Operative Technique

Once the patient is prepped and draped, local injection should be performed with 1 to 2% lidocaine with 1:100,000 dilution epinephrine for vasoconstriction. A postauricular injection should be made in the postauricular crease, extending from the superior-most aspect of the auricle to the mastoid tip. Care should be taken not to extend the injection beyond the mastoid tip, because temporary paresis of the facial nerve can occur. If meatal injections are required, they should be performed in all four quadrants of the external auditory canal. Local anesthetic should be injected at the bony-cartilaginous junction while pressure is applied laterally with an ear speculum. A blanch should be apparent extending toward the tympanic membrane if the injection is performed properly.

After vasoconstriction has occurred, and canal incisions have been made if necessary, the postauri-

cular incision should be made. The incision should begin at the superiormost aspect of the auricle in the postauricular crease; it should be carried inferiorly either in the postauricular crease or up to 1 cm posterior to it. The incision should extend to the mastoid tip, but not beyond it due to risk of injury to the facial nerve. In children, the course of the facial nerve exiting the stylomastoid foramen can be quite lateral; therefore, the postauricular incision should be shifted posteriorly.8 The No. 15 blade should be used to make the incision. The blade should be used to carry the incision down to the level of the temporalis fascia. Blunt dissection with a finger should be easily accomplished in this plane to elevate flaps anteriorly and posteriorly. Monopolar cautery is used to control bleeding.

A cerebellar retractor is then placed to retract the ear anteriorly. If a graft is needed for tympanoplasty, now is the time to harvest one. The loose areolar tissue overlying the temporalis fascia posterosuper-ior to the auricle is elevated by injecting deep to it with local anesthetic. The No. 15 blade is then used to begin an incision through the tissue, and the Metzenbaum scissors and a tissue forceps are then used to harvest a generous-size graft, approximately 1 cm2 in area. The graft is then placed on a heated block and flattened with the back end of a forceps or knife handle, and left to dry.

The monopolar cautery is then used to incise the temporalis fascia along the linea temporalis, extending from the zygomatic root posteriorly. The incision is carried down through the periosteum to the temporal bone itself. A vertical T incision is then

Temporalis Muscle Flap Technique

muscle incision

FIGURE 8 — 1 Exposure of the mastoid cortex.

muscle incision

FIGURE 8 — 1 Exposure of the mastoid cortex.

made connecting the horizontal incision to the mastoid tip. It is important during this step to leave a sizable flap anteriorly to facilitate closure of the periosteum at the end of the procedure.

The periosteum is then elevated anteriorly, posteriorly, and superiorly with a heavy Lempert elevator until the entire mastoid cortex is exposed. Bleeding from emissaries may be controlled either with cautery or with bone wax. The cerebellar retractors are then repositioned to retract the periosteum (Fig. 8-1).

The operating microscope is then positioned such that the mastoid cortex is in view. A low-power lens should be used to visualize the entire cortex, external auditory canal, and linea temporalis for orientation during dissection. A large suction irrigator and large cutting bur are used initially to make the first cuts in the mastoid cortex. The initial cuts are made posteriorly along the linea temporalis, and inferiorly along the border of the external auditory canal extending into the mastoid tip.

Dissection should begin at the zygomatic root, at the apex of the two initial cuts. The large cutting bur should be used to extend the dissection posteriorly and inferiorly, keeping the dissection at the same depth throughout the mastoid cavity to facilitate identification of landmarks. Cuts should be made parallel to the linea temporalis and external auditory canal; the bur should also be swept posteriorly along the inferior border of the mastoid as well (Figs. 8-2 and 8-3).

During dissection, the direction of the cuts should parallel the underlying structures to be identified. When locating the tegmen tympani, the cuts should

Chorda Tympani Tympanic MembraneIdentifying Landmarks Tympanic Membrane
FIGURE 8—3 Exposure of the mastoid tip.

be parallel and inferior to the linea temporalis to avoid injury to the underlying dura. Likewise, the sigmoid sinus is best identified sweeping posteriorly along the inferior border of the mastoid, then carrying the dissection superiorly parallel to the

Sinodural Angle

FIGURE 8—4 Tegmen tympani, sigmoid sinus, and sinodural angle.

Sinodural Angle
intact

FIGURE 8—5 Exposure of the mastoid portion of the facial nerve.

initial cut (Fig. 8—4). Finally, the horizontal semicircular canal should be identified by sweeping posteriorly along the border of the external auditory canal (EAC). This method avoids transection of important structures.

Once Korner's septum has been entered and the tegmen tympani, sigmoid sinus, and horizontal canal have been identified, dissection should then be focused on defining the sinodural angle and the

Omer mastoid bone and facial recess and cells

Omer mastoid bone and facial recess and cells

Sinodural Angle

FIGURE 8—6 Completed canal-wall-up mastoidectomy with facial recess.

Chorda Tympani Tympanic Membrane

antral air cell. The surgeon should ensure that the tegmen is identified along the entire course of the linea temporalis to facilitate exposure of the antrum and fossa incudis.

The antral air cell should be identified by drilling anteriorly and superiorly at the apex of the first two bur cuts, near the root of the zygoma. At this point during the dissection, the surgeon may wish to change to a smaller cutting bur to better define the antrum. Alternatively, a curette may be used. The drill should be placed medially and pulled laterally to protect the underlying structures. The surgeon should take care not to form ledges or overhanging bone particularly at this stage, as this may contribute to inadvertent injury. The bed may also be rotated away from the surgeon and the microscope reposi-tioned to provide better visualization of the incus.

once the fossa incudis and the incus have been identified, a diamond bur should be used to control any bleeding from the mastoid bone and to smooth out any rough areas remaining along the tegmen or the posterior wall of the EAC. The facial nerve should now be identified using a large diamond bur. The level of the nerve will be marked by the incus and the horizontal canal. The nerve should be identified by gently passing the drill anterior and

Middle Ear Mastoid Surgery

MIDDLE EAR AND MASTOID SURGERY

parallel to the sigmoid sinus, then moving anteriorly. The distinct appearance of the facial nerve and the chorda tympani will appear along the posterior aspect of the EAC, coursing inferiorly (Fig. 8-5).

The facial recess is now ready to be opened if necessary. The landmarks have been identified, including the fossa incudis, chorda tympani, and mastoid portion of the facial nerve. Either a diamond bur or a cutting bur may be used to open the recess. Again, the largest bur possible should be used for this portion of the procedure. The mastoid bone and facial recess air cells are entered, taking care to avoid injury to the facial nerve by making cuts parallel to its course. Drilling is continued until the middle ear space is entered (Figs. 8-6, 8-7, and 8-8). Work in the middle ear can now be accomplished if necessary, and tympanoplasty can be carried out using standard techniques.9

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