosteum pocket with good pressure without the need for additional suturing. This study was novel because of the use of UWD drilling during the facial recess step on one side (case side) and minimal water drilling (MWD) on the other side (control side) of the same patient by the same surgeon.

After completing cortical mastoidectomy in the UWD group, the time during which the short process of the incus was identified, documented in small paper slip by the circulating nurse as time A (time required to identify the incus with UWD). The surgeon continued drilling over the margin of the facial nerve. The drill was held with the dominant hand while the other hand held the suction tip barely touching the mastoid cavity to keep it full of saline. This was performed during the entire drilling process until the pyramid and stapedial tendon were identified as the landmarks of the RW. The circulating nurse was then informed to record time B (time required to identify the pyramid with UWD). Thereafter, the other surgical steps were completed as usual.

On the control side, the same initial steps were performed; then, drilling of the facial recess using MWD was performed. During MWD, the surgeon held the drill with the dominant hand; beside it, he held the suction tip with the nondominant hand. With this method, the amount of irrigation inside the mastoid cavity was minimal, and the surgeon had to depend on visual identification of the facial nerve without the magnification allowed by the water. The recording of the identification times were the same: time C (time required to identify the incus with MWD) and time D (time required to identify the pyramid with MWD). The slip of paper was handed to the research team. No one from the team was involved in the surgical steps. The time required to complete the facial recess drilling steps was calculated as the difference between the time required to identify the pyramid and the time required to identify the incus as follows: time B – time A for UWD and time D – time C for MWD.

The side on which the procedure was started and whether to use UWD or MWD first were completely dependent on the preference of the surgeon. The surgeons were advised at the beginning of the study that they could vary their choices during each case. Facial recess drilling was performed on both sides by the same surgeon who was either an otology consultant level or a 2^nd-year fellow in training.

Statistical methods

Skewness and kurtosis tests were used to determine the normal distribution of continuous variables. Frequencies and percentages were used to summarize the categorical variables. Descriptive statistics, including the mean and standard deviation (SD), were used for the continuous variables. The Chi-square test (or Fisher's exact test, as appropriate) was used for categorical data. Student's t-test (or Mann–Whitney U-test, as appropriate) was used for the continuous variables. Data were analyzed using R Studio software version 3.2.4 (developed by thwe R Core Team, R Foundation for Statistical Computing, Vienna, Austria) and MedCalc software version 14.8.1 (developed by MedCalc Software bv, Ostend, Belgium). Statistical significance was considered when P < 0.05.

Results

A total of 21 patients were included in this study; 66% (14/21) were male and the mean age was 8.25 years (±SD 12.00 years) at the time of surgery. The youngest patient was 1-year-old, and the oldest was 56 years old.

The surgeon chose to start with right ear for 14 out of 21 patients. Of those 14 patients, UWD was performed first in 8. This choice did not result in a significant difference between MWD and UWD (P = 0.874) [Table 1]. UWD was completed without complications for all candidates. None of the patients exhibited facial nerve weakness in either side postoperatively. The time required for UWD (12 ± 6.72 min) was slightly shorter than that required for MWD (13 ± 6.15 min), but that difference was not significant (P = 0.71) [Figure 1].

Table 1: Distribution of cases according to the starting side

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Figure 1: Total time required for facial recess drilling using underwater drilling and minimal water drilling

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Otology fellows were more involved in the facial recess drilling process. Seventeen procedures were completed bilaterally by fellows, and only four procedures were performed by consultants.

Otology fellows required approximately 13.17 ± 7.33 min to perform UWD; however, consultants required 8.5 ± 2.38 min. This difference was not significant (P = 0.2311) [Table 2].

Table 2: Surgeon level and surgical time for the two techniques

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Discussion

This study provides the first preliminary evidence of the advantages of UWD with copious amounts of irrigation during facial recess drilling for CI surgery. In this study, UWD was completed without complications for all patients. All patients had normal facial nerve function postoperatively. It was interesting that the UWD consumed shorter time although it is new technique to the participated surgeons. The interesting point in that group is the shorter time with UWD although it is new technique to the participated surgeons.

In the literature, the incidence of facial nerve palsy was approximately 0.7%, but it is still considered a major complication of any CI surgery.^{[15],[16],[17]} This complication, which can occur immediately after surgery or later, is catastrophic to both the patient and the surgeon because of different functional, emotional, and medico-legal concerns,^{[18],[19],[20]} and every effort should be exerted to avoid this complication. The mechanism of facial palsy is variable, but thermal damage is an important mechanism that can result in edema of the nerve sheet secondary to vasodilatation.^[15] However, the drilling process is always combined with water irrigation to wash away dust and provide a cooling effect on the drilled area. With copious amounts of irrigation, the heat generation can be lowered. It is unknown whether the cooling effect is the only advantage or if there are any other advantages with the use of irrigation during the drilling process.

Every material has a precise light transmission and reflection characteristic. When looking at underwater object light refraction from the surface, a “virtual” image seems to appear at a shallower depth. The result of light refraction is often observed in everyday life. A common example is the illusion of a fish at a shallow depth of water when observed from the surface of a pond.^[21] Furthermore, any clear fluid will act like a lens as long as the bottom and top surfaces are not parallel.^[22] In an open mastoid, there are multiple areas with irregular surfaces because every ear has distinctive pneumatization patterns; therefore, filling it with water will produce the lens effect. As a result, the eyes and brain will see a picture that is different from the actual object. This may explain the effect of UWD in this study.

This study had some potential limitations. First, the sample size was small. This may have affected the difference in times required to perform the two techniques because the new technique requires learning time and theoretically less use of the facial nerve probe. Second, we did not include postoperative feedback from the surgeons who participated in the study. However, because UWD was not used before this study, further investigations of this technique are necessary.

Conclusion

Being one of the largest otology center we believe that our role exceeded the direct medical services to be part of innovation and inventions for the best quality of life with CI, hence achieving good safety profile with UWD could lead us to utilize such technique for more cases. Aiming to provide the surgeon with good adjunctive measures for one of the most stressful step in CI surgery.

Acknowledgment

The author would like to thank the Saudi ORL society for recommending this research project.

Financial support and sponsorship

Nil.

Conflicts of interest.

There are no conflicts of interest.

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