Introduction: Totally endoscopic ear surgery (TEES) is gaining in popularity globally and has revolutionized access to difficult areas in the middle ear cleft. It is, however, not without its own challenges and pitfalls and in some units is slow to be introduced into routine practice.

Methods: A prospective review and cohort study of all otological procedures performed by the senior author was undertaken and grouped according to technique from June 2013 to December 2020. Particular focus is given to our TEES procedures and we present our patient selection process, complication rates, and recurrence rates and follow up protocol. A non-systematic narrative literature review was undertaken.

Results: Just under one third of cholesteatoma cases were deemed appropriate for the TEES approach. At one year follow up, there was an 11.1% rate of recidivism. The complication rate was 0%.

Conclusion: The use of the endoscope is an invaluable tool in both middle ear surgery and training of junior doctors. It may also have economic benefits. Rigorous training and following a stepwise approach from simple procedures to more difficult is essential to overcome the learning curve associated with this technique.

Access to the middle ear is notoriously challenging. It was revolutionized by Wullstein with the introduction of the microscope, and he is considered by many to be the founder of modern ear surgery. Further mitigation of the issue with access has been described with the use of endoscopes and this technique has been increasing in popularity over the last few decades. It offers enhanced panoramic views of the middle ear cleft and improved access to previously challenging areas such as the supratubal recess, sinus tympani and key ventilation routes including the isthmus tympani anticus and the epitympanic diaphragm. Jean-Marc Thomassin gave a detailed account of the history of endoscopic ear surgery (EES), from the development of the Hopkins Rod in 1967, to the use of a flexible fiber optic scope on cadaveric models and animals in 1983 by Mer, to modern techniques and the advent of an International Working Group on Endoscopic Ear Surgery in 2009 ?1?. Historically, the endoscope was employed as an adjunct in second look or revision surgery [2]; however it has now emerged as a valuable tool in primary modality surgery. A validated classification system for the extent of endoscopic dissection has been proposed by Cohen ?3? et al in 2017 [Table 1].

Table 1: Cohen Classification of Endoscopic Ear Procedures (2017).

Since then, a newer (2020) classification system has been proposed but is yet to be widely accepted and is summarized below [4]. Type 1: attic retraction pocket requiring either ventilation tube insertion or resection with cartilage reconstruction. Type 2: Cholesteatoma limited to the attic or endoscopy can confirm complete removal Type 2a: Requires curette Type 2b: Requires electric drill or chisel Type 3: Cholesteatoma not limited to the attic where a combination of endoscopic and microscopic techniques are required to confirm complete removal Type 4: Extensive lesions requiring microscopic removal only Using these classification systems and estimating the extent of the lesions both clinically and radio logically is key for an endoscopic approach to middle ear cholesteatoma. EES can be defined by 3 principles [5]. The first is the use of the ear canal as a natural conduit to the tympanic cavity, obviating the need for a post auricular scar and its potential associated morbidity. The second is as for any other middle ear surgery; to remove disease, restore normal middle ear mucosa and mastoid ventilation routes. The third is particularly relevant to purely endoscopic techniques: to preserve as much normal anatomy as possible by minimizing dissection of normal bone and soft tissue that is usually required simply for exposure. Recent studies have focused on the replacement of the microscope with the endoscope; however this concept has still not been widely adopted, and substantial heterogeneity and publication bias is thought to limit the integrity of the existing evidence base [6].

The aim of this study is to present a case series of our primary modality endoscopic ear surgeries. Our techniques, patient selection, complications, recurrence rates in cholesteatoma and any other pitfalls we have been faced with whilst setting up this service in our institution will be noted. We seek to contribute to the ever expanding body of evidence to support this practice and to highlight its benefits.

A prospective review and cohort study of all otological procedures performed by the senior author was undertaken and grouped according to technique from June 2013 to December 2020. Particular focus is given to our TEES procedures and we present our complication rates, recurrence rates and follow up protocol. A non-systematic narrative literature review was undertaken.

Technique In our institution it is routine to perform a high resolution CT Temporal Bones for any patient with clinical cholesteatoma, to provide an anatomical road map and to assist with patient selection, counseling and consent. Among the indications for purely endoscopic procedure are:

Disease Factors: Disease limited to the epitympanum or mesotympanum with minimal disease in the mastoid Absence of preoperative concerns of perilymph fistula, high riding jugular bulb or aberrant carotid artery.

