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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues
- Clinical history major determinant of DDx (if available) - Arteriosclerotic vascular disease(ASVD): Clinical history of uncontrolled diabetes, hypertension, hyperlipidemia, smoking - Reversible cerebral vasoconstriction syndrome(RCVS): Thunderclap headache and vasoactive drug use (cannabis, SSRI) - Vasospasm: Recent subarachnoid hemorrhage (SAH) - Vasculitis: Smoldering headache and CSF/systemic inflammatory markers - Intravascular large B-cell lymphoma (IVL): DDx excluded, progression despite treatment
- Effect of patient age on DDx - Middle-aged or older adults - ASVD, vasculitis, RCVS - Child or young adult - Transient arteriopathy of young, moyamoya, inherited vasculopathy (e.g., Ehlers-Danlos), congenital infection (e.g., HIV vasculopathy)
- Is there hemorrhage? - Subarachnoid→ RCVS, vasospasm, dissection, or pseudoaneurysm - Parenchymal→ vasculitis, RCVS, moyamoya, IVL
Helpful Clues for Common Diagnoses
- Atherosclerosis**, Intracranial** - Location - ASVD occurs in areas of flow reversal and oscillatory shear stress (e.g., bifurcations) - Proximal circle of Willis branches, vertebrobasilar, internal carotid arteries (ICAs) - Lumen imaging of intracranial atherosclerosis - Focal stenoses, lumen irregularities, elongation/ectasia - Stenosis measured by WASID criteria - CTA vs. 3D time-of-flight (TOF) MRA - CTA has slightly higher resolution than 3D TOF - 3D TOF can be limited in tortuous vessels with signal loss in inferiorly directed branches - 3D TOF MRA at 3T outperforms CTA in distal branches due to venous contamination - 3D TOF MIPs outperform CTA MIPs - MR + CT - High T2 signal → lipid/necrotic core (ASVD) - High T1 signal → intraplaque hemorrhage (less common) - Enhancement → unstable/active ASVD - Highly associated with acute territorial stroke; can persist for months - High repeat stroke risk despite medical therapy (15-30% per year) - Positive remodeling → outward bulging of vessel wall as compensatory response to plaque; may have little vessel narrowing on angiographic imaging - Calcification on CT/CTA → atherosclerosis - Most common cause of vessel narrowing ASVD, notvasculitis
Helpful Clues for Less Common Diagnoses
- Reversible Cerebral Vasoconstriction Syndrome - Etiology - Spontaneous, related to vasoactive substances, postpartum state - Lumen imaging - Multifocal segmental narrowing, ± dilatations - Vessel wall imaging - No T2 signal, no or mild enhancement
- Vasospasm - Etiology - Most common: Aneurysmal SAH - Less common: Trauma - Lumen imaging - Multifocal narrowing - Vessel wall imaging - No T2 signal, no or mild enhancement
- Vasculitis - Etiology - Primary arteritis of CNS - Secondary vasculitis - Infectious - Autoimmune - Lumen imaging - Multifocal alternating stenoses, dilatations - Vessel wall imaging - T2 signal: None or mild - Wall enhancement: Positive, concentric
- Vasculopathy, Non-ASVD - Lumen imaging - Fusiform or alternating areas of stenosis and dilatation, "beading" - Long, nonbranching vessel segments - Vessel wall imaging - Not well studied, likely active and inactive stages similar to ASVD - Younger patients - Vertebrobasilar > carotid - Inherited (e.g., Ehlers-Danlos) or acquired (e.g., viral)
- Dissection - Pathophysiology - Can be traumatic or spontaneous, ± SAH - Often combined with pseudoaneurysm (dissecting pseudoaneurysm) - Location - Vertebral > > ICA - Lumen imaging - Lumen irregularity, ± dilation (pseudoaneurysm) - Reimage if dilation, risk of growth/rupture - Vessel wall imaging - T2 signal: Variable high signal, depends on age - T1 signal: High signal if subacute (~ 2-8 weeks old) - Wall enhancement: Avid if acute
- Pseudoaneurysm - Pathophysiology - Lacks normal arterial wall layers, contained by adventitia or cavitated clot - Trauma, infection = common causes - Rapidly changes within hours or days, easily ruptures - Location - Can be peripheral location (distal to circle of Willis) - Often adjacent to skull base fractures or dura - e.g., dorsal variant ICA blister aneurysm - Lumen imaging - Often adjacent vessel segment irregular - Suspect pseudoaneurysm if broad-based bulge without neck - Look carefully for pseudoaneurysms in "angiogram-negative" SAH
Helpful Clues for Rare Diagnoses
- Intravascular Large B-Cell Lymphoma - Consider after excluding other diagnoses - Often initial response with steroids with recrudescence of symptoms and progression of infarcts and hemorrhages
- Moyamoya - Characteristic "puff of smoke" on DSA - Most often seen in children and young adults
- Radiation Vasculopathy - Consider radiation vasculopathy if age-accelerated vessel narrowing/ASVD - History of prior radiation key
Other Essential Information
- Clinical management of intracranial atherosclerosis - SAMPRIS trial: Intensive medical therapy superior to stenting - Recommended by SAMPRIS for symptomatic intracranial ASVD - Life coach, smoking cessation, dual antiplatelets, antihypertensive therapy, statins - Still had ~ 15% annual stroke risk
- Artifacts and limitations - Motion degrades CTA, MRA, and vessel wall MR - Motion affects studies with longer acquisition times: Vessel wall MR > MRA > CTA - Motion degrades black blood vessel wall MR due to misregistration artifact ("ghosting" can mimic wall enhancement) - Pulsation artifact - Can obscure vessel narrowing on 3D TOF - Occurs in phase-encoding direction - Occluded vessels difficult to detect on CTA/MRA - T2 MR to troubleshoot (e.g., T2 SPACE) - CSF pulsation artifact may cause spin dephasing and mimic pathology (especially around distal basilar artery) - DANTE prepulse eliminates CSF pulsation artifact - Incomplete suppression of flowing contrast in black blood imaging - DANTE prepulse eliminates flowing contrast - DANTE T1 SPACE much higher signal:noise ratio and contrast:noise ratio than T1 SPACE alone - Slow-flow and entry slice phenomenon → T1 shortening may mimic thrombus - Venous contrast on CTA limits distal branch evaluation (3rd and 4th order) - 3D TOF MRA at 3T outperforms CTA in these areas

