Peri-ictal magnetic resonance imaging characteristics in dogs with suspected idiopathic epilepsy

BACKGROUND: The pathophysiology of changes in magnetic resonance imaging (MRI) detected after a seizure is not fully understood.

OBJECTIVE: To characterize and describe seizure-induced changes detected by MRI.

ANIMALS: Eighty-one client-owned dogs diagnosed with idiopathic epilepsy.

METHODS: Data collected retrospectively from medical records and included anatomical areas affected, T1-, T2-weighted and T2-FLAIR (fluid-attenuated inversion recovery) appearance, whether changes were unilateral or bilateral, symmetry, contrast enhancement, mass effect, and, gray and white matter distribution. Diffusion- and perfusion weighted maps were evaluated, if available.

RESULTS: Seizure-induced changes were T2-hyperintense with no suppression of signal on FLAIR. Lesions were T1-isointense (55/81) or hypointense (26/81), local mass effect (23/81) and contrast enhancement (12/81). The majority of changes were bilateral (71/81) and symmetrical (69/71). The most common areas affected were the hippocampus (39/81) cingulate gyrus (33/81), hippocampus and piriform lobes (32/81). Distribution analysis suggested concurrence between cingulate gyrus and pulvinar thalamic nuclei, the cingulate gyrus and parahippocampal gyrus, hippocampus and piriform lobe, and, hippocampus and parahippocampal gyrus. Diffusion (DWI) characteristics were a mixed-pattern of restricted, facilitated, and normal diffusion. Perfusion (PWI) showed either hypoperfusion (6/9) or hyperperfusion (3/9).

CONCLUSIONS AND CLINICAL IMPORTANCE: More areas, than previously reported, have been identified that could incur seizure-induced changes. Similar to human literature, DWI and PWI changes have been identified that could reflect the underlying metabolic and vascular changes.