Underwater endoscopic ear surgery for repair of lateral semicircular canal fistulae secondary to cholesteatoma—a pilot safety analysis

Introduction

The management of labyrinthine fistulas has been a subject of debate in the literature for years. The original microscopic approach involved leaving the matrix over the fistula without opening the labyrinth to preserve the existing hearing function. This method may leave a potential source of ongoing bone erosion and delayed sensorineural hearing loss (1-3). Another approach is complete removal of the matrix. This often, but not always, involves a canal wall down mastoidectomy approach in which the posterior canal wall is drilled away to create a wider surgical field (1,4,5). Sometimes the fistula is treated during a second staged procedure 6–12 months later to preserve the cochlear function, although it has been shown that both one- or two-staged techniques are equally likely to preserve hearing (6,7).

There have also been differing opinions regarding repair options. Some authors prefer occlusion or plugging of the canal, while others advocate for resurfacing. Occlusion is associated with a higher success rate and lower recurrence of symptoms, offering a water tight seal while compressing the membranous labyrinthine in the process, however, the method is invasive and risks sensorineural hearing loss (8-11). Resurfacing of the canal, using materials such as a cartilage cap, has been said to preserve hydrodynamic function of the canal (12,13). However, while there have been good vertigo outcomes, hearing outcomes are not widely reported, and resurfacing materials may not achieve a water tight closure and carries a risk of cracking, shifting, or resorbing after closure (12,14).

There is also no consensus on the preferred reconstruction material. Autologous grafting materials (temporalis fascia, bone dust and bone chips), bone wax, and hydroxyapatite cement have all been used. Pliable materials such as bone wax, while durable, when applied too generously risks extension of the wax damaging vestibular structures and causing poorer hearing and vertigo outcomes post-operatively (14,15). Recently, the sandwich technique (fascia, bone meal and fascia) has been described favourably, with studies showing improved hearing outcomes and no vertigo after long term follow up (16,17).

The underwater endoscopic ear surgery (UWEES) technique was first published in 2014 for repair of lateral semicircular fistula technique and this technique may overcome several issues associated with the open microscopic dry approach (18). The microscopic dry approach requires simultaneous delicate removal of the matrix and repair. The matrix is removed with gentle suction on a neuro patty and then quickly placing the repair, minimizing exposure time of the membranous labyrinthine to air. With the underwater technique, the matrix is left intact until the last step, where the mastoid cavity is filled with body temperature isotonic water to mimic perilymphatic fluid. This minimises exposure of the membranous labyrinthine tissues to air and potentially reduces electrolyte changes in the perilymph and endolymph. An endoscope with body temperature irrigation is submerged thus providing a clear operative field without requiring suction which may reduce the risk of direct mechanical damage to the inner ear (19). Another potential advantage of the UWEES technique is that the endoscope provides a wide viewing angle, allowing better visualisation of the middle ear cavity to assist in both the repair and in detection of residual disease. A potential however, exists to worsen the hearing by large volume replacement of endolymph with irrigation solution. There may be also potential seeding of cholesteatoma throughout the ear with irrigation contributing to higher residual disease (20).

The objective of this study is to evaluate the safety and efficacy outcomes of underwater endoscopic repair of labyrinthine fistulae in a case series. This article is presented in accordance with the STROBE reporting checklist (available at https://www.theajo.com/article/view/10.21037/ajo-24-3/rc).

Methods

A retrospective review of a prospectively gathered database of 11 consecutive patients who underwent lateral semicircular canal fistula repair using UWEES from 2015 to 2022 Sydney, New South Wales was performed. These patients were operated on by one of four surgeons (A.S., J.K., N.J., N.P.P.) using the UWEES technique. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013), and approved by Northern Sydney Health Area (2019/ETH12264). Because of the retrospective nature of the research, the requirement for informed consent was waived.

