Introduction

Ear surgery in cats is most commonly performed to treat the consequences of chronic viral otitis media with polyp formation in the middle ear, extending through the tympanic membrane into the ear canal or through the Eustachian tube into the nasopharynx.^1,2 Otitis media, polyp formation and treatment of this with simple traction avulsion via a lateral approach to the ear canal or ventral bulla osteotomy will be discussed in this lecture. In addition, surgery of the auricle for chronic inflammation or neoplastic disease is performed regularly and the technique of pinnectomy to treat these conditions will be discussed as well.³

Peri- and Polychondritis of the Auricle

Relapsing polychondritis is an autoimmune disease recognized in cats with recurrent episodes of inflammation of the auricular cartilage.⁴ Affected ears are swollen, erythematous, curled and deformed. Pain is not always apparent and cats are otherwise healthy, although usually FELV- or FIV-positive. Topical or systemic corticosteroids can be used to help reduce the swelling, but in severe cases amputation of the auricles should be considered.

Tumors of the Auricle

The most common tumors of the auricle in cats are squamous cell carcinoma, followed by basal cell carcinoma, hemangiosarcoma, and malignant melanoma.⁵ Most of these tumors are presented as a proliferating, circumscribed mass, but squamous cell carcinoma mimics granulomatous inflammation of the tips of the auricles. In most cases, the preferred treatment is amputation of the entire auricle, pinnectomy.

Pinnectomy

Indications for pinnectomy are malignant tumors (squamous cell carcinoma in cats), severe trauma and pinnal abscesses that have lead to necrosis of the auricle. A skin incision is made around the pinna, near to its attachment to the skull.³ In cats branches of the cranial and caudal auricular vein and caudal auricular artery can be coagulated with electrocautery. Pinnectomy is performed with scissors. The dorsal skin can be advanced over the cartilage edge and sutured to the medial skin with interrupted sutures using absorbable material.

Otitis Media and Interna

Otitis media can develop as an extension of otitis externa through a perforated tympanum, though this is not very commonly seen in cats. Pharyngeal infections may, in rare instances, extend to the middle ear through the auditory tube. Cats usually develop otitis media via an ascending infection from the pharynx as a sequela to upper respiratory tract disease.⁶ Involvement of the middle ear through hematogenous spread is only rarely encountered. Organisms cultured most frequently from affected middle ears include Pseudomonas species, Staphylococcus intermedius, beta-hemolytic Streptococcus, Malassezia, Corynebacterium species, Enterococcus species, Proteus species, E. coli and anaerobes. In cats, bacteria can directly infect the middle and inner ear, which leads to otitis interna with head tilt, nystagmus and ataxia, or the bacteria can produce toxins that inflame the labyrinth.¹ Other causes of otitis media include fungal infections (Aspergillus, Candida), neoplasia, inflammatory polyps, trauma and primary tumors.

The therapy of otitis media and/or interna consists of systemically delivered broad-spectrum antibiotics.⁶ Amoxicillin potentiated with clavulanic acid or enrofloxacin are first-choice antibiotics. Perforated tympanic membranes should close in 4 weeks, when the infection is cured. No ototoxic topical medications should be used when the tympanic membrane is not intact to avoid ototoxicity. When the tympanic membrane is intact, but bulging, a myringotomy could be performed under general anesthesia.

Chronic unresponsive or recurrent otitis media warrants surgical intervention, especially if polyp formation has occurred.⁷ Computed tomography imaging is recommended to evaluate the severity of the disease and the unilateral or bilateral changes of the middle ears that affect surgical planning. Polyps that extend beyond the borders of the tympanic bulla are easily identified on preoperative scans. In some patients removal of the polyp itself is sufficient to eliminate clinical signs. However, a ventral bulla osteotomy may be performed to remove gross exudate and establish drainage from the middle ear and to decrease the changes of recurrence.

