Ear

Aural hematomas occur most frequently in dogs with pendulous ears and occasionally in dogs with erect ears and in cats. Hematomas are most apparent in the concave surface of the ear. The etiology is not clear, but the most accepted theory is that the lesion is self-inflicted from head shaking, scratching, and rubbing the ear.

The auricular cartilage is pierced by many foramina, a configuration that permits passage of numerous vessels from the great auricular artery. Shearing forces from trauma are believed to tear some of the vessels. Blood accumulates between the skin and the layers of cartilage of the pinna. Bleeding continues until the internal pressure equals the pressure of the feeder arteries. The underlying causes for irritation to the ear should include all the external factors and diseases that predispose an animal to otitis externa, including immune-mediated diseases, food, and inhalant hypersensitivities.

Treatment Considerations

Hematomas should be treated immediately after diagnosis. Untreated hematomas usually cause various cosmetic alterations resulting from fibrous contracture. Some ears have a cauliflower-like appearance, which is a permanent alteration. Identification and treatment of the underlying cause are critical to long-term management of patients with aural hematoma.

Suture Technique

In my experience, incisional drainage combined with suturing has consistently been the most successful treatment for aural hematomas. The pinna is surgically prepared on both sides. Hematomas have been opened using longitudinal, S-shaped, and cruciate incisions, depending on the surgeon’s preference. I prefer the longitudinal incision, and it is not necessary to remove additional skin to widen the incision.

The fibrin clot is removed, and the cavity is curetted and flushed with saline. Horizontal mattress sutures are placed in rows parallel to the skin incision (Figure 13-1). The first row of sutures are placed at the outer edge of the hematoma cavity with each new row placed toward the skin incision. The spacing of sutures varies with the size and shape of the pinna and the size and location of the hematoma.

Mattress sutures are 5 to 10 mm wide, 5 to 10 mm apart in each row, and 5 to 10 mm between each row, and the last row of sutures is 2 to 5 mm from the skin incision. Usually, 2 to 5 rows of sutures are placed on each side of the incision. To promote wound drainage, the skin incision is not sutured. The same procedure is recommended for cats; however, the suture spacing is 2 to 4 mm apart. The sutures should not be placed perpendicular to the skin incision in either species (Figure 13-2).

The sutures penetrate the full thickness of the pinna and are tied on the convex surface of the ear (Figure 13-3). When placing the sutures, the surgeon should avoid the three main great auricular branches, which are visible on the convex surface of the pinna. Suture tension is subjective. As a guideline, sutures should be placed with just enough tension to permit insertion of the needle holder tips to the level of the hinge.

Various suture materials have been used. My preference is 2-0, 3-0, or 4-0 nylon or polypropylene swaged onto a straight cutting needle. The use of stents or suturing through material, such as radiographic film, is usually not necessary if sutures are placed properly.

Postoperative Care

A light protective bandage is applied to protect and immobilize the ear. Pendulous ears are bandaged over the head or neck. Erect ears are bandaged to maintain a normal erect position. Ear bandages should not occlude the opening of the vertical canal. The bandage is changed in 3 days and is removed in 7 days. The sutures are removed in 3 weeks. An Elizabethan collar is recommended to prevent scratching of the unband-aged ear.

Complications

The most common complications of aural hematomas are cosmetic alterations and recurrence. Necrosis of the pinna has been reported from improper suture placement. Cosmetic alterations are usually the result of delayed treatment, improper suture placement, and excessive suture tension.

Aural hematomas can recur at the same site, but they are more likely to recur adjacent to the original hematoma. Recurrence of a hematoma is likely when inadequate numbers of sutures are used or inappropriately placed or when the underlying causes of the hematoma are not identified and treated appropriately. Necrosis of the pinna can be prevented by avoiding the ascending branches of the great auricular artery through the use of suture placement parallel, rather than perpendicular, to the incision.

Client Education

Communication with the animal’s owner regarding all aspects of aural hematomas and their management will help to avoid misunderstandings, especially if complications occur. Owners should also understand that to treat the underlying causes properly, further investigation and expense will be required.

Suggested Readings

Angarano DW. Diseases of the pinna: Vet Clin North Am 1988; 18:1. Dubielzig RR, Wilson JW, Seireg AA. Pathogenesis of canine aural hematomas. J Am Vet Med Assoc 1984,185:873.

Harvey CE. Ear canal disease in the dog: medical and surgical management. J Am Vet Med Assoc 1980:177:136.

Henderson RA, Home RD. The pinna. In: Slatter DH, ed. Textbook of small animal surgery. 2nd ed. Philadelphia: WB Saunders, 1993.

McKeever PJ. Otitis externa. Compend Contin Educ Pract Vet 1996:18:759.

McCarthy RJ. Surgery of head and neck. In: Lipowitz AL, Caywood DD, Newton CD, et al, eds. Complications in small animal surgery. Baltimore: Williams & Wilkins, 1996.
 

One disadvantage of suture techniques for repair of aural hematomas is the possibility that the treated ear may thicken, wrinkle, and resemble a cauliflower. These unwanted changes do not occur with the sutureless technique described in this section.

After the pinna has been clipped, thoroughly cleaned, and prepared, an elliptic incision is made on the concave surface over the swelling. The incisions should expose the hematoma cavity from end to end. The cavity is thoroughly curetted and copiously irrigated. The ear is firmly taped so the incision is exposed (Figures 13-4 and 13-5), and the pinna is then reflected over a large roll of cast padding and is taped in place (Figure 13-6). A nonstick Telfa surgical dressing covered by a Tendersorb Wet Pruf (Ken Vet Animal Care Group, 100 Elm Street, Walpole, MA 02081) pad is applied to the incision surface and is changed as needed. Sutures are not used.

The ear is left firmly immobilized for 3 weeks. Healing is by second intention. The elimination of sutures helps to keep the pinna flat and prevents thickening, wrinkling, and cauliflowering.
 

Otitis externa is an inflammation of the epithelium of the external ear canal characterized by an increased production of ceruminous and sebaceous material, desquamation of epithelium, pruritus, and pain. The condition is caused by one or more etiologic agents including parasites, bacteria, and fungi. In addition, allergy and trauma may play a role in otitis externa. The conformation of the ear canal and that of the pinna can predispose to development of acute and chronic otitis externa. For example, the high incidence of the disease in poodles and cocker spaniels indicates that the pendulous pinna and hair-filled external ear canal predispose to otitis externa. The high relative humidity of the external ear canal, in addition to the warmth, darkness, and enclosed nature of the ear canal of some breeds of dogs, provides an excellent environment for the growth of infective agents. Chronic otitis externa can permanently change the size and character of the external ear canal. The epithelium becomes thickened and fibrous and can become ulcerated. The ear canal can become stenotic if the epithelium becomes excessively scarred or undergoes metaplastic proliferation.

Diagnosis and Medical Treatment

A complete otoscopic examination of each ear, including visualization of the tympanum, is imperative for proper diagnosis and assessment of otitis externa. The initial treatment of this disease consists of irrigating and cleansing the external ear canal. Additional treatment consists of the use of ceruminolytic agents and, depending on the origin of the otitis, antibiotics (aqueous solutions) locally or parenterally, antifungal agents or parasiticides locally, and pH alteration. Bandaging the ears over the top of the animal’s head allows better ventilation of the ear canal.