Pre-operative

All patients underwent workup including detailed history taking, clinical ear examination with otoendoscopy, audiogram and high-resolution temporal petrous bone computed tomography (CT) scan. Fistulae were diagnosed clinically and confirmed on pre-operative imaging for all patients. Bone conduction thresholds at frequencies of 500, 1,000, 2,000 and 4,000 Hz were measured. Pre-operative vestibular function testing was possible in 4 patients. The fistula type was assessed based on Dornhoffer and Milewski classification (21).

Surgical technique

All operations were performed under general anaesthetic. Intravenous dexamethasone 8 mg was used intra-operatively for all patients. In 10 cases a canal wall up mastoidectomy (CWU) was performed and in 2 cases a revision canal wall down mastoidectomy (CWD) was performed. Fistula repair was left as the last operative step in all cases (Figures 1,2). Choice of CWU vs. CWD mastoidectomy was determined on a case by case basis based on standard management algorithms including patient factors and disease factors rather than the presence of a fistula. The mastoid cavity was completely filled with body temperature isotonic solution. The matrix was gently removed underwater with continuous irrigation using the 4 mm endoscope (Storz Corp, Tuttlingen, Germany) and Endoscrub (Medtronic corporation, Minneapolis, MN, USA). Irrigation was then stopped and either fascia or composite cartilage floated down to cover the cleared fistula site. The remainder of the sandwich repair, that is applying the bone pate, was performed dry after removal of the irrigation solution. In 4 cases a partial ossicular replacement prosthesis (PORP) was placed during second look procedure following UWEES fistula repair. One revision case had a previous PORP.

Figure 1 Image of labyrinthine fistula.

Figure 2 Image of fistula repair.

Outcome measurements

Patients underwent audiometric examination within the first 5 weeks post-operatively. All patients had continuous follow up with repeat audiogram at a mean of 18 months post-operatively. Five patients had had post-operative imaging at the time of review; five were awaiting repeat imaging. In one case of a revision CWD the decision was made not to re-scan due to low risk of recurrence and no clinical concerns.

The primary outcome of this study is the postoperative bone conduction threshold measured in dB HL from the most recent follow-up. An audiogram tested bone conduction thresholds at frequencies of 0.5, 1, 2, and 4 kHz. A worsening in bone conduction hearing level was described as >10 dB increase post-operatively, stable 0–10 dB change post-operatively and improvement >10 dB decrease post-operatively. Secondary outcomes included subjective vertigo complaint, surgical complications and recidivistic disease. Total follow up duration was measured from date of surgery to date of data analysis.

Data extraction and analysis

Statistical analysis was performed by Wilcoxon signed rank test on SPSS for Windows to analyse pre- and post-operative bone conduction levels. Differences at P<0.05 were considered to be significant.

Results

Demographics

Patient demographics and disease characteristics are depicted in Table 1. Eleven patients (6 male, 5 female) were identified. In 8 patients CWU technique was performed to clear the ear from cholesteatoma and treat the fistula. In 3 patients the labyrinthine fistula was treated during revision surgery (CWU in 1 case and revision CWD in 2 cases). The median age at the time of surgery was 56.4 years (range, 20–80 years). No patients had an intact labyrinthine endosteum. Ten out of the eleven patients had a type II fistula (5 type IIa, 5 type IIb) and one type III. In every case, temporalis fascia was used to repair the fistula. In 5 patients a ’sandwich’ composed of temporalis fascia, bone pate and fascia were used, in 4 cases temporalis fascia and composite cartilage, and in 2 cases a combination of temporalis fascia, composite cartilage which was covered with bone pate after drainage. Intra-operatively, 9 patients were found to have intercurrent ossicular erosion. All 9 had incus and malleus erosion, and 2 also had stapes erosion. Five patients had fallopian canal erosion, and two patients had tegmen dehiscence. Six patients had post-operative imaging (at a mean of 21 months post-operatively). Three patients had a second look procedure in place of post-operative imaging, one patient had clinical observation only due to the previous CWD mastoidectomy, and one patient was lost to follow up.

Primary outcome: comparison of pre- and postoperative hearing examination (Table 2)

A Wilcoxon signed-rank test showed that there was no significant decline of hearing after UWEES (Z=−0.664, P=0.51). We found a mean pre-operative bone conduction threshold (0.5–4 kHz) of 23.3 dB [standard deviation (SD) 15.5]. After a mean of 18 months follow-up (SD 16) this increased to 25.1 dB post-operatively (SD 16.6).

