Grayson Cole Gulf Coast Veterinary Specialists, Houston, TX, USA A total ear canal ablation (TECA) refers to complete removal of the external ear canal. As there is no longer an egress for the middle ear, this surgery requires the evacuation of diseased tissue, fluid, and epithelium from the middle ear within the osseous tympanic bulla. The middle ear procedure most often performed adjunctly with the TECA is a lateral bulla osteotomy (LBO). The procedure will be referred to as total ear canal ablation and lateral bulla osteotomy (TECA‐LBO) for the remainder of the chapter. The most common indications for TECA‐LBO are severe or end‐stage otitis externa and neoplasia or polyps of the external ear canal. In many cases, the lumen of the ear canal is completely obliterated, rendering the likelihood of successful medical management unlikely (Figure 10.1). Less common indications include otitis media, neoplasia near to the ear canal, such that an appropriate margin would include the ear canal, trauma to the ear canal, such as rupture or avulsion, congenital anomalies of the ear, such as a patulous eustachian tube, stenotic canal, or segmental external auditory canal atresia.1 A TECA‐LBO could also be considered to utilize the skin of the pinna for facial wound reconstruction2 (Figure 10.2) or for severe disease of the parotid salivary gland in which dissection results in denuding of the external ear canal. Finally, it is the treatment of choice for ears that have failed less invasive procedures, such as a lateral ear canal resection. As with any procedure requiring general anesthesia, a minimum database (e.g., complete blood cell count and serum chemistry) is recommended prior to the procedure. Thoracic radiographs are indicated for geriatric patients or patients for which neoplasia is a differential diagnosis for their ear disease. Patients with the significant systemic disease should be worked up and treated prior to surgery due to the elective nature of TECA‐LBO, except for certain trauma cases, which require more immediate surgical intervention. The gold standard of diagnostic imaging for the tympanic bulla is computed tomography (CT); however, it is feasible to perform TECA‐LBO without imaging of the bulla or with guidance from open‐mouth bulla radiography, magnetic resonance imaging (MRI), or video‐otoscopy. Cross‐sectional imaging is especially helpful in cases of suspected or confirmed neoplasia due to the ability to determine if the disease has led to rupture of the external or middle ear and to evaluate local lymph nodes. CT can be helpful for surgical planning, especially when disease exists outside of the confines of the external and middle ear (Figure 10.3). Figure 10.1 Dorsal is at the top of the image and the rostral is to the left of the image. An end‐stage ear with no appreciable opening to the external ear canal. Figure 10.2 Dorsal is at the top of the image and the rostral is to the left of the image. An image of a dog who underwent a left TECA‐LBO and then a left pinna flap to reconstruct a wound on the side of the face. Infection can also result in rupture of the external ear or lysis of the tympanic bulla, which can increase the difficulty of the procedure. It can also be helpful to evaluate the contralateral middle ear, which allows the clinician to inform the client of future treatment recommendations if indicated. Figure 10.3 An axial CT image of a dog diagnosed with ceruminous gland adenocarcinoma. Note the extent of the disease ventral to the right bulla (red star). For patients with chronic or recurrent otitis, a common consideration is whether to continue medical management or to proceed with surgery. Consultation with a board‐certified veterinary dermatologist is often helpful in determining the likely success of future medical management, as well as obtaining diagnostic information in the form of video‐otoscopic images, culture, cytology, histopathology, and CT of the bulla(e) prior to surgery. Ultimately, the decision to proceed with surgery or continued medical management is best made by the client after a thorough explanation of the risks of and postoperative care required from surgery, the at‐home care required with either route, and prognosis of medical compared with surgical management. In the author’s experience, ears that may not appear obviously end‐stage on otic exam may still fail medical management, or the client may reach a point of not being able to administer topical medication to their pet’s external ear canal due to the patient’s temperament. Delaying surgery to meet specific criteria, such as palpable canal mineralization or stenosis, is often not in the best interest of the patient or client. Once surgical management is elected, another consideration is whether to perform TECA‐LBO or other reported surgical procedures, such as lateral wall resection (LWR) or ventral bulla osteotomy (VBO). A LWR procedure does not treat the underlying cause of otitis (typically, atopy) and may need to be converted to TECA‐LBO in the future. Therefore, the procedure is rarely indicated. A possible indication would be benign neoplasia with no history of significant ear infection in which a resection with an appropriate margin can be performed with LWR. In the author’s opinion, the benefit of the LWR procedure most often does not outweigh the risk of the need to perform yet another surgery to convert to TECA‐LBO and will not be discussed further. A VBO is indicated in cases in which there is middle ear disease but no significant external ear pathology. Again, consultation with a board‐certified veterinary dermatologist can be pivotal in making the decision between TECA‐LBO and VBO in cases that have primarily middle ear pathology. VBO as a solo procedure should be reserved for patients without external ear pathology. Brachycephalic patients offer unique challenges in the execution of TECA‐LBO. Pharyngeal swelling can occur after TECA‐LBO, which can further compromise the already abnormal airways of brachycephalic patients. Although bilateral single‐session TECA‐LBO is a commonly performed and generally well‐tolerated procedure in meso‐ or dolichocephalic breeds,3 the author does not perform bilateral single‐session TECA‐LBO in brachycephalic breeds with respiratory clinical signs who have not already undergone airway surgery, primarily due to the concern for postoperative airway compromise. In the author’s experience, combining upper airway surgery with unilateral TECA‐LBO, followed by the contralateral TECA‐LBO at least four weeks postoperatively or aggressive medical management supervised by a board‐certified veterinary dermatologist, is a preferred and anecdotally successful strategy. In addition to concerns regarding postoperative upper airway obstruction, the skull anatomy of the brachycephalic dog can make the approach to the LBO more challenging than that of meso‐ or dolichocephalic skulls, as the ostium is often obscured by the mandible. Utilization of a burr or Kerrison rongeurs can be helpful to accomplish the surgery through this approach in the author’s experience. If the approach to the LBO does not yield appropriate visualization, a TECA can be combined with a VBO. Alternatively, bulla endoscopy can be performed to improve middle ear visualization intra‐operatively.4 To the author’s knowledge, no specific literature on TECA‐LBO in brachycephalic cats exists; however, similar concerns would apply for postoperative pharyngeal swelling. The surgeon should be prepared to perform a temporary tracheostomy on any postoperative TECA‐LBO patient; however, this will be more commonly indicated in brachycephalic patients. Regardless of the breed and laterality of the procedure, the same goals remain: to completely remove all of the external ear canal and to debride the middle ear to prevent a chronic draining tract and recurrent infection. A full discussion of appropriate anesthesia and analgesia techniques is outside the scope of this chapter. However, a premedication with a full mu agonist opioid is appropriate with intra‐ and postoperative opioid administration, either through continuous rate infusion (CRI) or boluses. The surgery can be stimulating and painful; therefore, the use of lidocaine or ketamine CRIs can also be used for their minimal alveolar concentration (MAC) sparing effects and for additional analgesia. A preoperative greater auricular and auriculotemporal nerve block can also be performed for intra‐operative and postoperative analgesia.5 Current research at the author’s institution is evaluating these nerve blocks with liposome‐encapsulated bupivacaine to provide up to 72 hours of analgesia. These results are pending; however, anecdotal experience is encouraging. The most common reports of TECA‐LBO are in the dog and cat. Other species that have been reported in the veterinary literature include rabbits,6 chinchillas,7 harbor seals,8 and North American bison.9 The author has anecdotal experience of performing a TECA‐LBO in an ocelot, which did not differ significantly from the procedure in a domestic cat. Several different skin incisions have been described for TECA‐LBO procedures. In dogs, a T‐shaped skin incision has been described. With this technique, an incision is made circumferentially around the external auditory meatus. In addition, a linear incision is made from dorsal to ventral at the level of the palpable vertical ear canal. An alternative is to simply make a circumferential incision around the external auditory meatus. As per the author’s opinion, this provides adequate exposure of the external ear canal and avoids both the need to make an additional incision and the perils of closing a T‐shaped incision (Figure 10.4). In cats, a U‐shaped incision has been reported in an effort to restore symmetry to the ear carriage after surgery (for unilateral TECA‐LBO).10 In the author’s experience, a simple circumferential incision works well for cats, too. Figure 10.4 A circumferential incision is made around the external auditory meatus through the skin, thin subcutaneous layer, and cartilage. The auricular muscles will need to be transected circumferentially around the external ear canal. This can be accomplished with blunt or sharp dissection or with monopolar electrosurgery (Figure 10.5). There is often increased vasculature in chronically infected or neoplastic ears, so dissection with monopolar cautery is helpful to alleviate hemorrhage. Grasping the external ear canal with an Allis tissue forceps after establishing a dissection plane between the perichondrium and auricular muscle attachments can be helpful for counter‐traction during the procedure. Some surgeons utilize a Lone Star retractor or two small‐tipped Gelpi retractors placed perpendicular to each other during this portion of the procedure. The author prefers a surgical assistant and a Senn retractor due to the frequency in which the retraction requires adjustment as the dissection proceeds from superficial to deep toward the bulla. Due to concern for damage to the facial nerve from the thermal spread of monopolar cautery, the author discontinues monopolar cautery after dissection of the vertical canal once the cartilage changes from auricular to annular with the horizontal canal. For continued external ear canal dissection between the cartilage and muscular insertions, sharp dissection with tenotomy scissors with curved tips pointing toward the ear canal and taking tiny bites in a circumferential trajectory combined with bipolar cautery for hemostasis when needed is preferred by the author (Figure 10.6). The facial nerve exits the stylomastoid foramen and becomes visible during the TECA‐LBO procedure caudal and ventral to the external ear canal near the junction between the vertical and horizontal canals (Figure 10.7). In chronically inflamed ears, the facial nerve may be adhered to the ear canal and require gentle dissection of the cartilage prior to ear canal transection. Figure 10.5 Dorsal is at the top of the image and the rostral is to the right of the image. The auricular musculature is dissected from the vertical ear canal. Figure 10.6 Dorsal is at the top of the image and the rostral is to the right of the image. Dissection with tenotomy scissors at the insertion of the auricular muscles onto the external ear canal. A Senn retractor is being used to provide visualization. Figure 10.7 Dorsal is at the top of the image and rostral is to the right of the image. The facial nerve can be seen caudal and ventral to the ear canal, between the two instruments.
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Total Ear Canal Ablation and Lateral Bulla Osteotomy (TECA‐LBO)
Introduction
Indications and Pre‐operative Considerations
Surgical Procedure
Skin Incision
Auricular Muscle Dissection
External Ear Transection
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