6 Canal Wall Up Tympanoplasty
Indications
Following are the indications for canal wall up tympanoplasty:
Cholesteatoma in children and in patients with highly pneumatized mastoids.
Minor epitympanic erosion.
Mesotympanic cholesteatoma.
There is no single procedure to treat all cases of cholesteatoma. The surgeon should be flexible and well prepared to choose a surgical technique suitable for the particular patient. Whenever a minor epitympanic erosion is present, we adopt a canal wall up (CWU) (closed) technique with reconstruction of the attic using cartilage and bone paste. In general, we use canal wall down (CWD) (open) tympanoplasty in most cases of cholesteatoma, since CWU technique results in higher residual (▶Fig. 6.1) and recurrent (▶Fig. 6.2) rate compared to the CWD technique. Surgical intervention for cholesteatoma using CWU tympanoplasty should be completed by the second-stage operation, since the objective of the surgery is not only to reconstruct the sound transmission system, but also to eradicate any residual cholesteatoma. Currently, we use closed technique only in selected cases.
In patients with highly pneumatized mastoid, CWU tympanoplasty is also indicated to avoid having a very large cavity. In children, we try to perform a staged CWU tympanoplasty because of their highly cellular mastoids and in an attempt to preserve the anatomy of the ear as much as possible. However, even in such cases, if there is large epitympanic erosion or surgery reveals intensive involvement of the middle ear by cholesteatoma, we use the CWD technique. CWD tympanoplasty is also chosen for the only hearing ear. In the presence of mesotympanic cholesteatoma, especially in young patients, closed tympanoplasty may be indicated. In the first operation, a CWU tympanoplasty is performed with reconstruction of the tympanic membrane, and a Silastic sheet is placed through a posterior tympanotomy toward the eustachian tube to cover both the tympanic cavity and the mastoid. Silastic favors regeneration of the middle ear mucosa and prevents the formation of adhesions. However, if the posterior wall interferes with the view of the cholesteatoma matrix, for example, by extension toward the eustachian tube, open tympanoplasty is adopted, especially in old patients.
If the surgeon is not sure whether removal of the posterior canal wall is suitable, every surgical step is performed as CWU tympanoplasty. Once it turns out that CWD tympanoplasty is indicated, conversion of the technique by removing the posterior wall is not a major effort. Time spent in canalplasty and tympanotomies is worthwhile for the patient.
In the second stage, usually performed 8 to 12 months later, the middle ear is checked for eradication of any residual cholesteatoma. The approach for the second stage is transmeatal, transcanal, or transmastoid, depending on the localization of the cholesteatoma and approach used in primary surgery. If a recurrent cholesteatoma or absorption of the posterior canal wall is encountered in the second stage, we transform the technique into CWD without hesitation.
Postoperatively, regular otoscopic follow-up, for at least 10 years, is essential to identify the formation of a retraction pocket or recurrent cholesteatoma. If these occur, there should be no hesitation in switching to a CWD tympanoplasty, since we believe that they indicate a persistent underlying pathology, even after the earlier CWU tympanoplasty.
6.1 Surgical Steps
6.1.1 Simple Mastoidectomy
The technique used for mastoidectomy in CWU tympanoplasty should be the same as CWD tympanoplasty. The only difference from the CWD technique is a preservation of posterior canal wall. Adequate saucerization of the mastoid cavity with complete drilling of the sinodural angle and bony overhang at cavity edges should be carried out before posterior epitympanotomy and posterior tympanotomy is performed. The saucerized cavity gives the maximum surgical view and surgical angle (▶Fig. 6.3, ▶Fig. 6.4). Canalplasty is required whenever the canal wall impedes a complete view of the tympanic membrane. Therefore, the canal wall should not be thinned from the beginning.
The meatal skin flap is elevated medially and the canalplasty is performed. For better control of any pathology and to facilitate reconstruction, it is important that the extent of canalplasty performed allows a complete view of the entire annulus without moving the microscope.