Patient Factors:

Patient preference following informed consent

Absence of bleeding diathesis

Pre-operatively the senior surgeon will obtain written informed consent not only for the endoscopic surgery but also for the possibility of conversion to an open procedure, along with a post auricular scar. The other complications that are mentioned are bleeding, pain, infection, chorda tympani injury, facial nerve injury, reduced hearing, dead ear, vertigo, tinnitus and recurrence with the possibility of further surgery in the future.

Rigid 4mm endoscopes with angulation ranging from 0 to 70° are used as the primary visualization tool. Endoscopic ear surgery is single handed surgery, with scope introduction using one hand and instrument manipulation with the other. No ear metal speculum is required. Specific middle ear instruments have been developed, inclusive of those with suction attached, to facilitate dissection in confined spaces. Our experience has been satisfactory with utilization of conventional open middle ear/mastoid dissection sets, with malleable suction tips contoured according to disease extent.

Facial nerve monitoring is used for all mastoid and middle ear cholesteatoma procedures, but is deemed not relevant to tympanoplasty procedures. The operating microscope is prepped and draped in advance of all endoscopic cases, allowing for rapid conversion to open access should the need arise.

A careful endoscopic examination of the tympanic membrane is carried out prior to commencement of any endoscopic mastoid operation, to delineate distribution of the disease process and to establish the extent of any proposed dissection. Local anaesthetic with 1:10000 lidocaine infiltrations to the lateral portion of the external auditory canal assists in both haemostasis and hydro dissection of tissue. A tympanomeatal flap is elevated approximately 5mm from the tympanic annulus in the osseous portion of the canal. Small neurosurgical patties assist in the elevation of soft tissue flaps, with one placed above the flap and one beneath, to assist in soaking up a potential bloody field of dissection. As far as possible, the endoscope is kept lateral to the annulus in the early stages of surgery to avoid injury to the middle ear structures. In keeping with the major principles of EES, healthy bone should be preserved unless curettage or bone burring is required for access.

A small incision is made over tragal cartilage skin to harvest cartilage with mucoperichondrial graft. Cholesteatoma and granulation tissue is dissected and removed, and the relevant anatomy can be successfully delineated and preserved. Ossiculoplasty and grafting of the tympanic membrane is technically difficult due the one-handed nature of endoscopic ear surgery; however, visualisation of exact graft and prosthesis placement is magnified and enhanced. These points are illustrated in the figures below, showing the enhanced view of the middle ear cleft after elevation of a tympanomeatal flap without drilling of the mastoid air cell system [Figure 1].

Figure 1: A) Intraoperative view of left TEES procedure following elevation of tympanomeatal flap. Arrow head: anterior ligament of malleus, arrow: encapsulated cholesteatoma and B) As before. Arrow head: anterior ligament of malleus, arrow: following dissection and removal of cholesteatoma sac

1. Cholesteatoma Surgery

Table 2: Summary of cholesteatoma procedures grouped by approach.

Just under one third of all cholesteatoma cases in our institution were deemed appropriate for primary modality endoscopic surgery. 18 of 23 TEES patients had 1year of follow up. At this juncture, cholesteatoma recurrence/ recidivism were noted in 2 patients in whom surgery was carried out purely with the endoscope (11.1%). Follow-up for cholesteatoma recurrence in our institution is a via Diffusion Weighted MRI (non-ECHO planar) at 1 year post surgery in an asymptomatic patient. In postoperative patients with symptoms, primarily otorrhea and aural fullness, an endoscopic “second look” procedure is carried out. Revision surgery, if required, is undertaken via the standard post auricular approach with the microscope [Table 3].

2. Core Otology

Table 3: Summary of core otology procedures grouped by approach.

Non-cholesteatoma surgery has seen a significant shift toward endoscopic approaches in our unit, with tympanpolasties, myringoplasties, and exploratory tympanotomies considered the prime procedures suitable for such a technique. The size and position of tympanic membrane perforations are key to successful outcomes endoscopically. Perforations smaller than a quadrant of the membrane are much easier to address, although larger perforations have been successfully corrected with such a technique. Posteriorly-based perforations are ideally suited for endoscopic repair, and access to anterior perforations with anterior canal overhangs are again easier to access with the endoscope. Large subtotal perforations are repaired via an open microscopic technique [Table 4].