Culture and sensitivity tests in cases of severe or repeated occurrences of acute otitis externa may obviate a future ear canal operation by identifying the bacterial etiologic agent and thus the antibiotic that should effectively eliminate that agent. Chronic otitis externa must be treated more vigorously. Instillation of “swimmer’s solution” (three parts 70% isopropyl alcohol and one part white vinegar) is useful for long-term treatment; it provides a cleaning-drying action and lowers the pH of the ear canal.

Surgical Treatment
(Lateral Ear Canal Resection)

Indications

When otitis externa becomes unresponsive to medical therapy, a lateral ear canal operation is indicated. Lateral ear canal resection is also indicated for frequent recurrence of otitis externa, for chronic otitis externa resulting from inadequate treatment or lack of treatment, for external ear canal thickening that does not concurrently obstruct the horizontal portion of the external ear canal, and for exposure and removal of small tumors or polyps.

The purpose of lateral ear canal resection is to provide environmental alteration by means of ventilation so moisture, humidity, and temperature are decreased. Lateral ear canal resection also provides drainage for exudates and moisture in the ear canal.

Surgical Technique

The patient is placed in lateral recumbency and is draped so the pinna and external ear canal region are left exposed and all anatomic relationships are identifiable (Figure 13-7). The veterinary surgeon initially is positioned ventral to the patient. A probe is inserted into the ventral ear canal to determine the canal’s depth. Two skin incisions are extended ventrally, parallel to each other, from the intertragic notch and the trago-helicene notch. These vertical incisions should be 1.5 times the length of the vertical ear canal. A transverse incision is made joining the vertical incisions ventrally (Figure 13-8). The skin is reflected to its dorsal attachment on the dorsal rim of the vertical ear canal. An incision is made through the subcutaneous tissue of the lateral surface of the cartilaginous vertical canal. With scissors, the subcutaneous tissue is reflected rostrally and caudally off the vertical ear canal (Figure 13-9). In similar fashion, the parotid salivary gland is reflected ventrally. The lateral aspect of the vertical ear canal should be exposed at this point.

The next portion of the surgical procedure is best performed from the dorsal aspect of the head. With scissors, two incisions are made in the cartilaginous vertical canal, one along the rostro- lateral aspect of the canal and one along its caudolateral aspect. For the incisions to be made properly, the pinna and the skin flap must be pulled dorsally and the vertical portion of the ear canal visualized. One blade of the scissors is placed into the vertical canal (Figure 13-10), which is then incised from the tragohelicene notch ventrally approximately half the length of the vertical ear canal. Both the rostral and caudal ear incisions should be alternately extended until the floor of the horizontal ear canal limits further advancement of the scissors. The lateral wall of the vertical ear canal is now reflected ventrally (Figure 13-11).
 

If the incisions have been made properly, the lateral wall will have a base of attachment equal to the width of the floor of the horizontal ear canal. Next, the skin flap and all but the proximal 2 cm of the lateral wall are removed. This section is used as the “drain board” flap.

The lateral flap is pulled ventrally. Size 3-0 nonabsorbable, preferably swaged-on suture material is used to suture the lateral ear canal flap and the remaining vertical ear canal to the adjacent skin in a simple interrupted pattern (Figure 13-12). The first suture is placed through the rostroventral edge of the epithelium and cartilage of the “drain board.” This suture is angled rostroventrally and is sutured to the skin. Similarly, the second suture is placed through the caudoventral edge of the flap and is sutured caudoventrally to the skin. The skin is adjusted before placement of this suture, so no redundant skin persists between these two sutures. The next two sutures should anchor the skin to the rostral and caudal walls of the opening of the horizontal ear canal. Additional interrupted sutures are placed to join the lateral ear canal flap to the skin and the edges of the vertical ear canal to the skin in cosmetic fashion.

The ear is placed approximately in its normal position, and the ear canal is checked for possible obstruction to drainage and ventilation by the anthelicene tubercle or proliferative ridges of tissue. If these tissues cause obstruction, they should be excised, and the resultant wound should be allowed to heal by second intention.

After all incisions have been closed, the pinna needs to be anchored over the head of the dog to provide ventilation and to prevent damage from head shaking. A porous bandage may be placed over the surgical site to protect it from scratching. Paw pads may be fashioned, or the patient’s legs may be hobbled as additional measures to protect the ear from self-trauma.
 

Postoperative Care

Postoperative care includes treatment with appropriate systemic antibiotics and management of self-trauma and ear movement. Coping with the prolonged healing time may be difficult. Healing time averages 10 to 14 days; if the suture line breaks down, healing may take longer. If lateral ear resection fails to control otitis externa, ear canal ablation needs to be considered. This procedure is discussed in the next section of this chapter.

Editor’s Note: To be effective, lateral ear canal resection must be performed early in animals with recurring otitis externa. If chronic tissue change such as skin hyperplasia/hypertrophy occurs as a result of chronic otitis, the efficacy of lateral ear canal resection is poor. Lateral ear canal resection should not be expected to cure otitis but rather acts as an adjunctive procedure improving ventilation and drainage to make ongoing medical therapy more effective.

Suggested Readings

Bojrab MJ, Dallman MJ. Lateral ear canal resection. In: Bojrab MJ, ed. Current techniques in small animal surgery. 2nd ed. Philadelphia: Lea & Febiger, 1983.

Coffey DJ. Observations on the surgical treatment of otitis externa in the dog. J Small Anim Pract 1970; 11:265.

Fraser G. Factors predisposing to canine internal otitis. Vet Rec 1961;73:55.

Fraser G, Withers AR, Spruell JSA. Otitis externa in the dog. J Small Anim Pract 1961;2:32.

Fraser G. et al. Canine ear disease. J Small Anim Pract 1970;10:725.

Grono LR. Studies of the microclimate of the external auditory canal in the dog. Parts I, II, and III. Res Vet Sci 1970;! 1:307.

Grono LR. Otitis externa. In: Kirk RW, ed. Current veterinary therapy. Vol. 7. Philadelphia: WB Saunders, 1980.

Ott RL. Ears. In: Archibald J, ed. Canine surgery. 2nd ed. Santa Barbara, CA: American Veterinary Publications, 1974.

Singleton WB. Aural resection in the dog. In: Jones BV, ed. Advances in small animal practices. Vol. 2. Oxford: Pergamon Press, 1960.

Zepp CP. Surgical correction of diseases of the ear in the dog and cat. Vet Rec 1949;61:643.

Gregory CR, Vasseur PB. Clinical results of lateral ear resection in dogs. J Am Vet Med Assoc 182: 1087, 1983.
 

An alternative surgical technique for chronic otitis externa has been used when the entire vertical canal is grossly distorted or filled with hyperplastic mucosa.

This technique combines the advantages of ablation (removal of the chronically infected vertical canal) with those of lateral ear canal resection (maintenance of drainage and hearing).

