D.D.using DWI

Click to enlarge

If you are facing a case with free diffusion, give contrast, if no enhancement, you are facing a case of arachnoid cyst or non enhancing tumor such as infiltrating glioma, diffuse glioma or brain stem glioma, the former has intensity like CSF and is an extra axial lesion while the latter has intensity more than that of CSF and is located intra axially.

If you got enhancement, it will be a tumor.

If the result is restricted diffusion, now you are facing with one of four choices

-Infection which shows no cortical location or vascular territory distribution.

-Infarction which shows cortical location and vascular territory distribution.
-High cellular tumor.

-Or epidermoid cyst which is a extra axial lesion while infection and infarction affecting the brain itself(intra axial). 

Click to enlarge