Computed tomographic findings in 205 dogs with clinical signs compatible with middle ear disease: a retrospective study.

BACKGROUND: Computed tomography (CT) is considered to be the reference method to evaluate middle ear structures.

OBJECTIVES: To evaluate the presence and severity of CT changes in the middle ear and establish if any specific clinical presentations are associated with otitis media.

ANIMALS: Medical records of animals referred for CT with history and clinical signs consistent with middle ear disease.

METHODS: Retrospective evaluation of CT examinations of tympanic bullae performed over a six year period. Medical records were reviewed for signalment, clinical signs and cytological evaluation of the external ear canal. Dogs were divided into three clinical groups: chronic otitis externa (Group 1), peripheral vestibular disorder (Group 2) and other clinical presentations (Group 3).

RESULTS: Group 1 - Of 214 ears, 87 (40.7%) had CT abnormalities: 38 of 87 (17.7%) had material-filled bullae, 42 of 87 (19.6%) had thickened bullae walls and seven of 87 (3.2%) had lysis of the bulla. Abnormalities were significantly more frequent in dogs with suppurative otitis than in erythemato-ceruminous otitis (57% and 23%, respectively; P = 0.003). Proliferative otitis, particularly in French bulldogs, was associated with severe otitis media. Group 2 - Of the 106 ears, 91 (85.8%) had normal tympanic bullae. Group 3 - Of the 26 ears from deaf dogs, 17 had filled bullae; all nine affected dogs were Cavalier King Charles spaniels. All dogs with Claude Bernard Horner syndrome or head tilt had normal tympanic bullae.

CLINICAL SIGNIFICANCE: CT is useful for canine chronic otitis externa, particularly in suppurative or proliferative otitis, even in the absence of associated neurological signs.