The endoscope has transformed the way we observe, understand, and treat chronic ear disease. Improved view, exclusive transcanal techniques, assessment of ventilation routes and mastoid tissue preservation have led to decreased morbidity and functional enhancement of minimally invasive reconstruction of the middle ear. The philosophical identity of endoscopic ear surgery is evolving; new research, long-term results, and widespread acknowledgement of its postulates will undoubtedly define its role in otology.
Key points
- •
The endoscope allows improved view and reconstruction of tympanic membrane perforations.
- •
Endoscopic myringoplasty is feasible by a transcanal approach regardless of perforation size or anatomy of the ear canal.
- •
The endoscopic approach for tympanoplasty has not surpassed microscopic anatomic or functional outcomes, but it is undeniably less invasive and better tolerated by patients.
- •
Assessing the ventilation routes and preserving mastoid tissues may enhance functional outcomes for minimally invasive reconstruction of the middle ear.
Video content accompanies this article at http://www.oto.theclinics.com .
Introduction
Tympanic membrane (TM) perforations are a common problem, most often as consequence of middle ear infection, traumatic rupture, or postoperative complication. Despite the autoregenerative capacity of the eardrum, chronic perforations may be subject to surgical repair. The main goal of tympanoplasty (TP) is to restore anatomy and function and to eliminate disease; therefore, an uninterrupted TM, an air-containing mucosal-lined middle ear and a secure connection between the TM and the inner ear fluids are essential.
The introduction of endoscopy to otologic surgery was underpinned by the ability to provide better access and view to otherwise hidden areas of the middle ear, such as the retrotympanum, anterior epitympanum, or middle ear folds, resulting in better appreciation of their relationships. This improved visualization results from closeness of the light source to the surgical field and wide angle optics, thereby transforming the external auditory canal into an excellent surgical portal.
The endoscopic revolution has also lead to advances in anatomic and pathophysiologic concepts, which elucidate the role that middle ear folds play in blocking middle ear ventilation routes in patients with chronic otitis media. A more conservative approach preserving the mastoid tissues decreases morbidity and may improve postoperative middle ear ventilation, owing to their role in middle ear gas exchange. Systematic intraoperative visualization, analysis, and in some cases removal of these folds should be regarded as essential to restore middle ear physiology. Endoscopes better illustrate these findings and aid in engaging this new philosophical perspective.
Endoscopic procedures, nevertheless, have several disadvantages. Given the diameter of the endoscope in relation to the ear canal, dissection may only be feasible with 1 hand and, thus, inefficient and challenging, chiefly when there is blood in the surgical field. Refinement of endoscopic skills and adopting precautionary hemostatic measures are paramount, a task more difficult to master by the surgeon with limited endoscopic training. Other caveats relate to heat dissipation and ototoxicity of antifog solutions. Concern over thermal injury is warranted for elevated temperatures may occur up to 8 mm from the endoscope tip ; thus, smaller 3-mm endoscopes with submaximal light intensity (<60%), frequent removing–repositioning, irrigation of the surgical field, and suction are recommended.
Unlike the microscope that contemplates the surgical field from the outside, the endoscope itself is not immune to damage if unintentionally struck by a bone curette or a burr. Most instruments in use today were not customized for an endoscopic approach (EA), but rather migrated from traditional microscopic techniques; consequently, there will be a great demand for better and more refined tools in years to come.
Despite these potential drawbacks, the future of endoscopic ear surgery (EES) for minimally invasive functional reconstruction through a transcanal approach is enticing.
Introduction
Tympanic membrane (TM) perforations are a common problem, most often as consequence of middle ear infection, traumatic rupture, or postoperative complication. Despite the autoregenerative capacity of the eardrum, chronic perforations may be subject to surgical repair. The main goal of tympanoplasty (TP) is to restore anatomy and function and to eliminate disease; therefore, an uninterrupted TM, an air-containing mucosal-lined middle ear and a secure connection between the TM and the inner ear fluids are essential.
The introduction of endoscopy to otologic surgery was underpinned by the ability to provide better access and view to otherwise hidden areas of the middle ear, such as the retrotympanum, anterior epitympanum, or middle ear folds, resulting in better appreciation of their relationships. This improved visualization results from closeness of the light source to the surgical field and wide angle optics, thereby transforming the external auditory canal into an excellent surgical portal.
The endoscopic revolution has also lead to advances in anatomic and pathophysiologic concepts, which elucidate the role that middle ear folds play in blocking middle ear ventilation routes in patients with chronic otitis media. A more conservative approach preserving the mastoid tissues decreases morbidity and may improve postoperative middle ear ventilation, owing to their role in middle ear gas exchange. Systematic intraoperative visualization, analysis, and in some cases removal of these folds should be regarded as essential to restore middle ear physiology. Endoscopes better illustrate these findings and aid in engaging this new philosophical perspective.
