Primary Arteritis of the CNS

KEY FACTS

TERMINOLOGY

• Primary arteritis of CNS (PACNS)

○ No evidence of secondary (systemic) vasculitis

○ May involve intracranial arteries of any size

• 2 features essential for histopathologic diagnosis

○ Inflammation and necrosis of blood vessel wall

IMAGING

• CT

○ Look for secondary signs of vasculitis (ischemia,

infarction)

○ Hypodensities on CT

○ Especially basal ganglia, subcortical white matter

• MR (high resolution)

○ Multifocal punctate, linear hyperintensities on T2/FLAIR

○ Vessel wall imaging with thin-section, high-resolution

(3T) T1 C+

– Circumferential, smooth, long segment

○ ± patchy parenchymal enhancement, restricted diffusion

○ DWI variable (may restrict)

• DSA

○ Once considered imaging gold standard

○ "Beaded" arteries (irregular stenoses, dilatations) on DSA

– Peripheral branches > proximal (circle of Willis)

○ Less common: Long-segment stenoses,

pseudoaneurysms, occlusions

PATHOLOGY

• Brain biopsy may be required to confirm diagnosis

○ 75-80% sensitive

○ Negative biopsy does not exclude PACNS

CLINICAL ISSUES

• Wide age range (mean: 42 years)

DIAGNOSTIC CHECKLIST

• Atherosclerosis is by far most common cause of vasculitislike DSA pattern in older adults, not PACNS

(Left) Graphic depicts primary

arteritis of the CNS with areas

of narrowing ﬈ and

dilatation ﬊ of the middle

cerebral artery branches, as

well as foci of patchy ischemia

and microbleeds ﬉ in the

basal ganglia, cortex, and

subcortical white matter.

(Right) T1 C+ FS scan in a 62-

year-old man with ataxia,

diplopia, and confusion shows

innumerable abnormal linear

﬇ and dot-like areas of

enhancement ﬈ in the

subcortical and deep white

matter of both hemispheres.

This is biopsy-proven primary

arteritis of the CNS (PACNS).

(Left) Lateral DSA in a 34-

year-old woman with multiple

strokes shows markedly

irregular posterior cerebral

artery ﬈ with alternating

areas of stenosis and

dilatation. (Right) Thin-section

T1 C+ FS in the same patient

shows enhancement in the

wall of the left posterior

cerebral artery ﬈. Wall

enhancement can occur in

both vasculitis and

atherosclerosis with chronic

inflammation. Patient was a

smoker with cardiovascular

risk factors, but young age and

clinical features were most

consistent with PACNS.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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