Subgroup analysis of hearing improvement showed no differences between Dornhoffer type 2a and 2b ossicular reconstruction (Δ −0.5 and Δ −2.7, P=0.90 and P=0.93 respectively). The Dornhoffer type 3 ossicular reconstruction gave the poorest hearing outcomes (Table 3).

Secondary outcome: vertigo, recidivism, other complications

Of the 11 patients, 9 patients had vertigo pre-operatively (Table 4). Of these 9 patients, 2 patients had vertigo post-operatively which resolved within 6 months. One patient had persistent vertigo beyond 6 months on tragal pressure only. The two patients who did not have vertigo pre-operatively also did not have vertigo after UWEES.

Patients had a mean total follow up of 34 months (SD 22). After UWEES, 1 patient had recurrent disease located in the attic, aditus and antrum. One patient had residual disease in the epitympanum. Both cases were diagnosed on clinical examination and confirmed on post-operative imaging and during revision surgery. During revision surgery both repairs were found to be intact. The recurrent cholesteatoma was removed successfully without damaging the repair. Of the remaining patients, one had an equivocal scan and was awaiting repeat imaging. One patient was assumed to have recurrent disease on clinical examination and imaging however no cholesteatoma recurrence was found on second look surgery. One patient was lost to follow up. There were no patients with pre-operative or post-operative facial nerve weakness. One patient had an intra-operative cerebro-spinal fluid (CSF) leak noted after dissection of cholesteatoma in a region of tegmen erosion which was repaired successfully with no further leak noted. No other complications were identified.

Discussion

UWEES is a relatively new technique used to treat labyrinthine fistulas secondary to cholesteatomas, with potential advantages including a wider surgical viewing angle to allow better visualisation of the middle ear cavity. The mastoid cavity is flooded with body temperature isotonic water which mimics perilymphatic fluid, potentially reducing electrolyte changes in the perilymph and endolymph, as well as damage to the membranous labyrinthine from exposure to air and direct mechanical suctioning. Underwater dissection of tissue also aids in separation of the disease from normal tissue. In this case series, there was no significant difference in hearing after UWEES, which is comparable to previous studies (17,20,22-24). The microscopic technique has also shown no significant hearing difference post-operatively, with majority of studies reporting stable or improved hearing outcome (1,25-27). Theoretically with the UWEES method the membranous labyrinthine is less likely to be exposed to both air and suction during removal of the matrix. Furthermore, there is likely more room for improvement with UWEES, as surgeons become more versed with the technique (28,29). Currently, more rigorous comparative research is required to determine which technique is superior.

The patients in this study were all Dornhoffer 2a or 2b aside from one type 3 patient, with no significant difference in type 2a and 2b fistula hearing outcome post-operatively. Meng et al. compared microscopic and UWEES technique in two separate groups (group 1 underwent microscopic repair and group 2 underwent UWEES repair) and found that there was a significant difference in air-bone gap between the two groups for type IIa and IIb fistulas post-operatively, but not for type I (17). However, group 1 fistulas were repaired with a simple fascia covering, while group 2 fistulas were plugged with fascia and bone meal then covered with bone wax. It is likely that the poorer hearing outcome is secondary to destruction of the membranous labyrinthine intra-operatively from canal plugging rather than the UWEES technique itself. However, there are currently no other papers comparing UWEES and microscopic technique in a single study, and further research is required. In the same study, one patient with type 3 fistula had a significant decline in hearing post-operatively. However, since analysing the data, further follow up showed that this patient’s bone conduction thresholds returned to near pre-operative levels (i.e., <10 dB change from pre-operative). Patients with type 3 fistulas have been shown in the literature to have severe sensorineural deafness post-operatively regardless of the operative technique (17,30). Longer follow up may show further recovery of hearing outcomes.