Endoscopic procedures, nevertheless, have several disadvantages. Given the diameter of the endoscope in relation to the ear canal, dissection may only be feasible with 1 hand and, thus, inefficient and challenging, chiefly when there is blood in the surgical field. Refinement of endoscopic skills and adopting precautionary hemostatic measures are paramount, a task more difficult to master by the surgeon with limited endoscopic training. Other caveats relate to heat dissipation and ototoxicity of antifog solutions. Concern over thermal injury is warranted for elevated temperatures may occur up to 8 mm from the endoscope tip ; thus, smaller 3-mm endoscopes with submaximal light intensity (<60%), frequent removing–repositioning, irrigation of the surgical field, and suction are recommended.
Unlike the microscope that contemplates the surgical field from the outside, the endoscope itself is not immune to damage if unintentionally struck by a bone curette or a burr. Most instruments in use today were not customized for an endoscopic approach (EA), but rather migrated from traditional microscopic techniques; consequently, there will be a great demand for better and more refined tools in years to come.
Despite these potential drawbacks, the future of endoscopic ear surgery (EES) for minimally invasive functional reconstruction through a transcanal approach is enticing.
Has the endoscope outperformed the microscope?
In the narrow anatomy of the ear canal, surgery may be technically very demanding. To grant proper exposure, permeatal endaural incisions or postauricular approaches were used mainly for anterior and subtotal perforations and pediatric cases. Without exception, all publications in the field agree that regardless of ear canal anatomy or age, TP can be performed endoscopically through a transcanal approach. Increased postoperative pain, a numb or protruding pinna, and retroauricular scar or depression are frequently associated with more morbid approaches; therefore, a transcanal approach is preferred by patients because it grants improved comfort and aesthetics. As a result, endoscopic techniques for TP differ in 3 main aspects: (1) grafting material, (2) position of the graft in relation to the fibrous annulus and tympanic remnants, and (3) treatment of middle ear folds and ventilation routes.
Comparison of reported surgical outcomes between the endoscope and microscope may be explained not only by technique variants or differences in patients underlying pathology, age, or risk factors, but by the sole definition of success. Normal middle ear function after TP clearly requires more than an intact graft. An imperforate lateralized graft in the middle of the ear canal or a “Kevlar-armored” cartilage graft with poor audiological outcomes are equally undesirable. Therefore, a stricter definition of success, including anatomic and functional criteria as well as prevention of complications, has been promoted, even when confronted with more modest results ( Box 1 ). Complications have yet to be reported on endoscopic TP; EES is very anatomic and, as such, should bestow little trauma to the middle ear. The overzealous surgeon may misuse this tremendous advantage by inordinate manipulation around the ossicular chain when treating the middle ear folds and ventilation routes. Rarely, taste disturbance may result from traction or section of the chorda tympani.
- 1.
Anatomic success
- a.
Intact graft without perforation or lateralization.
- a.
- 2.
Functional success
- a.
Improvement in hearing by assessing the ABG of less than 20 dB (0.5–3 kHz) or conservation of hearing (if normal preoperative audiometry).
- b.
Aerated middle ear space (TM in normal anatomic position).
- a.
- 3.
Prevent complications
- a.
Ossicular disruption or acoustic trauma.
- b.
Taste disturbance (chorda tympani injury).
- c.
Neurovascular injury.
- a.
Abbreviations: ABG, air–bone gap; TM, tympanic membrane.
Given the logical learning curve for EET, one would expect lengthier surgical times and hospital stays, but no significant change has been reported; better yet, it may be even faster. This suggests a steeper learning curve for otologic surgeons acquainted with endoscopic sinus surgery.
Several notable studies have directly compared anatomic and functional success for in TP by an EA or microscopic approach (MA). Very similar graft survival (MA 83%–86% vs EA 83.3%–90%) and functional success rates (MA 85%–90% vs EA 90%) have been reported in adults, using an underlay technique (fascia or perichondrium).
Dundar and colleagues compared 32 EA with 29 MA for type I TP in children using a cartilage–perichondrial graft by the underlay technique, with compatible graft success (MA 93.1% vs EA 87.5%) and air–bone gap gain (MA 13 dB vs EA 12.2 dB). Cohen and colleagues compared outcomes after 13 EA versus 19 MA type 1 myringoplasties in a pediatric cohort. No differences in graft closure (MA 84.6% vs 78.9% EA; P >.99), mean PTA threshold improvement (MA 27.8 dB vs EA 21.33 dB) or surgical time where shown. In a retrospective study, Nader and colleagues compared 23 MA versus 22 EA, using an underlay technique in children (5–16 years old), with anatomic success at the 1-year follow-up of 82.6% for MA versus 90.9% for EA ( P >.05). No difference in preoperative or postoperative air–bone gap values, bone threshold impairment, or postoperative complications was observed between the groups.
TP in children is often regarded as being less successful because of their higher propensity to infection, impaired Eustachian tube function, and adenoidal tissue hypertrophy. In the endoscopic era, previous adenotonsillectomy, active infection, auditory tube dysfunction, perforation size, and age have not been reported as negative prognostic factors for pediatric TP.
