<prompt> Epidural hematoma on CT scan shows -Crescent shaped hyperdense lesionBiconvex hyperdense lesionBiconcave hyperdense lesionCrescent shaped hypodense lesion  <response>: Ans. is b i.e., Biconvex hyperdense lesion o Biconvex lens shaped or lenticular hyperdense23rd or mixed density lesionl3rd- Epidural hematomao Crescent concao-convex hyperdense 2 weeks or isodense 2-4 weeks or hypodense 4 weeeks lesion - subdural hematomao Intracranial hematoma may be: -1 Epidural hematoma Most common cause is injury to middle meningeal artery. Radiologically it appears as:-i Biconvex lens shaped or lenticularii In Acute cases - Hyperdense 23 or mixed density 13.iii In chronic cases - Hypodense2 Subdural hematoma ost common cause is stretching and tearing of cortical bridging veins. Radiologically it appears as : -i Crescent Concavo-convexii Hyperdense in acute 2 weeksiii Isodense in subacute 2-4 weeksiv Hypodense in chronic 4 weeks3 Subarachnoid hemorrhage Most common cause is rupture of berry saccular aneurysm. Investigation of choice for acute subarachnoid hemorrhage is non contrast CT. Blood in CSF on lumbar puncture is the hallmark of subarachnoid hemorrhage. If CT scan fails to diagnose SAH and there is high index of suspicion, lumber puncture is the next investigation. Investigation of choice for chronic SAH is MRL Investigation of choice for determining the etiology of SAH is four vessels both carotid and both vertebral digital substraction angiography. 