10 Problems and Solutions in Middle Ear Cholesteatoma Surgery
10.1 Labyrinthine Fistula
In our experience, labyrinthine fistulas complicate about 10% of cholesteatomas we operated on (▶Fig. 10.1). In all cases of cholesteatoma, the presence of a labyrinthine fistula should be assumed during surgery until its absence is verified. Lack of any inner ear symptom or signs of a fistula does not mean that the labyrinth is intact. The lateral semicircular canal, located superficially in the vicinity of the attic, is the site most commonly involved (▶Fig. 10.2 ).
The choice between canal wall down or up technique, depends mainly on how far the disease has extended and the size of the mastoid (see Indications in Chapters 6 and 7). When canal wall down technique is used, it is better to leave the matrix on the fistula to avoid postoperative labyrinthitis. Therefore, according to our strategy in which the closed technique is used only in limited numbers of cases, the posterior wall is usually removed and the matrix is left in place. If the extent of the disease and the status of the mastoid allow the closed technique to be used, treatment of a labyrinthine fistula depends on its size. In many cases, the fistula is already large (> 2 mm) at the time of operation. In such cases and those with fistulas in the ear with better hearing, canal wall down techniques are indicated and the cholesteatoma matrix is left over the fistula, to avoid deaf ear (▶Fig. 10.3, ▶Fig. 10.4, ▶Fig. 10.5). In canal wall down tympanoplasty, since the fistula is exteriorized in the cavity with the matrix left in place, second-stage surgery for the fistula is not necessary.
Cholesteatoma with fistulas smaller than 2 mm may be treated with canal wall up techniques. When canal wall up technique is used, management of the fistula depends on its size. If the matrix is cut with a sufficient margin, the matrix covering the fistula is isolated from the surrounding area, and most of the cholesteatoma is dissected from the middle ear. To avoid keeping the inner ear open for a long time, further management on the fistula should be performed at the end of surgery when all the reconstructions are completed and materials to cover the fistula are available. If the fistula is less than 1 mm in size, the matrix covering the fistula can be removed. Blunt dissection of the matrix is done carefully with a microdissector and a small cottonoid under continuous suction irrigation (▶Fig. 10.6). The opening in the labyrinth (▶Fig. 10.7) should immediately be closed with bone paste, and the area covered with a piece of either temporal fascia or perichondrium (▶Fig. 10.8, ▶Fig. 10.9). If the matrix is adherent to the membranous labyrinth or the fistula is larger than 1 mm, the matrix is left in place, even in canal wall up technique. To reduce the epidermis and to interrupt its possible nutrient pathways, the matrix is trimmed with a sharp knife, leaving a small matrix that is less than 1 mm larger than the margin of the fistula. Meticulous care should be taken not to enter the labyrinth. If the labyrinth is entered, the matrix is removed and the fistula is managed as described above. If the canal wall up technique is implemented, second-stage surgery should be planned within 6 months. In our experience, the epidermis left over the fistula in closed technique disappears in 70% of cases, or in the remainder forms an easy-to-remove pearl at the second stage (▶Fig. 10.10).
In some cases, the fistulas get local inflammation that lead to closure of the semicircular canal with fibrosis. Removal of the matrix is possible in such cases even when the fistula is large. The condition can be diagnosed preoperatively with heavily T2-weighted magnetic resonance imaging (MRI). Another case of safe removal of the skin from large labyrinthine fistula is a thick coverage over it. In such condition, the surgeon can remove only the superficial part of its coverage using sharp scissors, and removal of skin without entering the labyrinth is achieved. In such cases, the area of the fistula can be covered with bone paste to reduce possibility of labyrinthitis.
10.2 Bone Erosion in the Tegmen
Bone erosion in the tegmen is seen frequently in cholesteatoma surgery. It may eventually cause meningoencephalic herniation (see Chapter 10.5). Patients with meningoencephalic herniation have a high risk of liquorrhea, meningitis, and epilepsy caused by an epileptogenic focus in the herniating brain tissue. Since the presence of both the erosion in the tegmen and labyrinthine fistulas usually mean progression of destructive process in the attic and the antrum, they often complicated with each other. In such cases, management of both complications simultaneously is required.
To prevent these complications, large erosions should be repaired with cartilage and bone paste, and the area covered with fascia. If a small area of the middle cranial fossa dura is exposed but not protrude into the canal wall up cavity, it can be left in place. If it is seen in the canal wall down cavity, a pedicled subcutaneous tissue flap may be harvested (from beneath the concha cartilage during the later meatoplasty) and placed over that area.