JAVMA, Vol 244, No. 1, January 1, 2014 Vet Med Today: What Is Your Diagnosis? 37

History

A 4-year-old neutered male Tonkinese cat was evaluated at the University of Queensland Small Animal Clinic and Veteri-nary Teaching Hospital because of a swelling under the right mandible, first noticed by the owner that morning. The patient was otherwise well. There was a fluctuant, nonpainful swelling approximately 3 cm in diameter under the right mandible at the angle of the jaw. Examination of the right ear revealed some black debris in the external ear canal, underneath which was puru-lent exudate. Cytologic examination of a fine-needle aspirate sample from the fluctuant swelling was diagnostic for an abscess. There were no other abnormalities on clinical examination, so the patient was administered a long-acting antimicrobial SC, with general anesthesia and surgical investigation planned in 5 days. When the cat was returned to the clinic, the submandibu-lar abscess had ruptured. A pink to red fleshy mass could now be seen protruding from the middle ear through the tympanic membrane. Results of a CBC and serum biochemical analysis were within reference limits. The patient was anesthetized, and the tympanic bullae and ear canals were examined by means of CT; pre- and postcontrast images were obtained (Figure 1).

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

This report was submitted by Alana J. Rosenblatt, BVSc; Sarah J. Zito, BVetMed; and Natalie S. Webster, BVSc; from the School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia (Rosenblatt, Zito); and Adelaide Veterinary Specialist and Referral Centre, 102 Magill Rd, Norwood, SA 5067, Australia (Webster). Dr. Rosenblatt’s present address is Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

Address correspondence to Dr. Rosenblatt (ajr293@cornell.edu).

What Is Your Diagnosis?

Figure 1—Transverse CT images (slice thickness, 1 mm) of the head of a 4-year-old neutered male Tonkinese cat with a right submandibular swelling and right-sided otor-rhea. A—Precontrast CT image at the level of the external ear canals, acquired with a soft tissue algorithm (window width, 280 Hounsfield units [HU]; window level, 40 HU). B—Precontrast CT image at the level of the tympanic bullae, acquired with a bone algo-rithm (window width, 2,500 HU; window level, 500 HU). C—Precontrast CT image of the tympanic bullae at the same slice location as D, for comparison, acquired with a soft tissue algorithm (window width, 280 HU; window level, 40 HU). D—Postcontrast CT image of the tympanic bullae at the same slice location as C, for comparison, acquired with a soft tissue algorithm (window width, 250 HU; window level, 50 HU).

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38 Vet Med Today: What Is Your Diagnosis? JAVMA, Vol 244, No. 1, January 1, 2014

Diagnostic Imaging Findings and Interpretation

Heterogeneous soft tissue–dense material occu-pies the entire right tympanic cavity and horizontal ear canal (Figure 2). The tympanic bulla is expanded and irregular, with multiple sites of osteolysis. Soft tissue swelling is present lateral and ventral to the right bulla, involving the right horizontal ear canal and extending as far caudally as C1. The postcontrast scan reveals a 0.9-cm-diameter mass with strong, homogeneous con-trast enhancement, located in the dorsomedial portion of the right tympanic cavity. It originates from the loca-tion of the opening of the auditory (Eustachian) tube and is surrounded by predominantly non–contrast-enhancing soft tissue–dense material. The contrast-enhancing mass does not extend into the nasopharynx or external ear canal. There is patchy, strong contrast enhancement throughout the right submandibular soft tissues surrounding the right bulla and involving the lateral wall of the external aural canal.

The origin, location, and pattern of contrast enhance-ment of the middle ear mass in this patient suggest a di-agnosis of unilateral inflammatory polyp.1 There is severe, chronic otitis media presumed secondary to obstruction of the auditory tube and external ear canal, with osteolysis

of the tympanic bulla, and subsequent abscess formation into the surrounding periauricular tissues. A neoplastic mass, such as squamous cell carcinoma, lymphoma, ceruminous gland adenocarcinoma, or sebaceous adenoma, was also considered as a differential diagnosis for the middle ear mass.