The preparation of the patient (Figure 13-13), skin incision, and vertical canal isolation are the same as described for lateral ear canal resection in the previous section of this chapter. Isolation of the vertical canal is continued medially until the entire canal is isolated (Figure 13-14). The auricular cartilage and skin are cut just dorsal to the opening of the vertical canal at the base of the pinna (Figure 13-15). This method allows complete mobilization of the vertical canal, which remains attached ventrally to the horizontal canal. The vertical canal is cut approximately 2 cm dorsal to the horizontal canal (Figure 13-16) and is discarded. The remaining vertical canal is incised both rostrally and caudally down to the horizontal canal (See Figure 13-16, inset), thus creating two rectangular flaps, a dorsal flap and a ventral flap (Figure 13-17). The ventral flap is sutured as described in the previous section of this chapter on treatment of otitis externa. The dorsal flap is sutured as depicted in Figure 13-17.

Aftercare consists of bandaging the patient’s ear over the head for 1 week and administering systemic antibiotics as determined by culture and sensitivity tests.
 

Introduction

Otitis externa is an insidious disease that is not usually debilitating, and the associated clinical signs are generally controlled until medical therapy is withdrawn. When multiple attempts at medical treatment fail, ear disease invariably progresses, and more extensive surgery is indicated to permanently relieve the clinical signs. Owners must understand that the frequency and severity of intra- and postoperative complications increase in proportion to the degree of surgery required. Thus, for the most part, early surgical intervention should be strongly advised when appropriate medical treatment for otitis externa fails or the condition becomes recurrent.¹ As the ear tissue damage becomes irreversible from chronic infection, drainage procedures fail and removal of the entire horizontal and vertical ear canal is required. This salvage procedure is known as total ear canal ablation (TECA).²

Secondary middle ear infection frequently develops in dogs with end-stage otitis externa.³ Consequently, variable results and high complication rates have been reported when TECA is preformed without a means of middle ear exposure and debridement (bulla osteotomy and curettage). Because TECA eliminates a primary pathway for exudate drainage, the external canal, recurrent deep infection occurs unless the middle ear is adequately evacuated. Inadequate removal of the secretory epithelium within the bulla or short osseous ear canal is responsible for such long-standing complications as persistent fistulation and abscessation.^1,4 For these reasons, most surgeons routinely combine lateral bulla osteotomy (LBO) through the same approach used for TECA. These combined procedures are described in this chapter.

Indications

TECA is most often performed for irreversible inflammatory ear canal disease in dogs. Other less common indications include severe ear canal trauma, neoplasia, and certain congenital malformations obstructing horizontal ear canal drainage. Irreversible inflammatory ear canal disease is present when one or a combination of the following is observed: hyperplasia of the epithelium occluding the horizontal ear canal, collapse or stenosis of the horizontal ear canal caused by infection within the cartilage or bone, or severely calcified periauricular tissue noted by palpation or observed on skull radiographs.

Many dogs that present to the veterinarian for surgical treatment of inflammatory ear disease have one or more irreversible conditions or indications for TECA. If medically unmanageable otitis externa is related to an ongoing generalized skin condition such as atopy or hypothyroidism, treatment of the primary dermatological disorder often helps control the ear disease. Concurrent skin disorders are very common in dogs with otitis externa. Almost 80% of dogs undergoing TECA in one report had one or more primary dermatological diseases including seborrhea, pyoderma, hypothyroidism, and atopy.⁵ When the related primary skin condition has been thoroughly diagnosed and appropriately treated but continues to be unresponsive, I prefer TECA for treatment of persistent otitis externa instead of surgical drainage procedures such as lateral ear canal resection. As the skin disorder progresses, so will the ear disease in most circumstances, and a lateral ear resection or vertical ear canal ablation will subsequently fail due to progressive inflammatory changes in the remaining canal. Similarly, if owners are incapable or unwilling to treat the skin or chronic ear disease appropriately, TECA may be indicated before irreversible changes exist.

Although TECA combined with LBO is indicated for a number of conditions in the dog, it is less commonly performed on cats. Irreversible, proliferative inflammatory changes resulting from long standing otitis externa do not appear to form as readily in cats as they do in dogs. Cats with otic tumors, such as ceruminous adenocarcinoma or basal cell carcinoma, diffuse polypoid disease, or those sustaining severe trauma to the ear canal are potential candidates for TECA.⁶ TECA is not usually required for cats affected with otitis media or inflammatory middle ear polyps, since the external ear canal is usually not severely affected, and exposure to the source of the clinical problem is best achieved with a ventral approach (ventral bulla osteotomy).

Owner Education

The owner must be made fully aware of the purpose of TECA as well as the possible sequelae before contemplating surgery. The surgeon should remind owners that the principle aim of TECA is to make their pet more comfortable by removing the source of pain and chronic infection. Elimination of further ear cleaning duties and the malodorous discharge are added benefits. Before surgery, however, owners seem to be concerned most about the appearance of their pet and whether their animal will be deaf after surgery. Generally, the appearance of floppy-eared dogs following TECA is unchanged. In erect-eared dogs, the extent of auricular and pinna cartilage removed determines whether the ear will stand following surgery. Removal of extensive proliferative tissue well up into the pinna will cause the erect ear to fall owing to lack of support at the ear base. The ear will remain somewhat erect if more than the proximal third of the vertical canal cartilage is preserved in dogs and cats. A simple modification of the TECA skin incision to create a single pedicle advancement flap has been found to maintain normal ear carriage in cats.⁷ The surgeon should not limit the amount of canal resection because of pressure from owners who want preservation of ear carriage at all costs. Continued irritation and pain can be expected if proliferative ear canal tissue remains following TECA.

Because TECA obliterates the external auditus, most owners are skeptical about their pet’s future hearing ability. Although the possibility of causing complete deafness remains, TECA combined with LBO should not be expected to affect hearing appreciably in most cases. Although air conducted sound may not be detected by brain evoked auditory testing after TECA, the ability to hear bone conducted sound is apparently preserved.^8,9 I warn owners that the quality of sound their dog can discern may change after surgery, but some hearing ability usually can be expected. Most complaints about hearing difficulty after TECA stem from inadequate owner evaluation or awareness of the pet’s hearing condition beforehand. The surgeon should try to make the owner aware of their dog’s hearing deficits before surgery to minimize this misunderstanding. Owners must be prepared for serious and potentially long-standing problems resulting from TECA. If nystagmus, circling, or loss of balance are present before surgery, exacerbation of these signs is common afterwards in the author’s experience. These signs usually improve if middle ear infection is eliminated but they may persist indefinitely. Transient, or more rarely, permanent facial nerve dysfunction may occur causing drooling from ipsilateral lip paralysis. Hemifacial spasm or facial nerve deficits that are present before surgery may indicate that the facial nerve is invaded by neoplasia or, more likely, that it is embedded in the horizontal canal or serious secondary middle ear infection is present. More dissection and retraction of the nerve may be required to free it up during TECA; this greatly increases the risk of iatrogenic facial nerve damage. Ocular problems from a diminished eye-blink response may be disastrous, particularly in exophthalmic dog breeds or those with inadequate tear production. Unresolved middle ear infection or any retained secretory tissue can cause recurrent abscessation and fistulation which may create conditions far worse for the owner and their pet than the presenting otitis externa problem.⁴ Proper preparation of owners for these potential problems by counseling before surgery is recommended.

