An eight year old having fever for 5-6 days along with vomiting  episode of facial twitch and clinching teeth. conscious. CBC WNL,DENGUE NS1 POSITIVE, P VIVAX POSITIVE, WIDAL POSITIVE, TYPHI DOT NEGATIVE, URINEWNL,LFT WNL.SGPT 148.

MRI-SMALLT2 FLAIR HYPERINTENSITY FOCUS IN LEFT THALLAMUS REGION WITH MILD DIFFUSE BRAIN EDEMA S/O POSSIBLE VIRAL ENCEPHALITIS. What could be cause of brain edema and  hyperintensity focus in left thalamus  region?