3. Ventilation

Table 4: Summary of ventilation tube related procedures grouped by approach.

There has been a switch to endoscopic surgery with regards to ventilation tubes, such that they are performed almost exclusively now. This is an invaluable teaching tool for surgeons in training, and the viewpoint to both the trainee and trainer is shown below: [Figure 2].

Figure 2: Intraoperative view of grommet insertion as used as a training case.

Endoscopic ear surgery, or "EES," is defined as the use of the rigid endoscope, in contrast to microscopic techniques, to visualize and gain access to the middle ear cleft. It is not a new technique, having first been described in 1977 by Ohnsorge at the Würzburg ENT clinic [7]. Regarding TEES, the obvious benefit of improved access is supported in the literature, in particularly in stapes surgery. The hearing outcomes in stapedotomy are comparable to standard techniques without the need for canalplasty, endaural incision and curettage, with less mobility of the chorda tympani [8]. TEES has also been shown to be cost effective in the management of cholesteatoma, despite the initial investment in new equipment and training, having a mean direct cost reduction of AUD$2978.89 (approximately €1,931) per operation, when compared to canal wall up mastoidectomy [9]. The parallel use of LASER in TEES is gaining in popularity an exciting new development in middle ear surgery. Not only this, a recent systematic review has shown additional benefits such as offsetting some disadvantages of single handed surgery with bloodless and non-contact LASER ablation of tissue [10]. However, despite the benefits it proffers, the endoscope has been accepted mostly as an adjunct to the microscope with the wider acceptance of totally endoscopic ear surgery or “TEES” being much slower.

One of the earliest concerns was that heat transference from the tip of the endoscope could ostensibly cause tissue damage. Studies have shown that the temperature at the tip of the endoscope is markedly attenuated to what was initially estimated. This has been obviated with regular removal of the endoscope from the ear canal and application of antilog at regular intervals [11]. The other major drawbacks of the technique include the single handed nature of the surgery and the perceived lack of depth perception. A number of ways of overcoming these issues have been proposed. With regards to the learning curve, commencement with simple cases such as micro suction of cerumen and working in a stepwise approach towards more complex cases has been shown to be effective both in the literature [12-15] and in our own experience.

Published data regarding the learning curve of EES is lacking, and some authors have suggested that the number of procedures required for competency may follow other set procedures [14,15] such as congenital aural atresia surgery [16] translabyrinthine removal of vestibular schwannoma [17] and stapedotomy [18] requiring between50-60 procedures before competency is thought to have been achieved.

Pothier [14] in his seminal paper also suggested that collaborating with a surgeon with previous experience can lessen the learning curve for EES and can provide insight into many of the surgical “pearls” that may be passed on from familiarity with the technique.

The second major perceived disadvantage is the lack of depth perception and the loss of binocular vision afforded by the microscope. However, this is a similar issue as encountered with endoscopic sinus surgery which is now the gold standard in rhinology. Small continuous movements of the endoscope to judge the depth of the field and using surgical tools such as a round knife to measure distances will overcome the optical distortion or ‘fish-eye’ effect until the surgeon becomes accustomed to the technique [11].

The following tables exhibit a sample of the available literature regarding the two techniques (endoscopic and microscopic) and recidivism rates [Table 5].

Table 5: Summary of recidivism rates in open/microscopic cholesteatoma procedures from recent studies.

Table 6: Summary of recidivism rates in endoscopic/combined endoscopic and microscopic cholesteatoma procedures from recent studies.

Our complication rate is 0%, but our recurrence/residual rate of 11.1% is higher than some reports. This practice is still in its infancy in our unit and although the recidivism rate is still at an acceptable level it should continue to improve with iterative audit cycles and improving on technique. We propose that EES is a safe and effective procedure provided the surgeon has received adequate training. There are myriad courses available internationally.

EES has proven to be a vital training tool in our institution with the operating surgeon and observers sharing the same image on screen. It allows for real time demonstration of anatomy and procedural steps for both surgeons in training and undergraduates. It now forms a large part of the national temporal bone training day held for specialist registrars in Royal College of Surgeons in Ireland annually.

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Corresponding Author: Emma Keane, Department of ENT, St Vincent’s University Hospital, Ireland. E-mail: emmakeane@rcsi.ie.

Copyright: ©2022 All copyrights are reserved by Keane E, published by Coalesce Research Group. This work is licensed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.