Imaging findings in otitis media and resulting secondary lesions in dogs and cats – an image essay

Abstract

Over the past 2 decades, the increasing availability of computed tomography (CT) and magnetic resonance imaging (MRI) as well as the growing professional expertise have significantly improved the diagnostics of middle and inner ear diseases in dogs and cats. In answering some of the diagnostic questions, CT and MRT demonstrate equivalent performance. For most questions, however, there are differences in the diagnostic performance due to the physical imaging properties of the 2 modalities.

CT is more sensitive in demonstrating involvement of the bulla wall and is more effective for detecting abnormal content within the tympanic bulla. In addition, with CT it is often easier to guide tissue samplings. On the other hand, structural changes of the soft tissues of the skull, head, meninges, brain, and nerves are not or only insufficiently detectable on CT images. MRI is clearly superior here. Therefore, MRI is essential for the characterization of materials inside the bulla cavity and for demonstrating the extent of any central spread of otitis media (OM).

In this image essay, CT and MRI features of OM and resulting secondary lesions described in the literature are analyzed and summarized. Own image examples are used for illustration. Information on the etiology, pathogenesis, pathomorphology, and clinical signs important for understanding these changes are presented in concise descriptions.

Zusammenfassung

Über die letzten 2 Jahrzehnte haben die zunehmende Verfügbarkeit von Computertomografen (CT) und Magnetresonanztomografen (MRT) sowie die gewachsene fachliche Expertise die Diagnostik von Mittel- und Innenohrerkrankungen bei Hunden und Katzen erheblich verbessert. Bei der Beantwortung von einer Reihe diagnostischer Fragestellungen können CT und MRT als gleichwertige Verfahren angesehen werden. Bei anderen Fragestellungen wiederum bestehen Unterschiede in der diagnostischen Leistungsfähigkeit aufgrund der physikalischen Abbildungseigenschaften. Sensitiver ist die CT bei der Darstellung von Veränderungen der Bullawand. Die CT ist auch das effektivere Verfahren, wenn abnormaler Inhalt in der Bulla tympanica nachgewiesen werden soll. Darüber hinaus ist es mit der CT oft einfacher, die Entnahme von Gewebeproben zu planen und durchzuführen. Andererseits sind strukturelle Veränderungen der Weichteile des Kopfes, der Meningen, des Gehirns und von Nerven in der CT nicht oder nur unzureichend erkennbar. Hier ist die MRT klar überlegen. Daher ist die MRT für die Typisierung von Materialen in der Bulla sowie die Darstellung des Ausmaßes einer eventuell existierenden zentralen Ausbreitung einer Otitis media (OM) unerlässlich.

In diesem Bildessay werden die in der Literatur beschriebenen bildmorphologischen Merkmale einer OM und die durch sie bedingten sekundären Pathologien analysiert und zusammengefasst. Eigene Bildbeispiele dienen der Illustration. Für das Verständnis der Veränderungen wichtige Informationen zur Ätiologie, Pathogenese, Pathomorphologie und dem klinischen Erscheinungsbild werden in kurzer Form dargestellt.

Keywords

Computed tomography - magnetic resonance imaging - dog - cat - otitis media

Schlüsselwörter

Computertomografie - Magnetresonanztomografie - Hund - Katze - Otitis media

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