6.1.2 Posterior Epitympanotomy
The attic is opened from behind, keeping the superior canal wall intact. Drilling of this area should be conducted from medial to lateral (▶Fig. 6.5, ▶Fig. 6.6). Inattentive drilling with a burr inserted into the attic easily insult the incus located behind the bone (▶Fig. 6.7). It is important to recognize that the short process of the incus is closer to the surgeon than its body, and the short process is very close to the bone covering it (▶Fig. 6.8). The posterior atticotomy should have enough anterior extension to control the whole attic completely. The final bony overhang covering the incus may be removed with a curette (▶Fig. 6.9). For early identification of the incus, it is very important to shift visual axis more posteriorly by rotating the bed away from the surgeon after opening the sinodural angle sufficiently.
The area is limited superiorly by the middle cranial fossa dura, inferiorly by the canal wall, and medially by the ossicular chain. The utmost care should be taken not to touch the ossicular chain with the burr when the chain remains intact. If there is a risk, the incudostapedial joint should be disarticulated first. In this case, reconstruction of the ossicular chain may be performed either at the end of the surgery or in the second-stage operation, depending on the pathology.
Care should be taken not to fenestrate the superior wall of the external auditory canal. If it occurs, reconstruction with cartilage and bone pâté is necessary. Care should be taken not to injure the middle fossa dura. The dura is very fragile especially in the elderly, and cerebrospinal fluid (CSF) leak may follow. In addition, exposure of the middle fossa dura may cause meningoencephalic herniation. To avoid excessive removal of the bone, never press the burr heads against superior (middle fossa plate) and inferior (superior meatal wall) bony walls in this area.
A retraction pocket with small epitympanic erosion may be dissected and pushed out to the external auditory canal from the attic cavity with a small cottonoid (▶Fig. 6.10). In order to ventilate the epitympanum via the anterior epitympanum, the overhanging cog is removed either with a curette or with a burr after the malleus head is mobilized.
In case of attic cholesteatoma extending into the anterior epitympanum, the incus is removed and the head of the malleus is cut, and the cog is removed with either a burr or a curette to open the anterior epitympanum.
In cases with both retraction pocket and attic cholesteatoma, sufficient removal of the lateral attic wall that impedes complete access to the entire attic is important to avoid leaving epidermis in the middle ear. However, to reduce the possibility of cholesteatoma recurring, a very large atticotomy should be avoided.
6.1.3 Posterior Tympanotomy
The posterior wall of the external auditory canal is thinned out. The final step is preferably carried out with a large diamond burr. It is important not to make the posterior canal wall too thin. Inadvertent opening or postoperative atrophy of the canal wall can lead to recurrent cholesteatoma, even after a considerable time, if tubal function is impaired.
To avoid facial nerve injury, positive identification of the facial nerve is valuable. The third portion of the facial nerve is identified using a large cutting burr, moved parallel to the course of the nerve, with continuous suction and ample irrigation. The nerve is only skeletonized, never exposed. Care should be taken not to open the lateral semicircular canal that is located just posterolateral to the facial nerve. The chorda tympani should also be identified.
Using a diamond burr or a curette, the facial recess between the facial nerve and the chorda tympani is opened (▶Fig. 6.11). The chordal crest can be seen in this step (see ▶Fig. 1.13). If the ossicular chain remains intact, a small buttress of bone may be left intact posterior to the short process of the incus to protect the chain from the burr.
The size of posterior tympanotomy depends on how far the pathology has extended to the facial recess and the sinus tympani. Opening between the facial nerve and the chorda tympani is usually sufficient to control the area of the incudostapedial joint and the oval window (▶Fig. 6.12). If the round window and/or hypotympanum should be managed, the posterior tympanotomy may be extended inferiorly after transecting the chorda tympani (▶Fig. 6.13, ▶Fig. 6.14).
6.1.4 Middle Ear Management
General Considerations
The tympanomeatal flap is elevated with the posterior annulus. The middle ear is explored through both posterior tympanotomy and the external auditory canal.
It is better to finish management of the middle ear as soon as possible. In this way, complete hemostasis is achieved before reconstruction. On the other hand, management of the oval and round window areas is conducted after completing bone work. The surgeon should find right moment to complete middle ear management in each surgical operation.
