Introduction
Brachycephalic dogs frequently present with signs of upper airway obstruction as a result of an anatomical distortion of their faces caused by an exaggerated and incorrect breed selection.1 Their head shape is the result of an inherited developmental defect of the bones of the base of the skull, which grow to a normal width, but reduced length without proportionate reduction of the soft tissues of the head. The subsequent increased airway resistance in their hypoplastic airways leads to dyspnea, heat, and exercise intolerance, and secondary gastrointestinal abnormalities, which all leads to a significantly increased risk for any anaesthetic event and subsequent recovery. In addition, the occipital and temporal bones are more compressed as well, which has led to hypoplasia of the tympanic bullae and abnormal function of the Eustachian tube. The horizontal ear canals of these breeds are known to be very narrow and chronic otitis externa is commonly encountered and can rapidly result in complete obliteration of the lumen of the canals with hyperplastic tissue. Ear surgery is challenging, even in dolichocephalic dog breeds, but can be very complicated in brachycephalic breeds because of these factors mentioned. Indications for total ear canal ablation and lateral bulla osteotomy (TECA/LBO) in brachycephalics are usually proliferative otitis externa, chronic otitis media, or ear canal neoplasia.2,3 After a proper diagnostic workup it can be decided either to treat the patient with topical and/or systemic medications or to proceed with surgery. The owners should be properly informed prior to surgery about the benefit of surgery, the costs, the alternatives and the risks and complications of both the surgery itself as well as the anaesthesia.
Anaesthesia and Perioperative Medication
The choice of anaesthesia depends on several factors such as the patient's age, personality, general health and condition, and underlying diseases.2 General anaesthesia with endotracheal intubation is indicated in all cases of invasive ear surgery in brachycephalic dogs. Systemic, broad-spectrum antibiotics are used intravenously preoperatively with all otologic surgeries, for strict asepsis is impossible to achieve in the ear canal. Ideally, the choice of antibiotic should be determined by bacterial culture and susceptibility testing, but amoxicillin with clavulanic acid can be used as a first-choice antibiotic for all procedures.2 Postoperatively, oral antibiotics are prescribed for 10 days after uncomplicated total ear canal ablation and for 14–28 days in case of middle ear infections, regurgitation during or after the anaesthetic, and/or aspiration pneumonia. In most cases, it is advisable to provide analgesia with both opioid analgesics and nonsteroidal anti-inflammatory drugs, for at least the first 72 hours after surgery. An additional 3–7 days of NSAIDs can be prescribed after total ear canal ablation or bulla osteotomy.
Position of the Patient and Surgeon
The patient is placed in lateral recumbency on the contralateral side of the ear problem.2,4,5 The patient's head and neck are slightly elevated from the table with inflatable mattresses to reduce interference of the surgeon's arms and hands with the shoulder region and front legs of the patient. The front legs are either completely stretched forwards under the head or backwards under the thoracic cavity, to allow the surgeon maximal access to the ear when positioned on the ventral side of the patient. The patient's head is additionally rotated ventrally for 30 degrees to allow for better vision of, and access to the horizontal ear canal.
Preparation of the Operative Site
The operative site is prepared by shaving the patient's hair away from all areas of the auricle that have to be manipulated during surgery including the actual site of incision. The operative area is then sterilized routinely. The use of antiseptics and disinfectants should be limited, however, to the area outside the outer ear canal to prevent leakage of these ototoxic chemicals into the ear canal and possibly the middle ear cavity.2,3 Placing a temporary gauze inside the ear canal while preparing the operative site and covering this area with gauzes moistened with disinfectant after initial preparation, rather than spraying it on the surgical area are two useful measures that will help in preventing ototoxicity.
