MAGNETIC RESONANCE IMAGING FINDINGS IN 80 DOGS WITH FOREBRAIN TUMOURS

This multicentric retrospective study aim to describe the magnetic resonance imaging (MRI) findings of forebrain tumors in 80 dogs. Medical records from two specialised centres were retrospectively analysed over a two-year period (2022-2024). All subjects with a complete medical history and diagnostic confirmation by MRI of forebrain tumors were included in the study. For each tumor, the type (intra- or extra- axial), different brain erniation (BH) such as midline shift (MS), subfalcine herniation (SFH), caudal trans-tentorial herniation (CTH) and foraminal herniation (FMH), and secondary signs such as lateral ventricular compression, displacement of the quadrigeminal lamina and presence of perilesional edema were recorded. A quantitative analysis of the parametric data regarding tumour location and the distribution frequency for the sex variable and the frequency of BH were calculated on the total number of dogs included. A one-way analysis of variance (ANOVA) was then applied to lesion size, grouping tumours according to the presence of edema only (Group I - G1), compression only (Group II - G2), edema and compression (Group III - G3), and neither edema nor compression (Group IV - G4). Pearson's correlation and linear regression were used to verify the correlation between lesion size, animal age and skull size. Finally, a point-biserial correlation was used to find the correlation between lamina displacement and lesion size. Tumours were intra-axial in 43 (53.75%) dogs and extra-axial in 37 (46.25%) dogs. Intra-axial lesions were found in 25 (53.13%) males and 18 (41.47%) females. Extra-axial lesions were found in 18 (48.65%) males and 19 (51.35%) females. Of the dogs included in the study, 87.50% had MS, 28.75% had CTH, 27.50% had FMH, and 77.50% had SFH. Regarding the MRI signs recorded, 16.25% had only one sign, 53.75% had two signs, 13.75% had three signs, and 16.25%% had four signs. The 57.50% of dogs had lamina dislocation and of these 16.25% had edema only, 8.75% had compression only, 67.50% had edema plus compression, and 5% had neither edema nor compression. The lesion size was 4.08±3.18 cm3 in G1, 3.93±1.86 cm3 in G2, 4.14±2.82 cm3 in G3 and .32±0.87 cm3 in G4. No statistical differences in lesion sizes were found by one-way ANOVA. Pearson correlation and linear regression showed no correlation between lesion size and animal age (p>0.05; r=-0.18) and a positive correlation between lesion size and skull size (p=0.009; r=0.29). In addition, point- biserial correlation showed a positive correlation between lesion size and caudal displacement of the quadrigeminal lamina (p=0.02; r=0.28), particularly in G1 (p=0.03; r=0.58) and G2 (p=0.02; r=0.80). Despite clinical implications of different BH in dogs are still unclear, clinical signs supportive of BH might not consistently be present (1-2). For these reasons is important to recognize MRI signs of BH. This study provides a detailed characterization of MRI findings in dogs with forebrain tumors, highlighting key associations between lesion type, different BH and secondary signs and may aid in refining diagnostic and prognostic assessments during forebrain tumor in dogs.