From the Guidelines
Distinguishing between intracranial atherosclerosis and vasculitis on CTA requires evaluation of several key imaging features, with the most recent and highest quality study suggesting that vasculitis shows more diffuse, segmental, and often multifocal narrowing with a beaded appearance, as noted in the 2021 study by the American College of Radiology 1.
Key Imaging Features
- Atherosclerosis typically presents with focal, eccentric luminal narrowing, calcifications along vessel walls, and involvement of bifurcation points or proximal segments of major cerebral arteries.
- Vasculitis shows more diffuse, segmental, and often multifocal narrowing with a beaded appearance, vessel walls may demonstrate enhancement and thickening without calcification.
- Additional findings that suggest vasculitis include microaneurysms, vessel wall enhancement on contrast studies, and a lack of atherosclerotic risk factors in the patient's history.
Clinical Context
- Clinical context is crucial, as vasculitis often presents with systemic symptoms, elevated inflammatory markers, and a more acute onset compared to atherosclerosis.
- The 2021 guideline for the prevention of stroke in patients with stroke and transient ischemic attack also emphasizes the importance of identifying symptomatic intracranial atherosclerotic disease and differentiating it from vasculitis 1.
Additional Imaging
- When CTA findings are equivocal, additional imaging such as high-resolution vessel wall MRI with contrast can help differentiate between these conditions by showing characteristic enhancement patterns in vasculitis.
- In some cases, conventional angiography may be necessary for definitive diagnosis, particularly for smaller vessel involvement that may not be visible on CTA, as noted in the 2011 guideline on the management of patients with extracranial carotid and vertebral artery disease 1.
Limitations of CTA
- CTA can provide a noninvasive assessment of intracranial vessels in arteriopathies, but is typically negative in small-vessel vasculitis, as noted in the 2020 study on ACR appropriateness criteria for cerebrovascular disease in children 1.
- The 2020 study on ACR appropriateness criteria for cerebrovascular disease in children also highlights the importance of considering childhood primary angiitis of the central nervous system, a condition that can result in stroke and requires a combination of clinical, imaging, and histologic features for diagnosis 1.
From the Research
Distinguishing between Intracranial Atherosclerosis and Vasculitis using CTA
To distinguish between intracranial atherosclerosis and vasculitis using Computed Tomography Angiography (CTA), several factors need to be considered:
- The ability of CTA to detect and quantify intracranial stenosis and occlusion compared to digital subtraction angiography (DSA) and magnetic resonance angiography (MRA) 2
- The sensitivity and positive predictive value of CTA for intracranial stenosis and occlusion, which have been shown to be higher than those of MRA 2
- The use of 3D high-resolution magnetic resonance imaging (3D HR-MRI) for diagnosing and evaluating stenosis in the entire circle of Willis, which has been compared to DSA 3
- The diagnostic accuracy, sensitivity, and positive predictive value of 3D HR-MRI for atherosclerosis, which have been shown to be better than those of DSA 3
Technical Aspects of VW-MRI
The technical aspects of vessel wall MRI (VW-MRI) that need to be considered include:
- Flow suppression, both in blood and cerebrospinal fluid (CSF) 4
- Spatial resolution and signal-to-noise ratio (SNR) 4
- The use of 3D high-resolution black blood sequences for intracranial vessel wall MRI (VW-MRI) 4
Clinical Applications of VW-MRI
VW-MRI has several clinical applications, including: