N13 - Frequency of MRI Abnormalities in a Population of Dogs Referred to Veterinary Neurologists

Abstract: Background – Frequency of findings in canine brain magnetic resonance imaging (MRI) after referral to neurologists has not been reported. Multiple studies have focused on radiologist interpretations without association to confirmed neurological dysfunction.

Hypothesis/Objectives – Study objectives were to determine frequency of brain MRI findings in dogs with signs of intracranial disease from two referral institutions and agreement between neurologists reviewing MRIs. We hypothesized there would be no difference in frequency of MRI findings between institutions and neoplastic lesions would be the most frequent MRI diagnosis.

Animals – A cohort of 300 randomly selected dogs undergoing brain MRI to determine underlying cause of primary neurological presentations.

Methods – Medical records of dogs from two tertiary-care institutions were collected retrospectively from 2014-2019. Brain MRIs were reviewed blindly/independently by two ACVIM board-certified neurologists. Lesion characteristics and suspected MRI diagnosis based on published criteria were described.

Results – An intracranial MRI abnormality was determined in 64-71% of cases. Neoplastic (38-42%) and inflammatory (26-33%) lesions were the most common differentials. Seizures were noted in 52% of cases; 31% of dogs with seizures had normal MRIs. Interobserver agreement on abnormal scans was considered very good (Κ=0.764)

Conclusions and clinical importance – At least 29% of dogs with intracranial disease have normal MRIs. The ability of neurologists to differentiate and agree on normal versus abnormal MRIs is very good. Neoplastic and inflammatory were the most common MRI diagnoses. This data may help guide discussion with clients on expectations before imaging, and aid in empiric therapy decisions.