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.

The signalment, physical and neurologic examination findings, clinicopathologic test results, diagnostic imaging findings, and histopathologic findings were recorded. Magnetic resonance images were acquired on 5 MRI systems, all of which were highfield-strength magnets (1.5 Tesla). The evaluation of MRI included the CNS region imaged and all surrounding structures. The MR images were evaluated by a board-certified neurologist (EB) and a neurology resident in training (AC) blinded to the clinical signs. All studies included both spin echo or turbo spin echo T1-weighted (T1W: repetition time [TR] 461-992 ms; echo time [TE] 15-20 ms; slice thickness, 2.5-5.0 mm), and spin echo or turbo spin echo T2-weighted (T2W: TR 2,500-9,000 ms; TE 80-119 ms; slice thickness, 2.5-5.0 mm) images. T1-weighted (T1W) images were acquired before and after IV administration of gadolinium contrast material (0.1 mmol/kg gadobutrol a or gadopentetate dimeglumine b ). A group of these studies included T2-weighted fluid attenuation inversion recovery (T2W-FLAIR: TR 5,600-35,000 ms; TE 90-119 ms; slice thickness, 2.5-5.5 mm) images and T2* gradient recall echo (T2*: TR 840-1,021 ms; TE 80-119 ms; slice thickness, 4.0-5.0 mm) images. Findings were categorized as mild (focal regions of contrast enhancement of meninges, ependyma, or both without ventriculomegaly, mass effect, or dilatation of the central canal), moderate (mild ventriculomegaly with minimal mass effect and multifocal regions of contrast enhancement), or severe (marked ventriculomegaly with moderate-to-severe mass effect, dilatation of the central canal, and multifocal to generalized contrast enhancement). To provide a quantitative measure of the extent of ventriculomegaly, the maximum height of the fourth ventricle was recorded as a percentage of the caudal fossa brain height (cerebellum and brainstem) on midline sagittal T2W images (Fig. 1) . The maximum height of the lateral ventricles at the level of the interthalamic adhesion was recorded on transverse T2W images as a percentage of the brain height at that level (Fig. 2) . The height of the brain on both views was measured from a line drawn parallel and immediately adjacent to the line measuring the ventricle height.