Instruments
With the abundance of high-quality surgical instruments on the veterinary market nowadays from many manufacturers, an instrument for virtually every application is available. The economics of the veterinary practice is usually the limiting factor though, making selection of the proper instruments a necessity. In addition to a basic surgical set, the following instruments are highly recommended: Mayo-Noble dissecting scissors, delicate curved Kelly or Toennis-Adson dissecting scissors, Williger raspatories, Kerrison rongeurs, Böhler and/or Zaufal-Jansen bone rongeurs, Wigro curette, and Frazier and Adson Suction cannulae.2
Total Ear Canal Ablation
A V-shaped incision is made in the skin from the intertragic incisure to the ventral limit of the vertical ear canal and from the tragohelicine incisure to the same ventral point.2,3 The skin flap is retracted dorsally and the lateral aspect of the vertical ear canal is exposed. The cartilage and the skin of the medial wall of the ear canal are separated from the cartilage and the skin on the inner side of the base of the pinna by use of strong scissors. The vertical ear canal is now dissected to the level of the horizontal ear canal. Appropriate care should be taken to avoid the facial nerve in this area. The dissection is continued with freeing the horizontal part of the ear canal from the surrounding tissues to the level of the external acoustic meatus. The cartilaginous part is separated from the osseous part with scissors and removal of all of the skin lining the osseous external ear canal is accomplished with a small curette. The procedure is completed when after removal of the tympanic membrane, no secretory tissue is left and only bone is visible. When this is performed correctly, no lateral bulla osteotomy is necessary in absence of chronic otitis media. With chronic otitis media and accumulation of inflammatory tissue or thick exudate in the middle ear cavity, a lateral bulla osteotomy is performed from this point on. After completion of the TECA or TECA with LBO, the pinna is remodeled and sutured with absorbable suture material.2,3 A Penrose drain is placed and subcutaneous tissue and skin under the pinna are closed in a routine matter. Complications after TECA are facial nerve paralysis, wound infection and dehiscence and chronic fistulation, but most complications can be avoided with meticulous surgical technique.6,7 Cholesteatoma formation has been reported as a late complication of TECA/LBO in two brachycephalic dogs.8
Lateral Bulla Osteotomy
After total ear canal ablation, the tissues from the lateral aspect of the bulla are bluntly dissected as close to the bone as possible avoiding damage to the facial nerve and branches of the external carotid artery that travel just ventral to the bulla with small periosteal elevators or raspatories.2,4 The lateral and ventral aspect of the bulla can now be removed with Kerrison, Böhler and/or Zaufal-Jansen rongeurs until adequate visualization of the middle ear cavity is possible. Samples can be obtained for culture and susceptibility testing and for cytology or histopathology. A bone curette is used to gently remove any remaining epithelium or debris from within the bulla, taking care to preserve the auditory ossicles and cochlea on the dorsomedial side of the bulla. After curettage, the tympanic cavity is copiously lavaged with warm saline and closure is as for total ear canal ablation.
References
1. Oechtering GU. Brachycephalic syndrome - new information on an old congenital disease. Veterinary Focus. 2010;20(2):2–9.
2. Haar ter G. Basic principles of surgery of the external ear (pinna and ear canal). In: Kirpensteijn J, Klein WR, eds. The Cutting Edge: Basic Operating Skills for the Veterinary Surgeon. London, UK: Roman House Publishers; 2006: 272–283.
3. Venker-van Haagen AJ. The ear. In: Venker-van Haagen AJ, ed. Ear, Nose, Throat, and Tracheobronchial Diseases in Dogs and Cats. Hannover, Germany: Schlütersche Verlagsgesellschaft mBH & Co.; 2005: 1–50.
4. White RAS. Middle and inner ear. In: Tobias KM, Johnston SA, eds. Veterinary Surgery Small Animal. St. Louis, MO, USA: Elsevier Saunders; 2012: 2078–2090.
5. Bacon NJ. Pinna and external ear canal. In: Tobias KM, Johnston SA, eds. Veterinary Surgery Small Animal. St. Louis, MO, USA: Elsevier Saunders; 2012: 2059–2077.
6. Beckman SL, Henry WB, Cechner P. Total ear canal ablation combining bulla osteotomy and curettage in dogs with chronic otitis externa and media. Journal of the American Veterinary Medical Association. 1990;196(1):84–90.
7. Matthieson DT, Scavelli T. Total ear canal ablation and lateral bulla osteotomy in 38 dogs. Journal of the American Animal Hospital Association. 1990;26:257–267.
8. Schuenemann RM, Oechtering G. Cholesteatoma after lateral bulla osteotomy in two brachycephalic dogs. Journal of the American Animal Hospital Association. 2012;48:261–268.