The pathology is dissected from the middle ear, taking care not to damage the fragile structures.
Dissection of pathology from fragile structures in the tympanic cavity is carried out in a combined approach, with one instrument introduced from the external auditory canal and the other from the posterior cavity (▶Fig. 6.15). In this way, even though two required instruments are introduced simultaneously into the restricted area, the narrow view of delicate structures, through either tympanotomies or the meatus, is not obstructed by the instruments.
The tympanic membrane and the ossicles may be removed depending on the lesion. The tympanic membrane is repaired using the temporalis fascia if some defect or a perforation exists.
Cholesteatoma Removal
Dissection of cholesteatoma starts with removal of its debris, leaving the intact matrix in place (▶Fig. 6.16). In this way, the structures under the cholesteatoma are seen either directly or through the matrix before completely elevating the matrix, and the dissection can be carried out more safely.
To leave matrix as intact as possible, a blunt dissection of the matrix with the help of cottonoids and a suction tip is carried out (▶Fig. 6.17).
Antrum and Attic
Absence of labyrinthine fistula should be looked for carefully, especially in the area of the lateral semicircular canal (▶Fig. 6.18). A fistula can be seen through thin matrix as a bluish spot or line. If fistula is identified, or the highly suspicious area is covered with thick tissue, management of that area should be left until the final moment of the surgery (see Chapter 10).
In the antrum and the attic, the dissection is carried out with help of cottonoid, a suction tip, and the microdissectors (# 1 or #2 in ▶Fig. 3.29). The matrix is gently elevated and pushed toward the attic, and the tympanic cavity.
Oval Window
At first-stage surgery, excessive attempts at removing cholesteatoma from this area is proscribed. If there is any risk to open the vestibule, the matrix can be left over the stapes. In such cases, second-stage surgery should be planned to take place within 6 months.
Dissection of cholesteatoma from the area of the windows is started after all bone work has been completed. All maneuvers on the stapes superstructure should be carried out with extreme care. Dissection is conducted along long axis of the footplate, never perpendicular to it.
If the matrix covers the stapedius tendon, the tendon should be cut. If the matrix adheres underneath the arch of the superstructure, the superstructure is also removed with long and straight spring scissors (see ▶Fig 2.9) taking care not to fracture the footplate. Do not use crurotomy scissors. It could damage the footplate.
If the superstructure is absent, the matrix may be dissected through the meatus. Sufficient visualization of this area is the key to safe and complete removal. For this reason, position of the patient is very important. The bed should be tilted toward the surgeon and in a head-down position. Removal of a small part of the posterior canal wall might be required. Sometimes, the pyramidal eminence needs to be removed with either a small curette or a small diamond burr. The matrix is removed from the footplate from a posterior to anterior direction (▶Fig. 6.19, ▶Fig. 6.20).
Round Window
If the matrix covers the round window niche, its removal starts from the promontory or the hypotympanum with an instrument introduced through the meatus. In some case, removal of a bony overhang in the superior edge covering the niche is required.
Hypotympanum
Rarely, the hypotympanic cells are infiltrated by cholesteatoma matrix (▶Fig. 6.21). In such cases, area between the jugular bulb and the carotid artery is carefully drilled. It is preferable to start drilling with a largest possible cutting burr, since cutting burrs hardly bury cholesteatoma matrix in cells (see Chapter 4). Diamond burrs are preferred when the drilling approaches the great vessels. Great care should be taken not to damage the jugular bulb, since the structure is extremely fragile.
If there is any doubt of residual matrix, the surgery should be either staged or transferred to CWD technique with exteriorization of the hypotympanic area.
Tympanic Sinus and Posterior Mesotympanum
Dissection of cholesteatoma matrix from the tympanic sinus and posterior mesotympanum is carried out as a combined approach, working through the mastoid and the canal at the same time, with a suction tube held in one hand and a tympanic sinus hook in the other (▶Fig. 6.22). The maximum view of the bottom of the tympanic sinus is obtained through the canal, with the patient’s bed deeply tilted toward the surgeon. Nevertheless, the surgeon is usually forced to dissect in blind fashion, to some extent, medial to the facial nerve. A small cottonoid is placed between the bone and the matrix, and the matrix is detached from the bone taking care to preserve its continuity as much as possible (▶Fig. 6.23a, b).