Surgical treatment of middle ear folds for clearing middle ear ventilation routes up to the mastoid cell system is the backbone of EES philosophy. Postoperative improvements in gas exchange and overall middle ear physiology converges on this premise. The anatomy of the epitympanic diaphragm, spectrum of pathologic variants, and their dynamic sequelae are somewhat perplexing. Marchionni and colleagues have shed light on the subject describing 3 different types of TP in patients with selective epitympanic dysventilation syndromes with encouraging results. Several questions have yet to be answered: (1) Can surgery warrant isthmus permeability in the long term? (2) Inlay, interlay, and overlay techniques cannot properly address this problem; how does that affect outcomes and patient selection? (3) Underlay grafting may decrease not only middle ear space but narrow the anterior isthmus (as frequently observed in revision cases), does this justify over–under grafting as instead?
Endoscopic tympanoplasty and grafting selection
The TM repairs mainly by epithelial migration, grafting materials act as scaffolds to guide the cell migration from the edges of the perforation, facilitating closure by providing a patch on which the neomembrane grows. Because TM must heal by secondary intention, the size and location of the perforation may influence the results.
Anatomic and physiologic factors might contribute toward a less favorable prognosis for graft survival in anterior quadrant and marginal perforations as a result of vascular supply, metabolic activity, and inadequate graft support. Fluorescein angiography has shown a more vigorous vascular supply for the posterior TM and a greater metabolic demand at the anterior annulus could explain the greater risk for necrosis and delayed healing. Specific technical difficulties in repairing anterior perforations as a bulging canal wall or the lack of a structure to support the graft anteriorly may also lead to poorer outcomes. Complete visualization of the TMP and surrounding annular rim, as well as correct graft placement are requirements well-suited for the EA. Most of the time, transcanal endoscopy avoids canalplasty, even for anterior or total perforations.
Recently, there have been reports of an 87.5% to 95.5% TM closure and 91% functional success (6.4–8.5 dB air–bone gap gain) for anterior perforations grafted with cartilage by an expeditious totally endoscopic transcanal inlay butterfly or ( Fig. 1 ) pushthrough technique.
Temporalis Muscle Fascia
Temporalis muscle fascia (TMF) remains the gold standard in the clinical practice and the main reference against which other grafting materials are compared. The TMF microstructure is pliable and abundant; however, its shrinkage can be unpredictable because the gaps between its elastic fibers are filled with connective tissue that shrinks and thickens more than elastic fibers do. Graft success rates of EA range between 82% and 93% and are consonant with the 80% of 10-year follow-ups of both underlay and overlay microscopic techniques. A soft TMF is difficult to unfold and arrange inside the ear canal; a useful surgical pearl is to fix the graft’s edge against the ear canal with the endoscope tip while unfolding with the other hand.
Cartilage and Perichondrium
As opposed to other grafts, cartilage provides a more robust scaffold, and is well-tolerated by the middle ear because it induces little tissue inflammation, resists infection during the recovery process, and can be viable even after delayed epithelization owing to its bradytrophic properties and nourishment by diffusion. It first became the preferred grafting material for advanced middle ear pathologies when an increased risk of Eustachian tube dysfunction was expected, paving the way for its widespread use in large perforation and primary low-risk cases; hearing results have shown to be comparable to tragal perichondrium and TMF. Dornhoffer’s 1000 TP series using cartilage grafts proved to have a very low recurrence rate of 4.2%, even though 47% were revision cases. Whenever risk factors for graft failure are identified (subtotal or anterior perforations, significant inflammatory changes in middle ear mucosa or contralateral ear pathology ), an alternative durable graft material such as cartilage must be considered.
Cartilage is also versatile, because it can be used with or without perichondrium as a shield, island (single or bipedicled), palisade, or plug. For endoscopic purposes, it is much easier to allocate with 1 hand and can also be easily harvested from the tragus. High graft take rates have been published for EA in both adults (87.5%–96%) and children (88%–100%).
The characteristics of cartilage are worse than more pliable tissues because of its thickness, rigidity, and potential restriction of middle ear space. Experiments using variable cartilage thickness have shown that split thickness grafts of 0.5 mm or less have acceptable acoustic transfer with good mechanical stability. In the clinical setting, however, there has been some controversy as to whether slicing the cartilage graft is necessary to attain optimal hearing results. Another limitation of cartilage grafting is losing the apparent translucency of the membrane; therefore, otoscopy is unreliable for postoperative documentation of recurrent cholesteatoma or middle ear effusion.
Fat
Autologous fat has received attention as a safe and effective material for inlay grafting in small TMP with success rates between 76% and 92%, similar to those of TMF and paper patch. Additionally, fat grafts secrete angiogenic growth factors that promote neovascularization and tissue repair, thus increasing the scanty blood supply around the TMP. Earlobe and subcutaneous retroauricular fat are quickly obtained with low morbidity, but fat supply is poor, and so generous sources like abdominal fat have been promoted. In medium or large pars tensa perforations of more than 30%, most authors agree that success rates decrease with fat grafting. There are no reports in the literature on outcomes after endoscopic inlay fat myringoplasty.
Despite the large variety of scaffolds and surgical techniques available there is still no consensus on the optimal alternative for the TM repair. Thus, new therapeutic approaches are needed to overcome these drawbacks.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
