MRI and CT of CNS Cryptococcosis

JAVMA 2023

Else Jacobson, Juan Podadera, Jia Wen Siow, Dennis J. Woerde, Mary F. Thompson, Anna Tebb, Zoe della Valle, David Collins, Richard Malik

Background: Cryptococcosis is a fungal infection that can affect the central nervous system (CNS) of cats and dogs. The imaging features of CNS cryptococcosis in Australian animals have not been well described.

Study: A retrospective, multi-institutional case series of 23 cats and dogs with CNS cryptococcosis and brain MRI or CT studies available for review.

Methods: Brain MRI or CT studies were reviewed by a board-certified radiologist and the imaging findings were characterized and compared between cats and dogs.

Results: The most common imaging findings were meningeal abnormalities, followed by forebrain and cerebellar lesions. Dogs had extra-axial lesions, while cats had intra-axial or extra-axial lesions. Contrast enhancement was present in all cases, with ring enhancement only in cats. Osteolysis was more common in dogs, especially affecting the cribriform plate. Sinonasal or contiguous lesions and locoregional lymphadenomegaly were frequent in both species.

Limitations: The study was limited by the small sample size, the lack of standardized imaging protocols, and the absence of histopathological confirmation of the lesion types.

Conclusions: Imaging lesions in cryptococcal meningoencephalitis were extra-axial in dogs but could be intra-axial or extra-axial in cats. Careful examination for extracranial lesions is important to provide alternative biopsy sites. T2 hypointense lesions, while rare, should prompt consideration of cryptococcosis.

Neuroanatomic locations of extra-axial and intra-axial mass lesions identified on MRI and CT images in 10 cats and 13 dogs with CNS cryptococcosis shown schematically on a normal midline sagittal T2-weighted (T2W) MRI image. Locations of (A) extra-axial lesions in cats, (B) intra-axial lesions in cats, (C) extra-axial lesions in dogs, and (D) intra-axial lesions in dogs are shown. The number of animals affected in each region is depicted by the number in the center of the circle, with larger circles denoting multiple lesions affecting a particular site. Extra-axial regions affected by mass lesions were the olfactory bulbs (1 cat; 5 dogs), the frontal lobe (1 dog), and adjacent to the sphenoid bones (1 cat). Intra-axial regions affected were the parietal lobe (3 cats), temporal lobe (1 cat; 1 dog), occipital lobe (1 cat), cerebellum (2 cats), cerebellopontine angle (1 cat), and pons (1 cat). Some animals had more than 1 lesion (3 cats had multifocal intra-axial lesions, and 1 dog had both an intra-axial and extra-axial lesion). Background images were used with permission from the University of Minnesota Canine Brain MRI Atlas (dog) or Gray-Edwards et al50 (cat)

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