Diffusion restriction is classically associated with ischemic stroke, though similar changes can be seen with focal seizure and venous congestion. Few studies highlight the presence of cytotoxic cerebral edema with cortical diffusion restriction that can present on imaging with seizures as well as venous congestion. History can help to make the correct diagnosis in these cases. 

A 57-year-old female with a history of chronic migraines, breast cancer in remission, and generalized tonic-clonic seizures in 2010, on phenytoin, presented with two weeks of right-sided headache with flashing lights and impaired vision in her left visual field. MRI brain without contrast showed diffusion restriction over the right occipital lobe cortex with corresponding restriction in the nearby white matter, concerning for cytotoxic cerebral edema. She was admitted for suspected acute ischemic stroke. Physical exam revealed a left homonymous hemianopia, though the patient also reported continued flashing lights and palinopsia. Given the positive visual symptoms, there was concern for seizure rather than stroke. Video EEG demonstrated frequent right occipital lobe seizures corresponding to the patient’s symptoms. There was additional concern on imaging for dilated venous sinuses around the area of diffusion restriction raising the possibility of cerebral venous sinus thrombosis in the confluence versus a dural arteriovenous fistula with venous congestion as a possible cause of focal seizure. MRV and CTV were unremarkable. DSA similarly did not demonstrate any thrombus or vascular malformation. Repeat imaging demonstrated resolution of DWI changes with residual T2 FLAIR hyperintensity thought to be due to focal cortical dysplasia. 

This case highlights the importance of pursuing alternative diagnoses for diffusion restriction in the setting of the appropriate clinical history. Positive visual symptoms are rare in ischemia and more commonly associated with seizures. Further work up ruled out venous thrombus, with focal cortical dysplasia as the likely seizure focus.