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• Acute hemorrhage will appear hyperdense (Bright white) on cranial CT images. This is attributed to the fact that globin is relatively dense and hence effectively absorbs xray beams.

• As the blood becomes older and globin molecules breaks down, it will lose this hyperdense appearance, beginning at the perphery.

• On CT scan, blood will become isodense with the brain at 1- 2 weeks, depending on clot size and will become hypodense with the brain at approximately 2 to 3 weeks.

EDH

• They appears as a lens-shaped (Biconvex collection) of blood, usually over the brain convexity.

• An EDH will not cross a suture line, as the dura is tacked down in these areas.

EDH : Note the biconvex hyperdense lesion over the temporopareital region been limited by suture lines suggestive of EDH.

SDH

• They appears as a sickle or crescent shaped collection of blood, usually over the cerebral convexity.

• In contrast to EDH, SDH crosses suture lines, as there is no anatomic limitation to blood flow below the dura.

• It can be either acute or chronic.

CT Brain plain shows acute SDH on the left side with midline shift and effacement of ventricles. Note the hyperdense lesion over the left side which concave in shape crossing the suture lines extending from frontopareital to occipital region.



Intraparenchymal Hemorrhage

• Cranial CT can reliably identify intraparenchymal hematomas as small as 5mm.

• These appears as high density areas on the CT scan.

• Traumatic intraparenchymal hemorrhages may be seen immediately following an injury, or they can appear in a delayed fashion. Traumatic contusions most commonly occur in areas where sudden deceleration of the head cases the brain to impact on bony prominences.

• Non traumatic hemorrhagic lesions due to hypertensive disease are typcaly seen in elderly patients and occur most frequently in the basal ganglia.

• Hemorrhage from such lesion may rupture into the ventricular space.

• Intraparenhymal bleeding can be caused by AV malformations, bleeding from or into a tumor, amyloid angiopathy or aneurysms that happen to rupture inot the substance of the brain.

SAH

• Subarachnoid hemorrhage is defined as hemorrhage into any subarachnoid space that is normally filled with CSF.

• The hyperdensity of blood in the subarachnoid space is visible within minutes of onset of hemorrhage. CT Scan is 95 – 9 8% sensitive to detect SAH. The sensitivity is reported to decrease as follows :

  • 90 – 95 % at 24 hours

  • 80% at 3 days

  • 50% at 1 week

  • 30% at 2 weeks



CT Brain plain showing SAH (Left side). Note the hyperdense (blood) filling the cisterns.                                                                Normal CT Brain Plain with CSF in the cisterns