Preoperative Considerations

A complete preoperative workup is essential to determine the extent and nature of the disease process and to predict possible surgical complications. Following routine physical examination, the external ear is inspected and palpated. A sharp pain response elicited during deep palpation of the ear canal usually indicates middle ear infection. Thickened and firm (calcified) ear canal tissue is a manifestation of irreversible inflammatory change. Evidence of a head tilt without other signs of inner ear disease (nystgmus, circling, loss of balance) usually indicates severe pain in the ear on the lower side. Neoplasia should be highly suspected if the ear drainage appears mostly as blood versus the more typical thick, foul-smelling exudate of an inflammatory otitis externa.

A complete neurologic examination should be performed to evaluate for facial nerve dysfunction (hemifacial spasm, poor palpebral reflex, lip droop) and inner ear involvement, especially in patients with chronic otitis externa. During preoperative workup, approximately 15% of patients with end-stage otitis are found to have partial or total facial nerve deficits.¹ It is important to identify patients with concurrent otitis media because they more often develop complications such as cellulitis, persistent fistulation, or abscessation following TECA.⁴ In addition, their postoperative care is more demanding and costly. Any hearing deficits or other neurologic problems should be clearly noted in the medical record and brought to the owner’s attention before TECA; otherwise, the owner may blame the surgeon if these deficits are noticed after surgery.

If the ear problem is a possible manifestation of a systemic skin disorder, a complete dermatologic examination should be performed and appropriate tests should also be completed. Postoperative head shaking and self-inflicted irritation to the remaining ear tissues may persist if the primary skin condition is neglected or inappropriately treated. This can be seen as a failure of the surgical procedure from the owner’s point of view.

The remaining preoperative workup is best performed while the patient is anesthetized. Thorough ear cleaning must be accomplished to allow maximal visualization of the canal during otoscopic examination. Otoscopic examination of both canals is indicated, even if one side superficially appears normal or if the condition of both ears is severely proliferative. Attention is directed at locating tumors or polyps, as these are not infrequent in older patients with long standing otitis externa. Otitis media is present if the tympanic membrane is not found and the tympanic bulla is filled with debris. Samples of suspicious tissues are submitted to help diagnose occult neoplasia, which may drastically change the prognosis as well as the owner’s wish to allow surgery on their pet. If neoplasia is suspected, local lymph nodes are examined and fine needle aspirates are evaluated cytologically for tumor staging. Chest radiographs are evaluated for evidence of metastatic disease or other occult thoracic problems. Rather than culturing the exudate at otoscopic examination, a more reliable result may be obtained if deep wound tissue and middle ear exudate are sampled at the time of surgery.

Skull radiographs help confirm the extent and severity of the ear canal pathology and may alert the clinician that otitis media or neoplasia is present. The ventrodorsal skull view may be used to help determine the horizontal canal patency and its diameter, and whether the canal walls have undergone irreversible change. Open mouth plain radiographic views of the bulla are best to evaluate for subtle middle ear change.¹⁰ Oblique lateral views may help demonstrate lytic neoplastic changes of the petrous temporal bone.

Radiography should not be regarded as a highly sensitive tool for the diagnosis of otitis media.¹¹ Positive radiographic signs such as thickening and calcification of the bulla indicate the presence of middle ear pathology, but false negative radiographs are common. The presence of predominately lytic changes in the rostroventral aspect of the bulla on oblique lateral views most often is a result of chronic inflammation in my experience. Conversely, evidence of bone lysis in other areas, particularly in the petrous temporal bone, suggests a neoplastic process. In summary, despite the lack of sensitivity, radiographic evaluation is recommended to evaluate for the presence of neoplastic invasion of bone, particularly when otoscopic examination of deep structures is not possible. Normal appearing skull radiographs do not rule out otitis media or neoplasia. CT imaging is a more sensitive modality to identify neoplastic and middle ear disease.

Surgical Anatomy

The surgeon must be aware of certain important structures before surgery (Figures 13-18 and 13-19). Branches of the great auricular and superficial temporal vessels should be avoided when incising through and dissecting medial to the vertical ear canal cartilage. The V-shaped parotid gland overlays the lateral and ventral areas of the ear canal, and it may be damaged if not retracted during horizontal ear canal exposure. Deep to the parotid gland are the facial nerve, internal maxillary vein, and branches of the external carotid artery. These structures are difficult to identify and preserve when dissecting deeply around the horizontal ear canal and tympanic bulla. The facial nerve emerges from the stylomastoid foramen, located just caudal to the ossesous portion of the ear canal, and travels rostroventrally directly under the horizontal ear canal. Additionally, the terminal branches of the facial nerve and auriculotemporal branch of the mandibular portion of the trigeminal nerve should be avoided rostral to the ear canal. Careful retraction of tissues and hemostasis, meticulous dissection, and staying close to the external ear canal cartilage and osseous bulla will reduce the risk of iatrogenic damage to many of the structures.
 

The external carotid artery and maxillary vein lie immediately ventral to the tympanic cavity and these must be safely retracted away from the tips of the ronguers during removal of the ventral aspect of the bulla (Figure 13-20). Sharp dissection and curettage of the rostral aspect of the osseous ear canal should be avoided to reduce the risk of retroarticular vein damage (Figure 13-21). During evacuation of debris and epithelium from the tympanic cavity, curettage should be avoided in the rostrodorsal and medial aspect of the bulla to preserve the ossicles and sensitive inner ear structures. The internal carotid artery can be damaged if the thin bone wall between the carotid canal and tympanic cavity has been eroded by chronic infection or neoplasia, or it may be disturbed by excessive medial pressure during curettage of the medial bulla wall (Figure 13-22).
 

Surgical Technique

Total Ear Canal Ablation

The ear canal is difficult to prepare aseptically, and contamination is inevitable during surgery. Therefore, a broad spectrum, bactericidal, intravenous antibiotic is given before and during surgery so that adequate blood levels are maintained in tissues during dissection. Alternatively, administration of antibiotics may be delayed until cultures of the osseous bulla are obtained during surgery. In either case, antibiotics are continued until the results of the intraoperative culture and susceptibility are available. The surgeon should use these susceptibility results to choose the appropriate drug for long-term therapy.

After anesthesia is induced, ample surrounding skin, the ear canal, and pinna are routinely prepared for aseptic surgery. The patient is placed in lateral recumbency with the head elevated by a towel to a level parallel with the chest wall. Figure 13-23 illustrates the TECA and LBO procedure. A T-shaped skin incision is made; the horizontal incision is parallel and just below the upper edge of the tragus between the tragohelicine and intertragic notch (Figure 13-23A). The vertical incision is created perpendicular from the midpoint of the horizontal incision to a point just ventral to the horizontal canal. The surgeon undermines and retracts the two resulting skin flaps, and exposes the lateral aspect of the vertical canal from the surrounding loose connective tissue (Figure13-23B). With curved Metzenbaum scissors, bluntly dissect around the proximal and medial portion of the vertical canal staying as close as possible to the cartilage.