There was no significant vertigo post UWEES. Of the 11 patients, only 1 patient had ongoing vertigo after 6 months when examined with tragal pressure. UWEES appears to have good preservation of vestibular function post-operatively, with studies showing only a small proportion of patients experience vertigo post-operatively, and resolve with no long-term vertigo (17,20,23,24). Previous studies generally show a greater improvement in post-operative vertigo using the microscopic approach; however, this may be largely due to the repair technique. These studies often use either a simple fascia covering or a sandwich covering which is less likely to disturb the delicate vestibular structures compared to canal plugging (16,17,31,32). In this study, five repairs were completed with the sandwich technique with the remaining using a fascia and cartilage covering which could have contributed to better vertigo outcomes.

There was one patient with recurrent disease post UWEES (9%). This is a similar rate to both recent UWEES studies and traditional microscopic methods which report a recurrence rate of between 10–40% (22,33-35). One patient in this study had residual disease (9%). Previous microscopic studies have reported residual rates of 20–30% (36-38). Most patients in this study underwent CWU mastoidectomy, which has been shown to have better protection of the exposed labyrinthine and potentially better hearing outcomes, but poorer control of recidivistic disease (39-43). Assumptions have been made that CWD is associated with lower rate of recurrent/residual disease due to the extensive visualisation with removal of the posterior canal wall (35,44). While it is important to consider the risk of recidivistic disease, there is a consensus that the choice of surgical technique should be based preferentially on pre-operative hearing, comorbidities and extent of cholesteatoma (1,3,5,16,30). Combining UWEES technique with CWU may reduce the rates of recidivism with the wider viewing angle and clearer operative field which the UWEES approach provides, with the downside that it would increase the difficulty of revision surgery and have a higher risk of interrupting the fistula repair (45,46). However, longer follow up period and a larger sample size are required to draw reasonable conclusions of recidivism.

Limitations

The results from this work suffer from differences in surgical technique and material which may have influenced the overall outcomes for each patient, based on surgical preference of the four different surgeons. The sandwich technique (fascia, bone, fascia) which was used on 5 patients in this study has been reported to reduce symptoms of vertigo due to capping of the fistula intra-operatively (16). With a larger pool of patients or a meta-analysis, it will be possible to assess these variables for confounding bias.

Vestibular function tests were not performed for the patients pre- and post-operatively, as it is a difficult and time-consuming test which would not necessarily change management. Patients may have had pre-operative vestibular damage with compensation prior to surgery. This is less likely in this study as majority of the patients (82%) had subjective vertigo pre-operatively. However, caloric testing or cervical vestibular evoked myogenic potential will more objectively assess vestibular outcomes, and can be considered for future studies.

Residual disease may be under reported due to inconsistent post-operative imaging by the time of review. Patients were followed up with routine clinical examination, and if recidivistic disease was suspected, they would proceed to CT imaging. Several patients proceeded straight to relook surgery without repeat imaging, however in these patients no recurrent or residual disease was found. Non-echo-planar diffusion weighed magnetic resonance imaging (non-EPI DW MRI) was inconsistently performed due to short follow up times in some patients.

The shortest length of follow up was 13 months for one patient. Short follow up durations were either due to patient compliance, or recent surgery at the time of review.

Conclusions

UWEES may be a safe and effective method of treating labyrinthine fistulas secondary to middle ear cholesteatoma. There were no significant secondary complications found in these patients. Further research is required to assess long term outcomes and compare UWEES with the traditional microscopic approach in controlled or randomized cohorts.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://www.theajo.com/article/view/10.21037/10.21037/ajo-24-3/rc

Data Sharing Statement: Available at https://www.theajo.com/article/view/10.21037/ajo-24-3/dss

Peer Review File: Available at https://www.theajo.com/article/view/10.21037/ajo-24-3/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://www.theajo.com/article/view/10.21037/ajo-24-3/coif). A.S. serves as an unpaid editorial board member of Australian Journal of Otolaryngology from January 2019 to December 2024. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013), and approved by Northern Sydney Health Area (2019/ETH12264). Because of the retrospective nature of the research, the requirement for informed consent was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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