Chapter 2 Canalplasty for Exostoses of the External Auditory Canal and Miscellaneous Auditory Canal Problems

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Although clinical disease caused by exostoses of the external auditory canal (EAC) is infrequent, it occurs often enough that a method of surgical management should be in the armamentarium of the otologic surgeon. Because it is not a high-incidence problem or one that is life-threatening, many otolaryngologists use various independent approaches, which frequently result in elimination of or damage to the canal skin. These procedures frequently produce suboptimal results. A well-conceived approach addresses the problem of removal of exostoses, while maintaining the valuable residual skin of the EAC. This chapter begins with clinical observations regarding this condition and then describes an operative procedure that has been very successful in its management.

The etiology of these benign growths of the tympanic bone is strongly associated with the frequency and severity of exposure to cold water.¹ Frequently, these lesions are found in surfers, swimmers, or other individuals with frequent cold water exposure over several years. A widely held belief based on clinical information is that exostoses occur primarily during the years of growth, with their proliferation being enhanced or perhaps even caused by exposure to cold water during this period. This belief tends to be supported by historical information from patients with exostoses, who almost always indicate that they swam in cold water during their youth.^2–4 This historical information is strongly corroborated by the high incidence of exostoses in avid surfers who spend hours in the water almost daily. In our clinical experience, this problem occurs almost exclusively in men, who are more likely than women of the same age to have had frequent cold water exposure during their youth.

Most exostoses do not develop to a degree sufficient to cause clinical symptoms. Patients are frequently referred to otologists because the growths are observed, and not understood, by primary care physicians. This is particularly true with exostoses that have a more pedunculated form than the more subtle sessile configuration. When exostoses become more marked, however, they obstruct the natural elimination of desquamated epithelium from the ear canal, and patients usually present with recurrent episodes of external otitis. In their most prolific expression, exostoses can lead to hearing impairment by causing the collection of epithelial debris that tamponades tympanic membrane movement, by impinging on and limiting the mobility of the malleus, or by markedly narrowing the aperture of the canal. These conditions may manifest as a conductive hearing impairment on audiometric examination.

The EAC is part of the hearing pathway. Essentially, the EAC is a tube with resonant characteristics that amplify the incoming sound. The degree of amplification and the frequency at which it occurs are a function of the diameter and the length of the canal. When the diameter becomes small, it can interfere with the passage of sound and cause a hearing impairment. This effect does not become significant, however, until the aperture becomes very small. With apertures less than 3 mm, high-frequency sounds begin to diminish, and further compromise of the channel diameter results in increased impairment and lower frequency loss.

EXOSTOSES OF THE EXTERNAL AUDITORY CANAL

Surgical Indications

Surgery is indicated when chronic or recurrent external otitis exists, or a conductive hearing impairment develops. The presence of chronic and recurrent infection over an extended period seems to debilitate the canal skin, and can compromise the skin’s ability to re-epithelialize in a robust and healthy manner in the postoperative period. For this reason, surgical therapy should be considered when a pattern of recurrent external otitis has been established in these patients. Patients who have significant external canal exostoses without recurrent infection or hearing impairment should be observed periodically, and surgery should be avoided until these symptoms occur.

Preoperative Preparation

Patient Preparation

There are two components of patient preparation for otologic surgery performed under local anesthesia: psychological and pharmacologic.

Psychological Preparation

To reduce anxiety and create rapport, the surgeon should provide the patient with a full explanation of the procedure and its objectives, benefits, and risks. In addition, a surgical nurse or medical assistant should explain what will happen to the patient in the operating room, and describe such things as the operating room environment, use of an intravenous line for medication delivery, placement of monitor electrodes, and draping. By informing the patient of these things and making him or her part of the process, the clinician reduces the patient’s anxiety, encourages cooperation, and may reduce bleeding. Beyond the technical advantages achieved by such preparation, there is an ethical responsibility to inform the patient. In addition, the likelihood of the patient’s becoming litigious because of a poor result is markedly reduced if he or she has been informed about the procedure and its risks and benefits, and has had an opportunity to discuss the risks and benefits with the surgeon before the surgery.

Pharmacologic Preparation

The pharmacologic preparation of the patient can be achieved in many ways. In the average adult who selects intravenous sedation with local anesthesia, we give fentanyl, 50 to 100 μg, and midazolam (Versed), 5 to 10 mg intramuscularly 1 hour before the surgical incision. An intravenous catheter is started in the arm opposite the ear to be operated on before the patient arrives in the operating room, and 5% dextrose in Ringer solution is started with a volutrol. Unless the patient appears very sedated, an additional 50 to 100 μg dose of fentanyl is placed in the volutrol and infused slowly over 30 to 45 minutes. As the surgery proceeds, alternating supplements of intravenous midazolam and fentanyl are infused as needed to maintain sedation.

In most cases, general anesthesia is selected by either the surgeon or the patient. Patients with a history of claustrophobia, patients with poor language skills in the surgeon’s native tongue, and patients with difficult neck mobility are best approached under general endotracheal anesthesia. One advantage of use of general anesthesia is the ability to use facial nerve monitoring during the procedure. Patients receive cefazolin, 1 g intravenously, or another appropriate antibiotic 1 hour before incision.

Site Preparation

The hair is shaved behind the ear to a distance of approximately 1.5 inches posterior to the postauricular fold. The auricle and the periauricular and postauricular areas are scrubbed with povidone-iodine (Betadine) solution or chlorhexidine gluconate (Hibiclens) for iodine-allergic patients. A plastic drape is placed over the area with the auricle and the postauricular area exteriorized through the opening in the drape. This drape is placed over an L-shaped bar that is fixed in the rail attachment of the operating table (Fig. 2-1). For patients under local anesthesia with sedation, a small, low-volume office fan is attached to the bar to provide a gentle cooling breeze to the patient’s face during the procedure. The plastic drape forms a canopy, allowing the patient to see from under the drape and reducing the feeling of claustrophobia. In addition, a foam earpiece from an insert speaker is put into the opposite ear. The earpiece is connected to a compact disk player and input microphone that allows the patient to listen to relaxing music and provides a pathway to converse with the patient, if desired.

FIGURE 2-1

Analgesia

It is important not only to achieve analgesia, but also to maximize canal hemostasis with injections into the external auditory meatus. Using 2% lidocaine (Xylocaine) with 1:20,000 epinephrine solution in a ringed syringe with a 27 gauge needle, a classic quadratic injection is made such that each injection falls within the wheal of the previous injection. Another useful injection is an anterior canal injection, which is made with the bevel of the needle parallel to the bony wall of the external meatus (Fig. 2-2). In a patient with extensive exostoses, this injection is usually made into the lateral base of a large anterior sessile osteoma. After insinuation of the needle, it is advanced a few millimeters, and a few drops are injected extremely slowly. The solution infiltrates medially along the anterior canal wall and provides some analgesia to the auriculotemporal branch of CN V, which is usually unaffected by the quadratic injection and adds to the hemostasis anteriorly. The postauricular area is infiltrated with 2% lidocaine with 1:100,000 epinephrine solution mixed with equal parts of 0.5% bupivacaine.

Surgical Technique

Most surgical approaches for removal of EAC exostoses are through the transmeatal route.^5–7

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