6.1.5 Reconstruction
Every defect of the posterosuperior bony canal wall should be immediately repaired. Erosion of the superior bony annulus may be repaired with a large cartilage inserted from the posterior cavity. The cartilage may be reinforced with bone pâté. If the manubrium is present, small cut may be made in the cartilage (▶Fig. 6.24).
The cartilage is then covered from its meatal side with bone pâté mixed with blood. Reconstruction only with either autologous or homologous cartilage usually results in atrophy of the posterior wall, which may eventually cause recurrence. We always use bone pâté with cartilage for reconstruction of the canal wall. The bone pâté is further covered with a thin piece of cartilage from the canal side (Sandwich technique; ▶Fig. 6.25).
In cases with a retraction pocket in the posterosuperior quadrant, the posterior aspect of the tympanic membrane may be reinforced with a thin cartilage.
In cases of cholesteatoma, atelectasis and extensive mucosal defects in the medial wall, a medium-to-thick Silastic sheeting, sufficiently large to cover the medial wall of the middle ear including the tubal orifice, the epitympanum, the opened facial recess, and the mastoid, are inserted from the mastoid (▶Fig. 6.26). The Silastic sheeting helps to avoid adhesions between the graft and denuded tympanic wall and to promote good mucosal regeneration.
The eustachian tube, and subsequently, the tympanic cavity are packed with small pieces of Gelfoam placed over the Silastic sheeting. Any defect in the tympanic membrane should be reconstructed with the temporalis fascia.
A tympanostomy tube may be inserted in the anterosuperior quadrant in cases of tubal insufficiency.
6.1.6 Closure
The external auditory canal is packed with small pieces of Gelfoam, first anteriorly, then superiorly and inferiorly. The posterior wall is left unpacked at this stage. The self-retaining retractor is removed and folded gauze is placed on the retroauricular wound. The auricle is placed back in its position. Using a nasal speculum, the meatus of the external auditory canal is held and widened. After identifying its edge by pulling it up with forceps, the posterior meatal skin is correctly unfolded over the canal wall. The posterior wall and then entire canal are packed with Gelfoam.
In closed tympanoplasty, since there is an opening of the mastoid cavity posterior to the canal, the laterally based posterior meatal skin flap may slip into the mastoid cavity, especially when canalplasty is performed. Make sure that the posterior meatal skin is long enough to stay within the canal (▶Fig. 6.27). Short meatal skin may cause iatrogenic cholesteatoma (▶Fig. 6.28, ▶Fig. 6.29). If the skin flap is short, it should be sufficiently undermined to lengthen it, and a subcutaneous tissue flap is harvested behind the meatal skin (▶Fig. 6.30). The subcutaneous flap is interposed between the posterior bony canal wall and the skin flap to support the skin flap from behind (▶Fig. 6.31). As alternatives to this technique, the short posterior meatal skin can be sutured to the bony canal wall after creating small holes in the wall, or a thin piece of cartilage may be placed over the posterior canal wall.
The musculoperiosteal layer is held in position with a couple of sutures, and the skin is closed in two layers. We never use transmastoid drainage, since it is unnecessary and may become a source of infection.
Case 6.1 (Right Ear)
See ▶Fig. 6.32, ▶Fig. 6.33, ▶Fig. 6.34, ▶Fig. 6.35, ▶Fig. 6.36, ▶Fig. 6.37, ▶Fig. 6.38, ▶Fig. 6.39, ▶Fig. 6.40, ▶Fig. 6.41, ▶Fig. 6.42, ▶Fig. 6.43, ▶Fig. 6.44, ▶Fig. 6.45, ▶Fig. 6.46, ▶Fig. 6.47, ▶Fig. 6.48, ▶Fig. 6.49, ▶Fig. 6.50, ▶Fig. 6.51, ▶Fig. 6.52.
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