References

Selected References

Images

Selected Images

Atherosclerosis, Intracranial MIP MRA shows multifocal stenoses , characteristic for intracranial atherosclerosis, the most common cause of alternating stenoses and dilatations. Risk factors include diabetes, hypertension, hyperlipidemia, and smoking.

Atherosclerosis, Intracranial CTA in the right middle cerebral artery (MCA) shows focal severe stenosis with associated avid enhancement on postcontrast vessel wall MR as well as T2 hyperintensity in the vessel wall, consistent with active atherosclerotic plaque.

Reversible Cerebral Vasoconstriction Syndrome NECT in a patient with RCVS shows vertex subarachnoid hemorrhage (SAH) . There is no associated enhancement on MR T1 DANTE SPACE pre- or post- contrast. Typical presentation includes a thunderclap headache; history of vasoactive drug use is also common.

Reversible Cerebral Vasoconstriction Syndrome DSA in the same patient shows multifocal narrowing on the initial ICA injection. Following Verapamil injection, there is reversal of the multifocal narrowing with a more normal caliber of the intracranial vasculature, compatible with RCVS.

Vasospasm Lateral DSA shows a saccular aneurysm and narrowed cortical vessels , indicating a vasospasm caused by an aneurysmal SAH (aSAH).

Vasospasm DWI MR in a traumatic brain injury patient shows SAH and right MCA vasospasm with acute infarct . The right MCA proximal M2 is narrowed on 3D TOF MR . No intrinsic MR T1 signal is seen on precontrast image, and there is no enhancement on postcontrast DANTE T1 SPACE, consistent with posttraumatic SAH-induced vasospasm.

Vasculitis 3D TOF MRA in a young patient with vasculitis and MCA stroke shows lumen irregularity of the right anterior circulation . DSA confirms lumen findings and more subtle right M2 MCA narrowing . Avid wall enhancement is on DANTE T1 SPACE comparing pre- (magnified ), vs. postcontrast (magnified ).

Vasculopathy, Non-ASVD MIP MRA in a drug user shows multifocal narrowing in the right MCA and anterior cerebral artery branches , confirmed on DSA , compatible with drug-induced vasculopathy.

Dissection Axial T1 C+ FS MR in a patient with posterior circulation ischemic symptoms after severe deceleration injury shows both vertebral arteries markedly enlarged by subacute clot . The right vertebral artery is completely thrombosed, while small residual lumen is seen on the left .

