Endoscope-Assisted Tympanomastoidectomy for Cholesteatoma

Improved Visualization

Revision tympanomastoidectomy with recurrence or residual disease in the tympanic cavity is thought to be a result of suboptimal initial access and exposure. ^, Therefore, the primary advantage of transcanal endoscopic ear surgery (TEES) or endoscope-assisted ear surgery (EAES) over conventional microscopy is the wide field of view offered by straight and angled scopes in the visualization of hard-to-reach sites. The straight-line view offered by microscopy offers only a glimpse of sites notorious for residual cholesteatoma, namely the sinus tympani, epitympanum, hypotympanum, supratubal recess, and intercrural space. ^, Using computerized models of computed tomography (CT) scans, Bennett et al. found that a 0-degree endoscope outperformed the microscope for every subsite of the tympanic cavity, and that visualization only increased with 30- and 45-degree scopes. With rates of residual cholesteatoma ranging from 10% to 43% after canal wall-up (CWU) tympanomastoidectomy, clearing the aforementioned sites of disease is paramount.

Minimizing Residual Disease

The ability of TEES and EAES to visualize difficult-to-reach areas has led to a decline in rates of residual disease in several reports. Thomassin et al. reported a decrease in rates of residual disease from 47% to 6% after introducing otoendoscopy. Similarly, Ayache reported identifying residual disease in 44% of epitympanic and 75% of retrotympanic cases in which endoscopy was used after microscopic excision of disease. In using otoendoscopy, the group was able to reduce their postauricular tympanoplasty rate significantly from 22% to 3%. While several other reports include low rates of residual disease after TEES/EAES, Yawn et al. reported a rate of 13% compared to a 7% residual rate in their patients undergoing microscopy. In an analysis of 235 pediatric patients undergoing TEES or EAES, the authors found significantly less residual disease in the middle ear, but not in the other subsites. There was no difference in the rate of residual disease, however, when analyzing only those who underwent second-look procedures. The authors observed fewer second stage surgeries in the endoscopic group due to increased confidence in the initial resection and calculated a number needed to treat of nine for endoscopic surgery preventing residual disease. When residual or recurrent disease is present after TEES/EAES, it is often in the form of smaller, more easily resectable pearls. ^, Regardless of the technique used, attention must be paid to field clarity in the way of bleeding, as this is a significant predictor of leaving residual disease at the time of dissection.

TEES/EAES ARE Minimally Invasive

Proponents of TEES and EAES tout its minimally invasive nature as a major advantage over conventional microscopy. Otoendoscopy with intervention can even be performed in children with smaller ear canals; generally, as long as a 4.5-mm speculum can fit in the canal, endoscopy is feasible. Avoiding mastoidectomy via transtympanic access to the middle ear can not only avoid a postauricular incision, but, in preserving mucosa and mastoid air cells, they can participate in gas exchange and avoid the formation of extensive granulation tissue. ^, While lower rates of chorda tympani transection and scutum removal have been reported in endoscopic stapes surgery, removal of the scutum and adjacent canal wall are frequently necessary for cholesteatoma. Higher ossicular preservation rates have been reported in TEES: Tarabichi et al. were able to conserve the ossicles in 33% of their series of epitympanic cholesteatoma, and Marchioni et al. did so in over half. In Marchioni’s series, all patients who had only one epitympanic subsite involved were able to achieve ossicular preservation, with decreasing percentages and an increasing number of epitympanic subsites. Cholesteatoma involving the medial attic was the site most associated with having to sacrifice the ossicles; the authors maintain that visualization is difficult even with a 45-degree endoscope. In microscopic cases, ossicular sacrifice would be necessary in all cases of anterior attic cholesteatoma, but not in TEES.

In attempts to spare patients an invasive second look, some have advocated for making a small stab incision in a prior postauricular scar and using an endoscope to survey the prior resection bed. If significant disease is found, conversion to an open approach is performed. ^, This technique may not work well in the pediatric population given the propensity for bony regrowth and formation of scar tissue in the mastoidectomy bed. Others have advocated performing second-look procedures with an endoscope through a myringotomy to good effect. ^,

Endoscopy Facilitates Ossicular Prosthesis Placement

Due to the wider field of view offered by otoendoscopy, it is our opinion that ossicular mobility is better assessed with the endoscope, and that measuring and placing ossicular prostheses endoscopically may enhance accuracy ( Fig. 19.1 ).

TEES has Educational and Workflow Value

While no formal investigation as to the educational value of TEES has been performed, it is worth mentioning that both trainees and assistants alike have a common, high-definition, magnified view of the operative field as the primary surgeon sees it. This may facilitate more efficient learning on the part of the trainee and better anticipation of which instruments are to be used by the surgical technologist.