Clinicopathologic Features and Magnetic Resonance Imaging Findings in 24 Cats With Histopathologically Confirmed Neurologic Feline Infectious Peritonitis

Crawford, A.H.; Stoll, A.L.; Sanchez-Masian, D.; Shea, A.; Michaels, J.; Fraser, A.R.; Beltran, E.

Magnetic resonance imaging identified abnormalities within the brain, spinal cord, or both in all 24 cats. Marked vasculitis, typically affecting the leptomeninges, ependyma, and choroid plexuses, was visualized in all cats with high-field MRI after administration of IV contrast agent. In 2 cases, the only detected MRI abnormality was meningeal contrast enhancement of the cervical spinal cord, emphasizing the importance of contrast administration in any case in which FIP is suspected. A previous study reported normal MRI findings in 3 of 8 cats with neurologic FIP. 10 The cats in this previous study underwent MRI of the brain only, and hence, the presence of spinal cord meningeal contrast enhancement and syringomyelia may not have been fully evaluated. However, evaluation of meningeal contrast enhancement in MRI studies in the cat can be challenging, particularly in the absence of associated parenchymal lesions. The assessors of the MR images in our study were blinded to the clinical signs of the cats, but they were not blinded to the final diagnosis of neurologic FIP. In contrast, the previous study included various types of feline meningoencephalitis that may not be associated with vascular and superficially orientated inflammation, and thus, the authors may have been more cautious in identifying pathologic contrast enhancement of the meninges on MRI. 10 Quantitative measures of the degree of contrast enhancement would be very useful to overcome this source of bias.