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

Abstract

The ability to differentiate clinical ventriculomegaly from incidental ventricular enlargement remains a challenge in veterinary radiology. Dilatation of one or both olfactory lobe recesses is occasionally seen on MRI of the brain in otherwise normal cats. The purpose of this study was therefore to determine the prevalence of this finding within a population of neurologically normal and neurologically abnormal cats, and to investigate associations with signalment, clinical and neurological examination findings, and MRI features. An observational retrospective cohort study was performed, and archived records were searched for cats that had undergone MRI of the head, including the olfactory lobes. Medical data and MRI parameters were recorded. One hundred fifty-one cats were included, with olfactory recess dilatation present in 56 cats. In 16 neurologically normal cats, olfactory recess dilatation was the only MRI finding. Olfactory recess dilatation was not associated with age, sex, breed, or with the presence of nasal disease. A significant association was found between generalized ventriculomegaly (P = 0.001) and the presence of CSF abnormalities (P = 0.036).Eleven percent of our cohort (16/151) demonstrated olfactory recess dilatation in the absence of other neurological or structural intracranial disease, suggesting that this may be seen as a normal variation in some cats.

The Olfactory Bulb in Companion Animals—Anatomy, Physiology, and Clinical Importance

“…Some brachycephalic cats have a less protuberant OB, with breeds such as Persians described as having shortened OBs that are ventrally and laterally displaced [80], similar to brachycephalic dogs. Dilation of the olfactory recess of the lateral ventricle is identified as an incidental finding in normal cats [70]. In this study, 11% of cats with olfactory recess dilation were clinically normal and, therefore, this dilation was considered an incidental discovery in the absence of other MRI findings.…”

“…In some individuals, the olfactory recess of the lateral ventricle, which is usually an empty virtual space, may become distended with cerebrospinal fluid (CSF). This OB ventricular dilatation has not been associated with ageing in geriatric cats [69,70] despite ageing being associated with generalized ventriculomegaly. In humans, generalized ventriculomegaly associated with an increase in the volume and pressure of the CSF and consequent compres-sion of the adjacent brain tissue is often secondary to changes in fluid drainage associated with a variety of conditions including uncontrolled diabetes mellitus, [71], or as an ex-vacuo effect due to atrophy and loss of neuronal tissue in senility [72].…”

An anatomical and volumetric study on brain ventricles in sheep using different techniques

“…However, in another study, 11% of cats used had enlarged olfactory recesses without any neurological or structural disease. According to this finding in the study, it is thought that bulbus olfactorius dilatation in some cats can be seen as a normal variation (McGregor et al, 2023). In our study on healthy Akkaraman sheep, it was determined that this dilatation, which was thought to be non‐pathological, was present in 100% of the sheep examined.…”

“…The computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography models of sheep are simple to use (Nitzsche et al, 2016). On brain MR images of cattle (Schmidt et al, 2009), domestic ruminants (Schmidt et al, 2012), equines (Stuckenschneider et al, 2014), sheep (Ella et al, 2017; Gerussi et al, 2022; Nitzsche et al, 2015; Peruffo et al, 2019), cats (McGregor et al, 2023) and humans (Acer et al, 2010; Gerussi et al, 2022), structural and measurement findings have been successfully evaluated.…”