Currently most surgeons use a postauricular incision for chronic ear disease. Exposure of the anterior middle ear, mastoid cavity, and facial recess is excellent with this approach. It can also be converted to a CWD procedure with minimal difficulty. After general anesthesia is instituted, the operated ear is positioned facing up. To improve the postauricular exposure, the hair above and behind the ear may be shaved or taped down. Under the operating microscope, wax is cleaned from the ear canal. Using a 3-cc syringe with Luer-Lok and a 25- or 27-gauge needle, 1% lidocaine with 1:100,000 epinephrine is injected into the bony-cartilaginous junction. With the largest speculum that fits the ear canal pressing firmly on the bony canal, the injected solution is directed medially toward the tympanic membrane (TM). During this process of hydrodissection, steady pressure from the syringe is more important than the volume of the injectant. When the injection is properly carried out, the needle sweats with condensation and the total volume injected at all four quadrants is less than 1 cc.
Then postauricular incision is also injected. Remember that the maximum amount of lidocaine with epinephrine to be injected in a child is 7 mg/kg. In children younger than 3 years of age, the mastoid tip may not be fully developed. As the facial nerve exits the stylomastoid foramen, it is immediately deep to the subcutaneous tissue underlying the skin. To avoid injury to the nerve, the postauricular incision should be placed more posterior and away from the mastoid tip (Fig. 13-3). As the mastoid tip and tympanic ring develop, the nerve takes a deeper position. In a young adult the nerve is protected by the mastoid tip, tympanic bone, and the fascia between the parotid and cartilaginous external canal. The postauricular incision may be placed at the auriculomastoid crease (Fig. 13-4). It is a good practice to place the surgeon's finger over the mastoid tip in a child, and between the mastoid and the angle of the mandible in a young adult, to provide added protection for the facial nerve. Excessive local anesthetic injection near the mastoid tip may render the facial nerve monitor nonfunctional during the operation.
The skin and the ear are prepped with sterilizing agent while the surgeon washes his or her hands.
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