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.

Hydrocephalus is defined as an increased volume of CSF within the cranium, whereas ventriculomegaly refers to enlargement of the ventricles. 12, 22, 23 However, the clinical distinction between the 2 remains challenging. In dogs, ventriculomegaly is considered to be asymptomatic with normal intraventricular pressure, whereas hydrocephalus is a clinically relevant increase in CSF volume compromising the surrounding brain parenchyma. 12, 22 In a recent study, a ventricle:brain index >0.6 together with dorsal deviation of the body of the corpus callosum, periventricular edema, thinning of the sulci, subarachnoid space, or both, and disruption of the internal capsule adjacent to the caudate nucleus was reported to be associated with clinically relevant dilatation of the lateral cerebral ventricles because of increased intraventricular pressure. 12 A similar study has not been performed in cats, and hence, MRI features to distinguish ventriculomegaly from hydrocephalus have not been determined. For consistency, we refer to distension of the ventricles as ventriculomegaly, but acknowledge that a clinically relevant, pathologic increase in CSF volume causing compromise of the surrounding parenchyma is likely to be present in many FIP-affected cats. The finding that increased ventricular size was associated with a more severe clinical presentation and more extensive histopathologic changes supports the likely pathologic relevance of ventriculomegaly. Further studies including a comparison between ventricular dimensions in normal and FIP-affected cats would be valuable. Finally, MRI identified ventriculomegaly in 20 cats, whereas postmortem examination detected ventriculomegaly in only 10 cats, suggesting that high-field MRI may have higher sensitivity for detecting pathologic changes in the ventricular dimensions.