Purpose:
Stroke mimics constitute between 10 to 30% of acute stroke presentations. Imaging, particularly MRI helps exclude a large number of these. Several however, demonstrate restricted diffusion on MRI and remain difficult to differentiate from stroke both clinically and on imaging. The purpose of this review is to describe a pattern based approach to stroke mimics on diffusion weighted imaging (DWI) to aid easier recognition and diagnosis. 

Approach/Methods:
With the advent of endovascular therapy as standard of care for hyperacute stroke, magnetic resonance imaging (MRI) for stroke has increased in volume and reporting has become time-sensitive. "Time is brain", mandates both accurate and fast reporting.This is invariably on a background of incomplete/ inadequate clinical data in the emergent setting. Additionally limited stroke MRI protocols while adequate for the diagnosis of infarcts, may be somewhat limited in characterizing mimics. We compare known stroke mimics to the characteristic diffusion weighted imaging (DWI) appearances of the different subtypes of stroke including thrombotic, embolic and hypoxic injury. We include both common and less common conditions with typical and atypical findings, as well as rare conditions with characteristic imaging appearances. 


Findings/Discussion:
Ischemic stroke subtypes demonstrate specific patterns on DWI. Thrombotic vascular occlusion classically demonstrates restricted diffusion confined to defined arterial territories. Mimics include tumours and large abscesses. Typical mimics of embolic strokes which are usually multiple and small, involving more than one arterial territory (commonly bilateral), include microabscesses/septic emboli and hemorrhagic metastases. We also demonstrate a case of meningitis simulating embolic stroke. Mimics of hypoxic injury with cortical restricted diffusion including postictal changes and encephalitis. We also demonstrate acute thrombus in a cortical vein mimicking cortical stroke and rarer causes such as Creutzeld Jakob disease and heat stroke. Specific imaging patterns such as bilateral infarcts seen in internal cerebral vein thrombosis simulating artery of Percheron occlusion, as well as the rarer Balo's concenteric sclerosis and neuronal inclusion disease (NIIDS) with characteristic patterns on DWI are also included. 

Summary/Conclusion:
A pattern specific description of stroke mimics, aims to stratify the possible differentials for acute stroke in a manner that will help aid easier diagnosis for the busy on-call radiologist.

A Pattern Based Approach to Stroke Mimics on MRI

[Virtual Conference Page](https://event.vconferenceonline.com/microsite/html/login.aspx?id=1551&rlp=1)

[ASNR Website] (https://www.asnr.org//annualmeeting)

[ePosters](https://www.morressier.com/event/asnr2020eposter/5e5d0b2c35f8e2df5e55a268)