Pseudoaneurysm Right V4 vertebral artery pseudoaneurysm in a trauma patient with initial and follow-up 3D TOF MRA shows growth with 2 areas of dilation , confirmed on angiography (DSA and 3D ).

Pseudoaneurysm Dorsal variant ICA pseudoaneurysm is shown on 3D TOF MRA and DSA with wall enhancement on MR T1 SPACE and magnified views in bottom right.

Intravascular Large B-Cell Lymphoma Biopsy-proven intravascular lymphoma with multifocal hemorrhages, infarcts, and surrounding edema is shown on FLAIR, DTI, and SWI. DSA shows multifocal distal vessel lumen irregularity . Vessel wall MR was negative. Intravascular large B-cell lymphoma is often a diagnosis of exclusion. Skin biopsy or brain biopsy is typically needed to make the diagnosis.

Moyamoya Lateral DSA angiography shows tapered occlusion of supraclinoid ICA with a tangle of "puff of smoke" lenticulostriate , characteristic of moyamoya.

Radiation Vasculopathy Axial DWI shows a recent infarct superimposed on a FLAIR hyperintense , remote right posterior cerebral artery (PCA) infarct with delayed MTT in a patient with radiation vasculopathy. DSA shows severe right PCA narrowing with near occlusion and contralateral PCA narrowing .

Additional Images

Vasculopathy, Non-ASVD Lateral angiography shows a posterior communicating ICA aneurysm with multiple lobulations and an unusually long "aspect ratio." This atypical aneurysm is likely related to a vasculopathy.

$Lateral angiography in a patient with a skull base fracture and stroke shows a pseudoaneurysm at the junction of the ascending/horizontal cavernous carotid artery. Note narrowing and intimal irregularity , a potential source for embolic stroke.$ Pseudoaneurysm Lateral angiography in a patient with a skull base fracture and stroke shows a pseudoaneurysm at the junction of the ascending/horizontal cavernous carotid artery. Note narrowing and intimal irregularity , a potential source for embolic stroke.

$Axial T2 MR in a 30-year-old man with headache, a history of a motor vehicle accident and basilar skull fracture 10 years earlier shows a cavernous pseudoaneurysm .$ Pseudoaneurysm Axial T2 MR in a 30-year-old man with headache, a history of a motor vehicle accident and basilar skull fracture 10 years earlier shows a cavernous pseudoaneurysm .

Pseudoaneurysm Anteroposterior angiography in a patient who decompensated clinically 24 hours after admission for a closed head injury shows traumatic pseudoaneurysm caused by impingement of ACA against falx.

Atherosclerosis, Intracranial 3D TOF MPR and axial TOF show ~ 50% narrowing of the left V4 vertebral artery. T2 SPACE shows a lipid/necrotic core . MPRAGE is positive for IPH . DANTE T1 SPACE pre- and post- contrast images demonstrate avid wall enhancement (active plaque).

Vasculopathy, Non-ASVD HIV vasculopathy with bilateral fusiform aneurysms of the terminal ICAs is shown. A T2-hyperintense clot is present in the right ICA terminus aneurysm , and there is a preserved flow void in the aneurysmal left ICA terminus . CTA shows an occluded right terminal ICA aneurysm and patent left terminal ICA fusiform aneurysm . DSA confirms these findings with a fusiform aneurysm of the left ICA terminus .

Reversible Cerebral Vasoconstriction Syndrome Postpartum RCVS shows slow flow/vertex SAH on FLAIR , multivessel narrowing on 3D TOF , and absent enhancement on DANTE T1 SPACE pre- or post- contrast.

Atherosclerosis, Intracranial Anteroposterior angiography shows multifocal stenoses characteristic for atherosclerosis, the most common cause of alternating stenoses and dilatations.

Atherosclerosis, Intracranial DSA shows multifocal stenoses characteristic for atherosclerosis, the most common cause of alternating stenoses and dilatations.

Vasculopathy, Non-ASVD DSA shows fusiform elongation of an MCA branch . The patient later admitted to using street drugs.

Pseudoaneurysm Lateral angiography shows a classic blood, blister-like aneurysm along the greater curvature of the supraclinoid ICA. A hemispherical bulge with a broad orifice is typical for blood blister aneurysms. (Courtesy D. Phillips, MD).

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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Helpful Clues for Common Diagnoses

Helpful Clues for Less Common Diagnoses

Helpful Clues for Rare Diagnoses

Other Essential Information