The Dark Side of Seizure: Case Series of a T2 Dark-Through Pattern of Peri-ictal Diffusion Restriction

Analogous to T2 shine-through, T2 hypointensity can "dark-through" on diffusion weighted imaging (DWI) and mask diffusion restriction. In such cases, diffusion restriction is evident only by apparent diffusion coefficient (ADC) hypointensity, which is often subtle and easily missed without corresponding DWI hyperintensity. Because diffusion restriction may be present in the setting of seizure, avoiding this pitfall can aid in seizure diagnosis for patients without any other magnetic resonance imaging (MRI) findings. We present a case series of nine patients in the peri-ictal period with T2 dark-through on MRI to raise awareness of this finding and its potential clinical role.