Stephanie Phillipps ^* Rita Goncalves

• University of Liverpool, Liverpool, United Kingdom

Epilepsy is one of the most common chronic neurological conditions affecting dogs. Previous research exploring the likelihood of a structural cause of epilepsy specifically in dogs with a normal inter-ictal examination is limited to a small population of dogs using lowfield MRI. The aims of this study were to establish high-field (1.0 and 1.5T) MRI findings in dogs presenting with epileptic seizures and a normal inter-ictal examination.Medical records were retrospectively searched for dogs presenting with at least two epileptic seizure events more than 24 hours apart. To be included in the study, patients had to have a normal neurological examination, high-field MRI of the brain and have had metabolic and toxic causes excluded.Four hundred and twelve dogs were eligible for inclusion. Crossbreeds were most commonly affected (n=63, 15.3%) followed by Border collies (n=39, 9.5%) and Labrador retrievers (n=26, 6.3%). Seventy-six dogs (18.5%) had abnormalities detected on MRI, 60 (78.9%) of which were considered to be incidental. Overall, 16 dogs (3.9%) had a structural cause of their epileptic seizures including neoplasia (n=13, 81.3%), anomalous (n=2, 12.5%) and meningoencephalitis of unknown origin (MUO) (n=1, 6.3%). When split into age group at first epileptic seizure structural lesions were documented in 0/66 dogs aged <1 year, 4/256 (1.6%) dogs aged ≥1 year ≤6 years (three neoplastic and one anomalous), 3/51 (5.9%) aged >6 years ≤8 years (two neoplastic and one MUO), and 9/39 (23.1%) dogs aged >8 years (eight neoplastic, one anomalous). Multivariate analysis identified two risk factors for structural disease: increasing age at first epileptic seizure (p <.001, OR = 4.390, CI 2.338-8.072) and a history of status epilepticus (p = 0.049, OR = 4.389, CI 1.010-19.078).Structural lesions are an uncommon cause of epilepsy at any age in dogs with a normal interictal examination.