Imaging Ischmic And Hemorrhagic Stroke (CT And DWI) Flashcards
Objectives
Indicate the imagining modality that was used to produce the image
What is the name of the lesion
Describe the location of the lesion
Describe the radiological appearance of the lesion
What is the usual cause of the lesion
What are the clinical features of the lesion
CT Early Signs of Ischemia
Hypoattenuating brain tissue Obscuration of the lentiform nucleus Dense MCA (middle cerebral artery) sign "Insular ribbon" Sign Sulcal effacement
Hypoattenuation of Brain Tissue
On CT: is highly specific for irreversible ischemic brain damage if it’s detected within first 6 hours.
Patients who present with symptoms of stoke and who demonstrate hypodensity on CT within the first 6 hours were proven to have larger infarct volumes, more severe symptoms, less favorable clinical courses and they even have a higher risk of hemorrhage
Therefore whenever you see hypodensity in a patient with stroke this means bad news. No hypodensity on CT is a good sign
Why Do we see Ischemia on CT as Hypoattenuation Brian Tissue?
Cytotoxic edema develops as a result of failure of the ion-pumps. These fail due to an inadequate supply of ATP
Example: see hypoattenuating brain tissue in the right hemisphere. Dx is infection because of the location (vascular territory of the MCA) and because of the involvement of gray and white matter, which is also very typical for infarction
Obscuration of the Lentiform Nucleus
Putamen and Globus Pallidus make up lentiform nucleus
Obscuration of the lentiform nucleus, also called “blurred basal ganglia” is an important signal of infarction
It’s seen in middle cerebral artery infarction and is one of the earliest and most frequently seen signs
The basal ganglia are almost always involved in MCA-infarction
In the image, Emergent CT revealed loss of normal left lentiform nuclear attenuation consistent with cytotoxic edema, as compared with the normal appearing right lentiform nucleus
Insular Ribbon Sign
Refers to hypodensity and swelling of the insular cortex. It’s a very indicative and subtle early CT-sign of infection in the territory of the MCA. This region is very sensitive to Ischemia because it’s the furthest removed from collateral flow
Dense MCA (Middle cerebral artery) sign
Due to acute occlusion and swelling in the MCA
This is a result of thrombus or embolus in the MCA. On the left a patient with a dense MCA sign.
On CT-angiography occlusion of the MCA is visible
Sulcal Effacement
You can’t see the sulci
Appearance of Blood on CT
ACUTE (less than a week): clot retraction and loss of water result in high attenuation of the x-ray beam (bright appearance)
Subacute (up to several weeks): over days to weeks there’s a gradual decrease in attenuation and eventually the blood becomes isodense with brain (looks like brain-gray appearance)
Chronic (more than several weeks): with additional time there’s further decrease in attenuation, becoming lower (hypodense) than that of the brain parenchyma-dark appearance
Epidural Hematoma
Location: in the tight potential space between the dura and the skull
Usual cause: rupture of the middle meningeal artery due to fracture of the temporal bone by head trauma (area of the pterion is weak)
Clinical features and radiological appearance: rapidly expanding hemorrhage under Arterial pressure peels the dura away from the inner surface of the skull forming a lens-shaped biconvex hematoma that often doesn’t spread past the cranial sutures where the dura is tightly AP posed to the skull
Initially patient may have no symptoms (lucid interval). However, within a few hours the hematoma begins to compress brain tissue, often causing elevated ICP and ultimately herniation and death unless treated surgically
Subdural Hematoma
Location: in the potential space between the dura and loosely adherent arachnoid mater
Usual cause: rupture of bridging veins, which are particularly vulnerable to shear injury as they cross the arachnoid into the dura (on their way to the superior sagittal sinus)
Clinical features and radiological appearance: Venous blood dissects relatively easily between the dura and the arachnoid, spreading out over a large area and forming a crescent-shaped hematoma. Types-chronic, acute and subacute
Acute Subdural Hematoma (on CT)
Fresh blood undergoes clot retraction, attenuated x-rays and gives a bright signal
Subacute Subdural Hematoma (CT)
The blood has the same attenuation as that of the adjacent gray matter and is difficult to distinguish. Note that the gray matter-white matter junction is displaced medially, and midline shift is seen, indicating the presence of a space-occupying extra-axial lesion
Chronic Subdural Hematoma (CT)
Often seen in the elderly where atrophy allows the brain to move more freely within the cranial vault, thus making the bridging veins more susceptible to shear injury. This type of hematoma may be seen with minimal or no known history of trauma.
Oozing slow, venous blood collects over weeks to months, allowing the brain to accommodate and there causing vague symptoms such as headache, cognitive impairment and unsteady gait
Subarachnoid Hemorrhage
Location: In the CSF-filled space between the arachnoid and the pia, which contains the major blood vessels of the brain
Radiological appearance: unlike subdural hematoma, blood can be seen on CT to track down into sulci following the contours of the pia
Usual Cause: SAH is seen in 2 clinical settings: nontraumatic and traumatic
