Appears hypoattenuating on CT and hyperintense on FLAIR
Varieties include
1. Cytoxic - caused by NA/K pump dysfunction most commonly swelling of INTRAcellular space then progresses to IONIC edema wherein fluid moves to intravascular space - leads to restricted diffusion on MR / loss of gray-white differentiation on CT
2. Vasogenic - BBB breakdown or caused by neoplasm or infection or inflammation or hem orrhage or infarct
3. Intersitial - caused by acute obstructive hydrocephalus (basically CSF going into the parenchyma. Primarily WHITE MATTER affected (increased diffusion on MR) - ACCENTUATED gray white differentiation