Finding-the-Path: MRI and MRA of the brain

Magnetic resonance imaging

Magnetic resonance angiography

Magnetic resonance (MR) imaging and MR angiography of the brain were performed two days later to evaluate the cerebral vessels and exclude hemorrhagic infarction. MRI confirms a large territorial infarct in the right MCA distribution with mild mass effect on the right lateral ventricle (arrow). The MR angiogram demonstrates diminished caliber and signal intensity of the right MCA and its distal branches (arrow).

Discussion

Stroke is a major cause of disability among adult Americans and the third leading cause of death after cardiac disease and cancer. Atherosclerosis is the principal cause of cerebral thromboembolism in over 90% of cases. Although stroke is a clinical diagnosis, this diagnosis is incorrect in approximately 10% of patients admitted for stroke. The role of head CT in the management of acute cerebral infarction is to exclude an intracranial hemorrhage or a structural lesion such as a vascular malformation or a tumor that can mimic stroke clinically. Although head CT scans obtained within the first few hours after stroke are normal in 60% of patients, several early signs can be seen in strokes less than 6 hours old. These signs include increased attenuation in the middle cerebral artery (dense MCA sign), loss of gray-white junction along the insula (insular ribbon sign), obscuration of the lentiform nucleus, and effacement of the sulci along the cortex. When the initial CT scan is normal, a repeat scan in 48 hours will, in about 80% of patients, show the infarct as an area of decreased attenuation with mass effect on the adjacent structures. MRI is more sensitive than CT in identifying and localizing acute cerebral infarcts. Vascular flow related abnormalities can be seen on contrast-enhanced MRI within minutes of symptom onset. However, standard MRI sequences fail to detect acute infarct in 10-20% of patients. MRI/MRA are often helpful as follow-up studies to evaluate the extent of infarction, presence or absence of hemorrhage, and degree of stenosis of the cerebral vessels. In patients with persistent transient ischemic attacks, the combination of carotid vascular ultrasonography and MR angiography may obviate the need for carotid angiography.

Contact the BrighamRAD Design Team for additional information about this site.