Starting from the caudal aspect, cut through the medial vertical canal wall with serrated Mayo scissors and continue cutting rostrally until the ends of the original horizontal skin incision connect (Figure 14-23C). One must avoid inadvertent damage to the branches of the great auricular vessels that travel in a dorsal direction just deep to the medial canal wall. Damage to these branches can lead to a vascular necrosis of pinna skin, particularly in the area of the posterior incisure and cornu of the antitragus. Starting at the dorsal and rostral aspect, free the remaining vertical canal of tissue connections and continue to dissect dorsally close to the horizontal canal cartilage down to the rim of the boney external auditory meatus. (Figure 13-23D). Damage to the facial nerve and parotid gland is avoided by carefully retracting these structures away from the dissection plane at the ventral and caudal aspect of the horizontal canal. These aforementioned areas are approached last, so that soft tissues can be retracted sufficiently to allow maximal exposure during dissection. Occasionally, the facial nerve is entrapped and is hidden from view within extensively thickened and calcified horizontal canal tissue. In such cases, I first search for peripheral small facial nerve branches (internal auricular nerves) that perforate the cartilage on the caudal and more superficial aspect of the horizontal canal; these branches lead to the seventh nerve trunk. Alternately, one may palpate for a small sharp protuberance (ridge) which is the rim separating the caudal osseous ear canal from the stylomastoid foramen (origin of the facial nerve). Once this area is located, one follows the most proximal portion of the nerve as it courses directly lateral from the foramen. Entrapment is generally found as the nerve exits the foramen and begins its rostral course. Carefully dissect the remaining nerve from the canal. To avoid iatrogenic nerve trauma, one should always incise the horizontal canal attachment to the external auditory meatus away from the course of the facial nerve. Branches of the superficial temporal vessels originating from the retroarticular vein (retroarticular foramen) may be encountered during dissection of the rostral aspect of the canal from bone. Electrocoagulation or bone wax may be required to stop excessive hemorrhage. The entire canal should be removed and submitted for histologic examination. Rongeurs are usually required to excise remaining calcified attachments until the entire circumference of the external auditory meatus is seen as a white glistening edge.

In severely affected ears, a greenish-brown epithelial pouch (similar to the shape of a “sock”) is present within the external auditory meatus and tympanic cavity extending lateral and ventral to the tympanic bulla (Figure 13-23E). Removal of all secretory tissue is critical to the success of the surgery since chronic fistulization will occur if secretions form within this enclosed area. Grasp the dorsal aspect of the pouch and with traction, “tease out” the pouch in one piece if possible with a Freer elevator. A curette should be used to remove any remaining secretory tissue that is adherent to the walls of the boney meatus. This tissue is submitted for culture and susceptibility testing.
 

Lateral Subtotal Bulla Osteotomy¹

As the surgeon approaches the tympanic bulla, it is important to note that the bulla may be extensively remodeled (expanded) from a mounting cholesteatoma or chronic bulla osteitis. Important neurovascular structures may be more tightly draped around an expanded bulla. This close anatomic relationship greatly increases the risk of iatrogenic damage if the following steps are not carefully completed. The location of the facial nerve is important and retractors should be placed laterally (or more superficially) to spare the nerve (Figure 13-24). The author believes overzealous retraction during attempts at exposing deep structures during LBO is a major cause of temporary postoperative facial nerve dysfunction. Bluntly dissect soft tissue directly from the lateral and ventral aspects of the tympanic bulla with a Freer periosteal elevator. Stray dissection away from the bulla is avoided particularly rostral to the external auditory meatus (EAM) to spare the retroarticular vein and ventral to the bulla (to avoid the carotid artery, maxillary vein, and their branches). Soft tissue is elevated and retracted from the ventral aspect of the bulla using Freer elevators. During the entire LBO procedure, the surgeon is careful to visualize what is caught in the jaws of the ronguers to help avoid inadvertent damage to important surrounding soft tissue. Bone removal is begun with Cleveland or Lempert rongeurs; this choice depends on the thickness of bone and size of the patient. Controlled bites of bone are taken from the floor of the EAM. This will create a notch in the soft tissue lining and ventral bony floor of the EAM. (Figures 13-25 and 13-26). The remaining soft tissue is peeled from the osseous ear canal by starting blunt dissection with Freer elevators at the cut edge of epithelium just adjacent to the notch. Once this dissection is complete, the EAM will appear as a shiny white surface throughout its circumference. The osseous ear canal is usually the thickest part of the tympanic bulla removed during LBO. The surgeon continues bone removal from the ventral osseous ear canal and into the ventral tympanic cavity with bone rongeurs. Samples of tissue and debris are collected and submitted for biopsy and culture/susceptibility. The facial nerve trunk is gently elevated from the caudal (vertically oriented) shelf of bone between the stylomastoid foramen and the EAM. Next, this vertical sharp bony ridge is carefully removed with Lempert ronguers (Figure 13-27). This will allow gentle elevation of the facial nerve from the lateral face of the caudolateral tympanic bulla. Keeping the nerve safely retracted with the Freer elevator, one should try to angle Cleveland or Lempert rongeurs into the EAM and remove the bone on the lateral aspect of the caudal tympanic bulla. If this is not possible, I prefer Kerrison rongeurs to begin bone removal ventral to the stylomastoid foramen just caudal to the EAM (Figure 13-28). Bone is very brittle and hard in this area, but once the shelf and bone just caudal to the EAM have been removed, the remaining caudolateral bulla bone is usually thinner and easier to excise, and Lempert rongeurs will suffice for bone removal. One should not attempt to rongeur bone rostrally since structures of the epitympanic recess could be damaged and the retroarticular vein may be torn. The retroarticular vein cannot be exposed readily and usually is not evident to the surgeon unless it is damaged. If brisk hemorrhage is encountered in the rostral aspect of the EAM, a cotton tipped swab should be used to hold direct pressure on the origin of the bleeding area. It should be noted that the retroarticular foramen opens ventrally, not laterally, just rostral to the EAM, so bone wax must be pushed in a dorsomedial direction to fill the foramen and maintain hemostasis. The LBO is completed once most of the lateral and ventral aspects of the tympanic bulla have been removed. This will create a large window to adequately view the tympanic cavity interior (Figure 13-23F).
 