Inflammatory Polyp

Nasopharyngeal polyps, also called otopharyngeal or inflammatory polyps, are benign pedunculated growths of uncertain origin but thought to arise as a result of chronic inflammation.⁸ Polyps have been associated with rhinitis and otitis resulting from various bacterial and viral agents, a congenital origin has been suggested as well. They may originate from the mucosal lining of the middle ear, auditory tube and nasopharynx, all of which are similar histologically.⁸ Otopharyngeal polyps occur in cats of any age, although most animals are less than 2 years of age. Polyps in the external or middle ear mimic signs of otitis externa, otitis media or otitis interna.

Otoscopy after flushing may reveal a visible pink or gray smooth, spheric mass occluding the canal. Cytologic or histologic examination of biopsies will reveal the nature of the tissue when diagnosis is not straightforward. Some surgeons perform a ventral bulla osteotomy but recurrence is uncommon with simple traction-avulsion after an incision in the vertical ear canal.³

After aseptic preparation of the surgical site, an incision is made in the skin in a dorsoventral direction over the palpable vertical part of the ear canal, starting just cranioventral to the tragus over approximately 2.5 cm.^2,3 The subcutaneous tissue and parotid gland are dissected with small scissors to free the cartilage of the vertical ear canal to the level of the junction between the auricular and annular cartilages. A vertical stab incision is made from ventral to dorsal in the auricular cartilage just above this junction with a Bard Parker scalpel handle with blade no. 11 over 7–10 mm. Stay sutures are placed on both sides of the incision in the ear canal cartilage with fine monofilament suture material to increase visualisation and avoiding damage to the cartilage. A small closed haemostatic forceps is then introduced into the ear canal, meticulously following the direction of the horizontal ear canal until the polyp is encountered. This forceps is then opened and advanced deeper over the polyp until it can be grasped as close as possible to the osseous meatus. When a firm grip has been achieved, the forceps is gently rotated to make sure no other tissue than the polyp itself has been grasped and traction is applied until the polyp is removed. With complete removal of a classical middle ear inflammatory polyp, a small stalk at the base of the polyp can usually be identified. The middle ear cavity is flushed with warm saline and with a small curette the osseous meatus and most lateral aspect of the tympanic cavity is "palpated" to check for additional inflammatory tissue which is removed with this curette when encountered. The stay sutures are removed and the cartilage of the ear canal is closed with 4-0 monofilament suture material in an interrupted pattern, 3 or 4 knots are usually sufficient. The subcutis is closed in a continuous pattern with 4-0 absorbable monofilament material and the skin is closed in a subdermal suture pattern using the same material.

Ventral Bulla Osteotomy

An incision is made parallel with the midline, centered 2–3 cm toward the affected side from halfway the mandible to the level of the atlas.⁷ The platysma muscle is incised and linguofacial vein is retracted. The incision is deepened by blunt dissection between digastricus muscle and hypoglossal and styloglossal muscles until the bulla can be palpated. A Steinmann pin can be used to make a hole on the ventral aspect, the opening can be enlarged with a small rongeur. In cats both compartments should be opened. Material is collected for culture, sensitivity testing, cytology and histopathology. The cavity is flushed and drained with a Penrose drain. Closure is routine.

References

1.  Haar ter G. Inner ear dysfunction in dogs and cats: conductive and sensorineural hearing loss and peripheral vestibular ataxia. European Journal of Companion Animal Practice. 2007;17:127–135.

2.  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.

3.  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.

4.  Bunge MM, Foil CS, Taylor HW, Glaze MB. Relapsing polychondritis in a cat. Journal of the American Animal Hospital Association. 1992;28:203–206.

5.  Kirpensteijn J. Aural neoplasms. Seminars in Veterinary Medicine and Surgery (Small Animal). 1993;8(1):17–23.

6.  Gotthelf LN. Diagnosis and treatment of otitis media in dogs and cats. The Veterinary Clinics of North America: Small Animal Practice. 2004;20;34(2):469–487.

7.  White RAS. Middle and inner ear. In: Tobias KM, Johnston SA, eds. Veterinary Surgery: Small Animal. St. Louis, MO: Elsevier Saunders; 2012; 2078–2089.

8.  Fan TM, de Lorimier L-P. Inflammatory polyps and aural neoplasia. The Veterinary Clinics of North America: Small Animal Practice. 2004;34(2):489–509.