Treatment and Outcome

A right ventral bulla osteotomy, followed by curettage and drainage of the bulla, was performed to remove the mass. Samples of the purulent fluid from the bulla were obtained and submitted for bacteriologic culture and antimicrobial susceptibility testing. The ven-tral aspect of the tympanic bulla was removed and submitted for bacteriologic culture. The mass in its entirety was submitted for histo-logic evaluation. Recovery from anesthesia was uneventful; however, signs of Horner’s syndrome were present for 6 days after surgery.

Histologic evaluation results confirmed the presumptive imaging diagnosis of an in-flamed nasopharyngeal polyp. A heavy pre-dominant growth of Pasteurella spp was seen on bacteriologic culture; the patient was sub-sequently started on a 2-week oral course of amoxicillin and clavulanic acid. The cat was clinically normal at recheck consultations 2 weeks and 12 months after hospital discharge.

Comments

To the authors’ knowledge, this is the first reported case of a cat with an inflam-matory polyp with a submandibular swell-ing as the primary clinical sign. At initial

consultation, the cat was also found to have otor-rhea, which had not been noticed by the owner. None of the other commonly reported clinical signs result-ing from obstruction of the ear canal or nasopharynx by an inflammatory polyp, such as respiratory stertor or stridor, sneezing, nasal discharge, dyspnea, dys-phagia, or voice change,2,3 were identified at the first evaluation.

Radiography, although readily available in prac-tice, is less sensitive than CT and MRI in the diag-nosis of middle ear disease.4 Computed tomography and MRI are complementary cross-sectional imaging techniques of the external, middle, and inner ear, with CT allowing better visualization of bony structures.4 In the cat of this report, the appearance of a thickened right tympanic bulla when displayed in a narrow (soft tissue) window is artifactual, caused by adjacent fluid in the bulla,5 and is not present when the bulla is dis-played in a wide (bone) window. The administration of iodinated contrast medium IV with CT of the bullae allows differentiation of living tissues from nonliving tissue or fluid. Computed tomography can facilitate identification of the anatomic location and extent of an aural mass, in addition to defining the extent of osseous bulla involvement3; this information assists surgical planning for successful removal of the mass.

Figure 2—Same CT images as in Figure 1. Soft tissue–dense material (45 HU) occupies the entire right tympanic cavity and horizontal ear canal (asterisks; A); compare with the normal left bulla and ear canal. There is swelling of the right periauricular soft tissues (arrows; A). The right tympanic bulla is expanded and ir-regular, with sites of osteolysis (arrow; B). Notice the strongly contrast-enhancing mass (155 HU) located in the dorsomedial aspect of the right tympanic cavity (hashmark; D), which is clearly demarcated from the other soft tissues and fluid in the bulla. There is marked contrast uptake of the periauricular soft tissues, includ-ing the wall of the external ear canal (arrows; D).

JAVMA, Vol 244, No. 1, January 1, 2014 Vet Med Today: What Is Your Diagnosis? 39

Use of CT with contrast medium in the cat of the pres-ent report allowed identification of the inflammatory polyp, tympanic bulla osteolysis, and extension of the otitis media into the periauricular tissues. Further-more, use of contrast medium can help identify any CNS extension of otitis media.6 For these reasons, it may be beneficial to include a postcontrast series as part of the standard protocol for CT examination of the tympanic bullae.

1. Drees R. External, middle and inner ear. In: Schwarz T, Saun-ders J, eds. Veterinary computed tomography. West Sussex, Eng-land: John Wiley & Sons Ltd, 2011;153–160.

2. Anderson DM, Robinson RK, White RAS. Management of in-flammatory polyps in 37 cats. Vet Rec 2000;147:684–687.

3. Sietz SE, Losonsky JM, Marretta SM. Computed tomographic appearance of inflammatory polyps in three cats. Vet Radiol Ultrasound 1996;37:99–104.

4. Garosi LS, Dennis R, Schwarz T. Review of diagnostic imag-ing of ear diseases in the dog and cat. Vet Radiol Ultrasound 2003;44:137–146.

5. Barthez PY, Koblik PD, Hornof WJ, et al. Apparent wall thickening in fluid filled versus air filled tympanic bulla in computed tomog-raphy. Vet Radiol Ultrasound 1996;37:95–98.

6. Cook LB, Bergman RL, Bahr A, et al. Inflammatory polyp in the middle ear with secondary suppurative meningoencephalitis in a cat. Vet Radiol Ultrasound 2003;44:648–651.