Low-field magnetic resonance imaging of otitis media in two cats: a case report

Abstract

Otitis media is a common disease in clinical veterinary practice. Although low-field magnetic resonance imaging reports for otitis media in dogs exist, in cats detailed information is missing. Radiography is helpful in diagnosing chronic inflammation, but may be insufficient during the initial phase of inflammation. For this reason, this report describes the magnetic resonance findings in two cats with otitis media. In both cases, middle ear empyema was detected. Magnetic resonance imaging of middle ear disorders in cats should contain pre-and post-contrast T1-weighted sequences in the dorsal and transverse planes, a T2-weighted sequence in the dorsal and transverse planes and a fluid-attenuated inversion recovery sequence in the dorsal or transverse planes. On pre-contrast T1-weighted images, the empyema had an intensity similar to that of brain tissue with a delicate hyper-intensity in the middle. On post-contrast T1-weighted images, the material had non-uniform enhancement in the dorsolateral compartment and circumference enhancement in the ventromedial compartment of the tympanic bulla with a hypo-intense centre. On T2-weighted images, the mass had heterogeneously increased signal intensity to brain tissue, but was less intense than cerebrospinal fluid. In the fluid-attenuated inversion recovery sequence, the pathological lesion was distinctly hyper-intense in comparison to other tissues with a narrow area of increased signal intensity in the middle of the ventromedial tympanic bulla compartment. Magnetic resonance imaging is commonly used for the visualisation of different disorders of the membranous labyrinth and allows the differentiation of chronic hematomas, empyemas and middle and internal ear neoplasia. The recommended magnetic resonance protocol of the middle ear should include pre-and post-contrast T1 sequences in the dorsal and transverse planes, the T2 sequence in the dorsal and transverse planes and the fluid-attenuated inversion recovery sequence in the dorsal or transverse planes.