Acute SDH is seen on CT scan as:

Ans. c (Crescent-shaped hyperdense lesion). (Ref. Annie Osborn's Diagnostic Neuroradiology, 205).A Crescent-shaped or concavoconvex collection is SDH. Hyperdense on CT are fresh bleeds.Extradural hematoma verse subdural hematomaFeaturesEDHSDHIncidence1-4% overall10-20% overallAsso fractureAssociated in 85-95% cases.Underlying may not be presentEtiologyLacerated middle meningeal artery/ dural sinusStretching, tearing of bridging in 70 to 85% cases and venous "OOZE" or MMA cortical veins tear without in 15% cases onlyLocationBetween skull and dura.Between dura and arachnoid.Crosses dural attachments but not sutures.ImagingCT: Biconvex /LentiformAcute are hyperdense on CT.Chronic are hypodense on CT.CT: . Concavo-convex/ Crescentic.Acute are hyperdense on CT. Chronic are hypodense on CT.