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Neuroradiology Case of the Week

Case 267

Brian Sorensen, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is an 81-year-old male presenting with mental status change.

Imaging Findings: Contiguous axial tomographic sections were obtained from the skull base to the vertex without intravenous contrast.

Diagnosis: Severe intracranial atherosclerosis

Discussion: Atherosclerosis is the most common cause of mortality and morbidity in the United States. Stroke, as the third leading cause of death and the most common cause of permanent disability, is a direct effect of atherosclerotic thromboembolism 30% of the time. Although extracranial carotid arterial plaque is a more common site of origin for thromboembolism, intracranial atherosclerotic disease accounts for as high as 10% of all ischemic strokes. Furthermore, according to the Warfarin-Aspirin Symptomatic Intracranial Disease study, patients with symptomatic intracranial atherosclerosis have a 13-14% risk of ipsilateral stroke at 1.8 years.
     Intracranial atherosclerosis has a number of important imaging features. Arterial bifurcations are commonly involved, particularly of the internal carotid and basilar artery. Less common sites include the Circle of Willis and middle cerebral arteries. MCA disease, although rare, possesses a high stroke death risk. Distal arteriolar involvement with multiple stenoses may mimic vasculitis.
     Atherosclerosis is most commonly identified on nonenhanced CT by mural calcification. T1- and T2-weighted MR images reveal flow void abnormality, which should not be confused with slow flow due to upstream stenosis or dissection. An intravascular hyperintense "dot" sign on FLAIR images may be seen with both slow flow and occlusion. CTA and MRA are excellent screening modalities. However, several caveats exist with MRA: (1) the contralateral vessel must be normal in caliber and (2) spin saturation may overestimate stenosis on 3D TOF. Although the combination of MRA and CTA approach a sensitivity and specificity close to digital subtraction angiography, DSA remains the gold standard for evaluating atherosclerotic stenosis. In addition to identifying focal stenosis, thrombosis, and occlusion, DSA is useful in the assessment of collateral status, plaque ulceration, and potential intervention (angioplasty vs. stent).

References:

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