Abstract
BackgroundThe pathophysiology of changes in magnetic resonance imaging (MRI) detected after a seizure is not fully understood.ObjectiveTo characterize and describe seizure‐induced changes detected by MRI.AnimalsEighty‐one client‐owned dogs diagnosed with idiopathic epilepsy.MethodsData 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.ResultsSeizure‐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 ImportanceMore 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.
Highlights
Magnetic resonance imaging (MRI) can identify seizure-induced changes in the ictal and early postictal stages of seizure activity.[1]
Quantitative values were obtained from the apparent diffusion coefficient (ADC), Relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), and mean transit time (MTT) maps
They were obtained by manually drawing up to 3 regions of interest (ROIs) in each affected area identified on conventional imaging (T2-fluid-attenuated inversion recovery (FLAIR)) and formulating a mean value
Summary
Magnetic resonance imaging (MRI) can identify seizure-induced changes in the ictal and early postictal stages of seizure activity.[1]. It has been proposed that to compensate for this increase in metabolic demand, compensatory regional hyperperfusion occurs.[2] should sustained ictal activity persist, these compensatory mechanisms are no longer sufficient. This leads to hypoxia, lactic acidosis and failure of cellular homeostasis causing cellular swelling and increased membrane permeability. The cascade of metabolic changes subsequently leads to the formation of cytotoxic and vasogenic edema, a finding supported by experimentally induced seizures in rats.[3] The formation of identifiable changes has been documented as time-dependent[4]; especially dependent on duration of ictal activity. We aimed to report if any changes were seen on diffusion- and perfusion-weighted imaging
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