The interior aspect of the tympanic cavity is carefully inspected after irrigating the area with tepid sterile saline solution. When normal, the bulla is lined with a thin transparent epithelium, which does not need to be disturbed. If the external ear disease is chronic and there are signs of bulla osteitis, the tympanic cavity is usually (either partially or completely) lined with a greenish-brown to dark brown hyperplastic epithelial tissue. In most cases, a small cavity is found just within the rostral tympanic cavity (adjacent to the opening of the auditory tube), in which a “sock” of epithelium (sometimes coined “false middle ear or acquired cholesteatoma”) is found.^14,15 In either case, all abnormal epithelium inside the tympanic cavity should be removed (Figure 3-23E). The sock of epithelium is generally easy to remove; the edge of the epithelium is grasped with hemostats, and while placing traction on the tissue, Freer elevators or Daubenspeck curettes are used to separate the attachments and remove the entire undisturbed epithelial cuff. If discolored or abnormal soft tissue clings from the dorsal compartment, it is carefully teased off with fine tipped curved hemostats. The ossicles are usually found tucked in the dorsal epitympanic recess just medial to the bony dorsal rim of the EAM. There is no need to remove the ossicles unless abnormal soft tissue or the tympanum is adhered to them. Curettage is avoided around the thin promontory areas, located dorsomedially that houses the sensitive inner ear structures (Figure 13-29). Excessive downward (medial) force with the curette on the medial surface of the tympanic cavity should be avoided since bone covering the carotid canal (housing the internal carotid artery) can be penetrated causing profuse hemorrhage. If this occurs, the tympanic cavity is tightly packed with gauze stripping, and one should wait at least 5 minutes until hemostasis is established, and then the packing should be removed slowly to continue the inspection. Daubenspeck or malleable curettes are used to scrape the rostral, ventral and caudal tympanic cavity. Abnormal tissues are submitted for histologic evaluation. The epitympanic recess and the EAM should be carefully inspected for remnants of abnormal epithelium or retained tympanum. The entire tympanic cavity should be irrigated and inspected again and any remaining suspicious tissue and bony fragments are removed. Thorough irrigation of the entire wound, especially the dead space just medial to the base of the pinna is performed with sterile saline.
 

Ideally, an active suction drain system (Jackson-Pratt) is recommended in those patients with heavy contamination intra-operatively, uncontrolled bleeding, concurrent para-aural abscessation, or when the bulla is difficult to clean out properly. Alternately, if a closed suction system is not available, a passive surgical drain (Penrose drain) may be used. If the tissue surrounding the wound has minimal contamination, inflammation or hemorrhage, and the tympanic cavity is thoroughly evacuated, there is usually no need for wound drainage.¹⁶ Dead space is closed in the subcutaneous tissue with 4-0 monofilament absorbable material. The skin is closed routinely with simple interrupted 4-0 monofilament nonabsorbable material to complete the total ear canal ablation.

Postoperative Care

If a drain is used, a loose, padded head bandage is placed to cover the drain and surgical site until the drain is removed, usually within 48 to 72 hours. Significant pharyngeal swelling can result particularly if TECA and bulla osteotomy are performed bilaterally. In addition, bandages may further reduce pharyngeal airway size and this can cause suffocation in the early postoperative period. These patients should be closely monitored for signs of dyspnea especially during the first 24 hours. An Elizabethan collar is used when needed to reduce self-trauma until sutures are removed in 10 to 14 days. During bandage changing, wounds are examined for evidence of fluid accumulation or ensuing infection. If signs of acute postoperative infection occur, sutures in the vertical portion of the wound are removed and the wound is opened fully to allow adequate drainage. Systemic antibiotics, based on the intraoperative culture and susceptibility results, are administered for a minimum of three weeks. Postoperative treatment for any underlying systemic skin disorder is continued.

Patients undergoing TECA and LBO often show evidence of extreme postoperative pain due to inflammation and nerve stimulation from deep wound dissection and bone removal. The surgeon must be prepared to aggressively manage this pain both preemptively and postoperatively. General postoperative guidelines for management of small animals after TECA and LBO are beyond the scope of this chapter, and are discussed elsewhere. (See Chapter 9) I prefer to give injectable opioid medications and NSAIDS in advance of surgery to reduce the amount of postoperative analgesics required to maintain patient comfort. A fentanyl patch can be applied 24 hours before surgery as another preemptive analgesic option. Postoperatively, injectable opioid analgesics combined with local anesthetic patches or constant local anesthetic infusion are also good options. The patient is released from the hospital and NSAID treatment is continued for 3 to 5 days if indicated.

Complications and Treatment

Many complications have been reported after TECA.^17-21 Most complications related to the surgery (wound infections and seromas) are short-lived and resolve within two weeks if treated appropriately. Extensive bacterial numbers are present in occluded chronically infected ear canals even after proper aseptic preparation of the area. Acute postoperative wound infection is not uncommon after TECA since wound contamination is inevitable. Proper intraoperative wound irrigation, antibiotic administration, and drainage help reduce this problem. Evidence of avascular skin slough at the proximal caudal skin margin and acute cellulitis are managed with open wound management and debridement until the area heals completely. Animals afflicted with inner ear signs before surgery may deteriorate immediately after anesthetic recovery and these signs may persist indefinitely in my experience. Until proven otherwise, inner ear signs that first develop in a patient a week or more after surgery are attributable to a fulminant abscess within the middle ear. Surgically induced Horner’s syndrome tends to occur from middle ear curettage during TECA only in the cat. This will usually resolve within several weeks provided middle ear infection has been eradicated.

Many dogs experience slow or incomplete eye blink response and ear or lip droop immediately after surgery owing to paresis of muscles innervated by the facial nerve. Artificial tears or ointments are used prophylactically until the affected eyes regain full function, usually within five days after surgery. If no evidence of eye blink is appreciable by four weeks following surgery, permanent damage can be expected. Overall, about 10% to 15% of dogs have permanent facial nerve damage following TECA.¹⁷ This does not cause significant disability in my experience, provided normal tear flow is present and the eye is not predisposed to exposure keratitis from exophthalmia. In summary, most facial nerve damage is iatrogenic and transient and is most often caused by overzealous retraction during ear canal dissection in my experience. Dissection of an entrapped facial nerve or en bloc resection of neoplasia may cause permanent damage.

Fistulization or skin sinus formation and middle ear infection are considered the most serious complications from TECA since these problems can cause clinical disability worse than the original chronic ear disease. Long-term antibiotic treatment and wound drainage rarely eliminate the problem in my experience. Persistent infection usually requires wound exploration for successful treatment, a costly and difficult procedure.⁴ Persistent wound drainage or fistulization forms anytime from one month to over two years after surgery in about 5% to 10% of patients undergoing TECA and LBO for chronic otitis.⁴ Persistent infection is most commonly attributed to a remnant of secretory tissue within the external auditory meatus or tympanic cavity. Isolation and removal of retained secretory epithelium with proper drainage of exudates permanently eliminates the problem. Ventral or LBO may be required depending on the suspected source of the persistent infection.^4,22 CT imaging is useful in helping the surgeon decide which approach is best. I, and others, prefer to use the lateral approach through the original incision site if retained horizontal ear canal tissue is the cause of the fistulization.²² Ventral bulla osteotomy is the preferred route for exploration if the nidus is believed to be located in the middle ear because it avoids dissection through the previous surgery site and allows maximal exposure of the tympanic cavity. Approximately 70%-85% of patients explored for persistent infection will be cured.^4,22 Despite the expense and potential for serious complications following TECA, most owners are satisfied with the procedure and improvement in their dog’s demeanor.

References

1. Smeak DD, Kerpsack S: Total ear canal ablation and lateral bulla osteotomy for management of end-stage otitis externa. Seminars in Veterinary Medicine 8:30-41, 1993.

2. Smeak DD: Total ear canal ablation and lateral bulla osteotomy. In Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Williams and Wilkens, Baltimore, 1998, pp 102-9.

