Brain hemorrhage Flashcards
(20 cards)
What factors dictate the appearance of hemorrhage on MRI?
Factors include:
* Age of hemorrhage
* Magnetic field strength and pulse sequence
* Biological factors (local pH, arterial vs. venous origin, BBB integrity, oxygen tension)
* Magnetic properties of iron over time
The degradation of hemoglobin influences the MRI characteristics of hemorrhage.
What is the MRI appearance of hyperacute hemorrhage?
T1 isointense; T2 hyperintense; T2* markedly hypointense rim; DWI hyperintense; ADC hypointense to intermediate
Hyperacute hemorrhage is characterized by the presence of oxyhemoglobin.
What happens to hemoglobin during the transition from hyperacute to acute hemorrhage?
Oxyhemoglobin is converted to deoxyhemoglobin, which is still intracellular and paramagnetic.
This transition occurs within hours to days.
What is the MRI appearance of acute hemorrhage?
T1 isointense; T2 hypointense; DWI hypointense; ADC hypointense
Acute hemorrhage occurs within hours to days after the initial bleed.
What defines early subacute hemorrhage on MRI?
Methemoglobin is present; T1 hyperintense; T2 hypointense; DWI hypointense; ADC hypointense
Early subacute hemorrhage is observed within the first few days.
What is the MRI appearance of late subacute to early chronic hemorrhage?
Methemoglobin is extracellular; T1 hyperintense; T2 hyperintense; DWI hyperintense; ADC hypointense to intermediate
This stage occurs days to months after the hemorrhage.
What characterizes chronic hemorrhage on MRI?
Ferritin and hemosiderin are present; T1 hypointense; T2 hypointense; DWI hypointense center; ADC variable
Chronic hemorrhage can persist for days to indefinitely.
List differentials for T1 hyperintensity.
- Melanin
- Flow artifact
- Lipid
- Protein
- Manganese, iron, gadolinium, copper
- Calcification
- Vasopressin
These factors can mimic or obscure hemorrhage on MRI.
List differentials for T2 hypointensity.
- Gas
- Calcification
- Flow effects
- Protein
- High cellularity
- Iron or copper deposition
- Secretory granules in pituitary adenomas
Understanding these differentials is crucial for accurate diagnosis.
What are primary causes of intracranial hemorrhage?
- Hypertension
- Ceroid amyloid angiopathy
These causes are often seen in various patient populations.
What are secondary causes of intracranial hemorrhage?
- Neoplasia
- Thromboses
- Infectious/parasitic disease
- Trauma
- Arteriovenous malformations
- Cerebral cavernous malformations
- Aneurysms
- Coagulopathy
Secondary causes often relate to underlying conditions.
What is the characteristic appearance of focal intraparenchymal hemorrhage?
Mass lesion, often rounded/globular; variable perilesional edema; usually absence of contrast enhancement in acute stage
Focal intraparenchymal hemorrhage can have a cystic component.
What distinguishes neoplastic hemorrhage on MRI?
Irregular or incomplete hemosiderin rim; marked signal heterogeneity; persistent perilesional edema
This type of hemorrhage is associated with neoplasms.
What defines multifocal intraparenchymal hemorrhage?
Multifocal non-traumatic large hemorrhages, usually >5mm in size; associated with secondary metastatic neoplasia or coagulopathy
This condition can indicate significant underlying pathology.
What are cerebral microbleeds?
Small round/ovoid signal voids; associated blooming on T2*; absence of T1 and T2 hyperintensity
They are markers of underlying vascular pathology.
What characterizes subarachnoid hemorrhage on MRI?
Focal or diffuse hemorrhage confined to the subarachnoid space; serpentine or linear in shape; may displace cortical gray matter
This type of hemorrhage often comes from surface vessels.
What is the MRI finding for subdural hemorrhage?
Single or multiple crescent-shaped hemorrhages superficial to the brain; significant mass effect
Subdural hemorrhages are usually due to venous bleeding.
What are the MRI findings for epidural hemorrhage?
Most commonly convex or biconvex; may cross dural folds but not suture lines
Epidural hemorrhages are typically arterial in origin.
What defines intraventricular hemorrhage on MRI?
T2* signal void with susceptibility artifact; often bilateral; large clots may appear as solid intraventricular masses
This type of hemorrhage commonly arises from subependymal veins.
What miscellaneous causes can lead to microscopic hemorrhage?
Thiamine deficiency; hypoxia
These conditions can predispose to small hemorrhages.
