Diffusion‐ and perfusion‐weighted imaging characteristics of an intracranial abscess in a cat

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Abstract

The images are of a 15-year-old male neutered domestic short-haired cat with a two-day progressive history of inappetence and lethargy. Neurological examination localised a right forebrain lesion with evidence of raised intracranial pressure (hypertension and bradycardia). Magnetic Resonance Imaging was performed with a 1.5 T MRI unit (Philips Ingenia CX, Philips Healthcare, Best, Netherlands,), with details described in Supplementary Data 1. MRI showed a large intra-axial sharply marginated spherical cyst-like mass within the right parietal lobe (Supplementary Fig 1). DWI represented a predominantely restrictive diffusive pattern and PWI significant hypoperfusion of the centre of the mass (Fig 1). The patient underwent a rostrotentorial craniectomy which confirmed imaging findings of an intracranial bacterial abscess, supported by a positive culture and intracellular bacteria in cytological evaluation. Distinguishing between intracranial abscessation, on conventional MRI, from other cystic or necrotic masses can be a challenging process. This feline case is a good example of the typical diffusion and perfusion characteristics that have only been described in human reports. The cavity of a “mature” abscess typically has a highly cellular and viscous composition due to inflammatory cells and bacteria. These features result in a marked restriction of microscopic diffusion of water molecules, resulting in low ADC values. Perfusion-weighted imaging has identified significant hypoperfusion (low relative cerebral blood volume, low relative cerebral blood flow and prolonged mean transit time). This finding can be explained by the reported large amounts of collagen and very low amounts of neovascularisation in intracranial abscesses, leading to a low density of capillary networks within the abscess. The appearance of intracranial bacterial infection in conventional imaging can vary from initial cerebritis developing into the capsular stages. The combination of diffusion- and perfusion-weighted imaging, in addition to conventional MRI, was useful in this case in the diagnosis of an intracranial abscess. Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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