3. Cole LK, Kwocka KW, Kowalski JJ, Hillier A: Microbial flora and antimicrobial susceptibility patterns of isolated pathogens from the horizontal ear canal and middle ear in dogs with otitis media. J Am Vet Med Assoc 15:212:534-8, 1998.

4. Smeak DD, Crocker CB, Birchard SJ: Treatment of recurrent otitis media after total ear canal ablation and lateral bulla osteotomy in dogs: nine cases (1986-1994). J Am Vet Med Assoc 209:937-942, 1996.

5. Mason, LK, Harvey CE, Orsher, RJ: Total ear canal ablation combined with lateral bulla osteotomy for end-stage otitis in dogs-results in thirty dogs. Vet Surg 17:263-268, 1988.

6. Bacon NJ, Gilbert, RL, Bostock DE, et al.: Total ear ablation in the cat: indications, morbidity, and long-term survival. J Small Anim Pract 44:430-4, 2003.

7. McNabb AH, Flanders, JA: Cosmetic results of a ventrally based advancement flap for closure of total ear canal ablation in 6 cats: 2002-2003. Vet Srug 33:435-9, 2004.

8. Krahwinkel DJ, Pardo AD, Sims MH, Bubb WJ: Effects of total ablation of the external acoustic meatus and bulla osteotomy on auditory function in dogs. J Am Vet Med Assoc 202:949-52, 1993.

9. McAnulty JF, Hattel A, Harvey CE: Wound healing and brain stem audtory evoked potentials after experimental total ear canal ablation with lateral tympanic bulla osteotomy in dogs. Vet Surg 24:1-8, 1995.

10. Geary CJ: Radiographic aspects of otitis media. Auburn Vet 21: 71-3, 1965.

11. Remedios AM, Fowler JD, Pharr JW: A comparison of radiographic versus surgical diagnosis of otitis media. J Am Anim Hosp Assoc 27:183-8, 1991.

12. Garosi LS, Dennis R, Schwarz T: Review of diagnostic imaging of ear diseases in the dog and cat. Vet Radiol Ultrasound 44: 137-46. 2003.

13. Smeak DD, Inpanbutr: Lateral approach to subtotal bulla osteotomy in dogs: pertinent anatomy and procedural details. Compend Contin Educ Pract Vet 27:377-385, 2005.

14. Lesinskas, E, Lesinskas R, Vainutiene V: Middle ear cholesteatoma: present-day concepts of etiology and pathogenesis. Medicina (Kaunas) 38: 1066-71, 2002.

15. Davidson EB, Brodie Ha, Breznoch EM: Removal of a Cholesteatoma in a Dog, Using a Caudal Auricular Approach. J Am Vet Med Assoc 211:1549-1553, 1997.

16. Devitt CM, Seim HB, Willer R, McPherro M, Neel, M: Passive drainage versus primary closure after total ear canal ablation-lateral bulla osteotomy in dogs: 59 dogs (1985-1995) Vet Surg 26:210-216, 1997.

17. Smeak DD, Dehoff WD: Total ear canal ablation-clinical results in the dog and cat. Vet Surg 16:161-170.

18. Mason LK, Harvey CE, Orsher RJ: Total ear canal ablation combined with lateral bulla osteotomy for end-stage otitis in dogs-results from thirty dogs. Vet Surg 17: 263-268, 1988.

19. Matthieson DT, Scavelli T: Total ear canal ablation and laeral bulla osteotomy in 38 dogs. J Am Anim Hosp Assoc 26:257-267, 1990.

20. Beckman, SL, Henry WB, Cechner P: Toal ear canal ablation combining osteotmy and curettage in dogs with chronic otitits externa and media. J Am Vet Med Assoc 196:84-90, 1990.

21. Sharp NJH: Chronic otitis externa and otitis media treated by total ear ablation and ventral bulla osteotomy in thirteen dogs. Vet Surg 19:162-166. 1990.

22. Holt D, Brockman, DJ, Sylvestre AM, Sadanaga KK: Lateral exploration of fistuals developing after total ear ablation: 10 cases (1989- 1993). J Am Anim Hosp Assoc 32:527-30. 1996.
 

Indications

Ventral bulla osteotomy is indicated in dogs to treat chronic otitis media that has not responded to appropriate medical therapy, benign neoplasia affecting the middle ear, and cholesteatomas. In dogs with chronic otitis media, the surgeon must carefully evaluate the condition of the external ear canal before performing a ventral bulla osteotomy. Dogs with marked otitis externa causing narrowing or stenosis of the external ear canal usually require total ear canal ablation. In these cases, a concurrent lateral rather than ventral bulla osteotomy is performed. Ventral bulla osteotomy has been used to successfully treat recurrent or ongoing otitis media in dogs after total ear canal ablation and lateral bulla osteotomy. In addition, the surgical approach used to expose the ventral aspect of the bulla is very useful when exploring for foreign bodies that have pentrated the caudal pharynx or for evaluating neoplasia that may occur in this area of the head and neck.

Refractory otitis media requiring surgical drainage is less common in cats than in dogs. In cats, the most frequent indication for ventral bulla osteotomy is exploration to remove the middle ear component of aural or nasopharyngeal polyps. Rarely, the ventral approach has also been used in cats to treat benign and malignant masses involving the middle ear.

Bulla Anatomy

The tympanic bulla in dogs is part of the petrous temporal bone and forms a pear-shaped cavity. The larger main portion of the bulla extends ventrally. The smaller epitympanic recess extends dorsally and contains the auditory ossicles, the malleus, incus and stapes, which extend from the tympanic membrane to the vestibular window (Figure 13-30). Medial to the epitympanic recess is a bony eminence, the promontory, which contains the cochlea. The cochlear window is located on the caudolateral aspect of the promontory (Figure 13-31). Curettage of the epitympanic recess and in the area of the promontory should be avoided to prevent iatrogenic damage to the vestibular and cochlear windows. Damage to these structures may cause postoperative otitis interna and balance/equilibrium problems for the dog.

In the cat, the middle ear is divided by an incomplete boney septum into a large ventromedial compartment and a smaller dorsolateral compartment. During ventral bulla osteotomy in cats, the larger ventromedial compartment is invariably entered first. The septum runs obliquely from craniomedial to caudolateral in the rostral one-third of the bulla. Removing this septum and opening the dorsolateral compartment is mandatory during bulla osteotomy for polyps as this compartment contains the opening of the Eustachian (auditory) tube. Once the septum is removed, the complete extent of the oval promontory can be visualized (Figure 13-32). The cochlear window is located in the caudolateral aspect of the promontory. Postganglionic sympathetic nerve fibers from the cranial cervical ganglion enter the bulla caudally and fan out over the promontory where they may be damaged by curettage.

