Q: How you can differentiate acute Sub-Dural-Hematoma (SDH) from subacute or chronic SDHs on CT scan of head?


Answer: 

On CT scan of head, acute SDH appears as a high-density crescentic collection across the hemispheric convexity. 

In contrast, subacute and chronic SDH appears as isodense or hypodense crescent-shaped lesions  that deform the surface of the brain.