Imaging of Intracranial Hemorrhage

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09/03/2008 18:15:00

Imaging of Intracranial Hemorrhage

Brandon A. Zielinski, MD, PhD

5 distinct stages

Hyperacute (< 12 hr)

Acute (12 hr -48 hr)

EARLY Subacute (2-7 days)

LATE Subacute (8 -30 days)

Chronic (months – years)

-based on blood breakdown products

-time-dependent changes in the hematoma are based on Hct, pH, O2


- CT beam density based on Hct, extent of blood retraction, and Hgb


- MRI signal characteristics determined by paramagnetic effects of

blood breakdown products, oxidation state of Fe, field strength, pulse sequence

Hyperacute stage (<12 hr)

- LIQUID blood initially

- 99% intracellular (RBC) OXYGENATED Hgb

- over first few hours, clot forms (RBC, PLT, serum, protein)

- MINIMAL reactive vasogenic edema

- serum extrusion increases Hgb concentration

- oxygenated Hgb has NO unpaired electrons and thus is diamagnetic

CT: hyperdense (high hgb)

T1: isointense (or hyperintense)

T2: hyperintense

(FLAIR: same as T2)

GRE (highly sensitive to susceptibility effects of para/superpara breakdown products): isointense core surrounded by hypointense rim

*in severe anemia, hyperacute/acute bleed ‘not as dense as expected’ on CT

Acute stage (12 – 48 hr)

- intracellular Hgb becomes DEOXYGENATED

- deoxyHgb has few unpaired electrons, and is paramagnetic

- vasogenic edema increases

CT: hyperdense

T1: isointense (hypointense)

T2: hypointense

GRE: diffusely hypointense


Early Subacute stage (2-7 days)

- conversion of denatured, deoxygenated Hgb into MET-Hgb

- vasogenic edema peaks

- MET-Hgb in intracellular compartment produces gradient between

intracell and extracell spaces

CT: slightly hyperdense

T1: hyperintense

T2: hypointense

GRE: diffusely hypointense

Late Subacute stage (8-30 days)

- lysis of RBC, release of MET-Hgb into extracellular space

- proteolysis of Hgb -> lower Hgb concentration

- vasogenic edema subsides

- MET-Hgb released into extracell space causes cancellation of gradient

across mebmrane

CT: becomes isodense (lower Hgb)

T1: hyperintense

T2: hyperintense

GRE: diffusely hypointense

(late subacute)

Chronic Stage (months – years)

- influx of macrophages, microglia, and astrocytes

- phagocytosis of MET-Hgb, conversion to hemosiderin and ferritin

- eventual resolution of hematoma and resultant fluid-filled cyst or


- Hemosiderin has many unpaired electrons (and thus is


CT: hypodense (resolution of hematoma)

T1: hypointense

T2: hypointense

GRE: hyperintense (or iso) core with hypointense rim

Special situations:


- old, “clinically silent”

- less than 5-10 mm, NOT seen on CT

- seen in up to 80% of pts with ICH, 25% of pts with stroke, 5% of

asx healthy individuals

- GRE signal is sensitive to hemodiserin-labeled macrophages in

perivascular space, indicative of previous extravasation of blood

- common risk factors are HTN, cerebral amyloid angiopathy, age

- case reports have suggested that people with microbleeds might be

at greater risk of hemorrhage after tPA, although larger studies dispute this

In one study, total number of microbleeds predicted risk of future ICH, and rate of accumulation predicted cognitive decline and poor functional outcome (thus number and rate of accumulation of microbleeds may be predictive factors for ICH and outcome, esp in HTN)


- CT negative 10% of the time, esp if >12 hours

- RBC mixing with high-O2-tension CSF delays generation of deoxyHgb, thus

T1/T2 signal change is delayed.

- FLAIR enhances conspicuity of hemorrhage, so can be used acutely.

- FLAIR may become standard for SAH, although at present LP still needed if



- CT studies suggest that extent of hypoattenuation at baseline can predict hemorrhagic transformation

- DWI studies: “large” DWI lesions and “low” ADC correlates with hemorrhagic transformation

Hemorrhagic transformation


Current Trends

Subacute left thalamic intracerebral haemorrhage (black arrow), chronic haematoma with slit-like appearance (white arrow), and large microbleed (green arrow), all seen with GRE MRI.

MRI can better identify and characterize underlying lesions, diffuse axonal injury, tumor characteristics, and GRE has been shown to be as sensitive to CT for detecting hyperacute blood

Near Future:

Pittsburgh Compound B labels amyloid deposits, ad has been used to detect CAA in people with suspected CAA-related ICH

NIS (mear-Infrared Spectroscopy): may becoe used in the field or at the bedside for rapid detection of epi/subdural bleeds

DWI, Perfusion MRI, DTI are coming…

52 YO admitted for acute onset R hemiparesis


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