Surgical Technique

The ventral approach to the bulla is similar in cats and dogs. The animal is positioned in dorsal recumbency with a folded towel placed under the neck and tape is used to secure the rostral mandibles to the surgery table. Each bulla lies medial and slightly caudal to the vertical ramus of the mandible in a paramedian position. The bulla is palpable percutaneously in most cats but rarely in dogs. It is helpful to identify the mandibular salivary gland located at the bifurcation of the jugular vein by palpation immediately before surgery. A longitudinal paramedian skin incision is made between the larynx medially and vertical ramus of the mandible laterally, starting just rostral to the larynx and extending 1-5 cm caudal to it, depending on the size of the animal. The platysma muscle is incised longitudinally and the mandibular salivary gland identified. Dissection continues medial to the salivary gland, which must be carefully separated from the linguo-facial branch of the jugular vein (Figure 13-33). A small venous branch draining from the salivary gland into the linguofacial vein may require ligation and division. The separation between the large digastricus muscle laterally and the myelohyoideus muscle medially is identified. Correct location of this dissection plane is crucial for this approach. If this plane is correctly identified and dissected, the hypoglossal nerve will be visible coursing cranially on the medial aspect of the surgical field. The hypoglossal nerve is gently retracted and protected from injury throughout the procedure. Surgical exposure is maintained by careful placement of hand-held or Gelpi tissue retractors.
 

At this point, it is important to accurately identify the bulla by palpation. In cats, the large ventral dome of the bulla is easily palpable. In dogs, especially those with chronic otitis media, the bulla is not as apparent on palpation, feeling more flat than domed. To further localize the bulla, the surgeon should gently palpate for the stylohyoid bone coursing dorsally and laterally from the remainder of the hyoid apparatus. The hyoid apparatus in both species is attached to the caudal and lateral aspect of the bulla by the tympanohyoid cartilage, a small extension of the stylohyoid bone. In dogs, the paracondylar process of the occipital bone can often be palpated as a pointed structure protruding ventrally from the skull just caudal to the bulla. As an additional means to confirm the bulla’s location, a non-sterile assistant can place an index finger into the mouth and palpate the hamular processes of the pterygoid bones. The assistant moves a finger to the bulla, which lies just caudal and lateral to this process on either side of the skull. The surgeon palpates the assistant’s finger to confirm the location of the bulla.

Once the bulla is accurately identified, dissection proceeds dorsally. The bulla lies in a “V” formed by the internal and external branches of the carotid artery. These branches should be identified and carefully dissected or protected in the dog. In dogs, the thin muscular tissue lying immediately ventral to the bulla is bluntly separated parallel with the orientation of its fibers. In cats, the loose areolar tissue covering the bulla is bluntly elevated or dissected. The periosteum of the bulla is incised and elevated from the entire ventral surface of the bulla. The surgeon should take the time to ensure adequate lateral dissection and exposure of the bulla in cats before opening the bulla to facilitate exposure of the dorsolateral bulla compartment. A sharp Steinman pin in a Jacob’s chuck is used to make the initial opening into the bulla. Very little dorsal pressure is applied to the chuck to prevent the pin from lurching into the dorsal aspect of the bulla when it enters the tympanic cavity. In dogs with chronic otitis media and cats with long-standing polyps, the wall of the bulla can be quite thick and patience is required whle drilling with the Steinman pin. Alternatively, some surgeons prefer a powered drill for entrance to the bulla. Once an initial bulla opening has been made, it is enlarged with rongeurs.
 

In cats, the larger ventromedial compartment is opened first. The septum separating this compartment from the dorsolateral compartment is on the craniolateral aspect of the medial compartment. In some cats, the septum can be opened with a small, fine-tipped, single-action rongeur. In other cats, the septum must be penetrated by a Steinmen pin and the opening enlarged with rongeurs. With the bulla fully opened, the promontory is visible in both species as an oval shaped bony protuberance in the dorsal aspect of the bulla. Curettage over the promontory, particularly the caudal aspect, and in the epitympanic recess is avoided to prevent damage to the cochlear (round) and vestibular (oval) windows. Diseased or infected tissue is removed and samples are taken for biopsy and culture and sensitivity testing. The bulla cavity is thoroughly flushed with warm, balanced electrolyte solution and suctioned dry. Often, flushing and suctioning will identify residual tags of epithelial lining that are then removed. A latex drain is loosely placed into the bulla cavity without anchoring sutures. It exits through a separate small skin incision. The deeper layers of the surgical field are closed with a few single interrupted sutures of monofilament absorbable suture, taking care to avoid the hypoglossal nerve. The subcutaneous tissue and skin are closed in a routine manner. The latex drain is anchored to the skin with two single interrupted sutures.

Postoperative Care

Recovery from anesthesia is routine in most animals. The nasopharynx is inspected and suctioned while the animal is still under anesthesia as blood or flush solution can travel from the middle ear to the nasopharynx by the Eustachian tube and be aspirated after extubation if it is not removed. Cats with polyps in both middle ears that have undergone bilateral bulla surgery must be carefully observed during anesthetic recovery. Swelling in the nasopharynx postoperatively can cause respiratory compromise. This can be alleviated by gently opening the cat’s mouth to encourage mouth, rather than nasal breathing until the cat is fully recovered from anesthesia. Drains are usually removed 24-48 hours postoperatively.

Complications

Complications following ventral bulla osteotomy in dogs are uncommon but are usually associated with damage to structures of the inner ear. Clinical signs include nystagmus, head tilt, and circling. Neurologic signs are more common after ventral bulla osteotomy in cats with an 80% incidence of postoperative Horner’s syndrome due to damage to the sympathetic nerve fibers in the middle ear. The clinical signs of Horner’s syndrome, miosis, ptosis, and prolapse of the third eyelid resolve within 4 to six weeks in the majority of cats. Approximately 40% of cats may have clinical signs of otitis interna after ventral bulla osteotomy for polyp removal. These clinical signs are generally transient.

References

Fraser, G., Gregor, W.W., Mackenzie, C.P., et al. Canine ear disease.J Small anima Pract 1970; 10:725-754.

Getty, R. The ear. In: Evans H.E., Christensen, G.C., ed.: Miller’s Anatomy of the Dog. Philadelphia: WB Saunders, 1979, pp 1062-1069.

Harvey, C.E.: Diseases of the middle ear. In Slatter, D.H., ed.: Textbook of Samll Animal Surgery, ed. 1. Philadelphia: WB Saunders, 1985, pp 1919-1923.

Kapatkin, A.S., Mathiesen, D.T., Noone, K.E. et al. Results of surgery and long-term follow-up in 31 cats with nasophyngeal polyps. J Am Anim Hosp Assoc 1990; 26:387-392.

Little, C.J.L., Lange J.G. The surgical anatomy of the feline bulla tympanic. J Small Anim Pract 1986; 27:371-378.

Little, C.J.L; Lane, J.G.; Pearson, G.R. Inflammatory middle ear disease of the dog: The clinical and pathological features of cholestetoma, a complication of otitis media. Veterinary Record. 199. 128:14, 319-322.

Lucroy, M.D., Vernau, K.M., Samii, V.F. et al. Middle ear tumours with brainstem extension treated by ventral bulla osteotomy and craniectomy in two cats. Vet Comp Oncol 2004; 2:234-242.

Smeak, D.D., Crocker, C.B., Birchard, S.J. Treatment of recurrent otitis media that developed after total ear canal ablation and lateral bulla osteotomy in dogs: Nine cases (1986-1994). J Am Vet Med Assoc 1996. 209:5, 937-942.