Prevalence and clinical correlations of olfactory recess dilatation in MRI studies of the feline brain

Ombeline McGregor, Marie-Aude Genain, Timothy Lee Williams, Lisa Alves

Background: The authors describe the challenge of distinguishing clinical ventriculomegaly from incidental ventricular enlargement in cats. They also review the literature on olfactory recess dilatation, which is a rare finding in cats that may be associated with hydrocephalus or other intracranial diseases.

Study: The authors conducted a retrospective cohort study to determine the prevalence and clinical correlations of olfactory recess dilatation in cats that underwent MRI of the head. They compared cats with and without olfactory recess dilatation in terms of signalment, clinical and neurological examination findings, CSF analysis results, and other MRI features.

Methods: The authors included 151 cats that had MRI of the head, including the olfactory lobes, between 2014 and 2021. They recorded medical data and MRI parameters, and performed statistical analyses to assess the association between olfactory recess dilatation and various variables.

Results: The authors found that 56 cats (37%) had olfactory recess dilatation, which was bilateral in 21 cats (38%) and unilateral in 35 cats (62%). They also found that olfactory recess dilatation was significantly associated with generalized ventriculomegaly (P = 0.001) and CSF abnormalities (P = 0.036), but not with age, sex, breed, neurological abnormalities, space-occupying intracranial disease, or nasal disease. They reported that 16 cats (11% of the total population) had olfactory recess dilatation without any neurological or structural intracranial disease.

Limitations: The authors acknowledged the limitations of their retrospective study, such as the lack of standardized MRI protocols, the absence of histopathology, and the unavailability of long-term follow-up data. They also noted that intraventricular pressure was not measured in any of the cats, and that olfaction was not routinely tested in small animals.

Conclusions: The authors concluded that olfactory recess dilatation in cats was correlated with generalized ventriculomegaly and CSF abnormalities, and that it may be seen as a normal variation in some cats without neurological or structural intracranial disease. They suggested that future studies with long-term outcome assessments are needed to further evaluate the clinical relevance of this MRI finding.

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