Herpes simplex type 2

Radiological appearance:

-CT: Hypo dense lesion in CT.

-MRI: T1 hypo intense, T2 hyper intense, FLAIR hyper intense.

-All the above mentioned pictures are characterized by specific location which is the temporal lobe or area of insula (this location is specific for that lesion).

-Could be bilateral and symmetrical or not.

-Could be hemorrhagic.

-Usually no contrast enhancement.

-Diffusion sequence is one of the most important way to differentiate between infection and tumors where infection usually has restricted diffusion (hyper intense) while tumors are usually free of diffusion( intensity is similar to that of the CSF). Do not forget the clinical as one of the most important factor in differentiating between infection and tumors where in the former there is fever and semi conscious state while in the latter there is headache.
-Encephalitis with or without treatment will cause post encephalitic sequel which consists of the following:
*Encephalomalacia.
*Brain atrophy.
*Calcification.

Herpes simplex virus affecting right temporal lobe seen in this T2 image

Diffusion weight image shows restricted diffusion in both temporal lobes more on the right side.