Purpose:
We report four patients with central nervous system (CNS) vasculitis, in which vessel wall imaging (VWI) findings were instrumental in diagnosis and subsequent management. 

Materials and Methods:
Case 1: A 33-year-old male presented with cerebellar infarcts and vertebral dissections. Digital subtraction angiography (DSA) demonstrated no sign of vasculopathy. VWI revealed concentric thickening and enhancement of right posterior cerebral and left anterior choroidal arteries. Serum and CSF analysis revealed high titers of Human Herpesvirus type 6.
Case 2: A 56-year-old male with HSV1 encephalitis was treated and mental status improved. Surveillance neuroimaging, however, revealed ongoing pathology, including MCA territory distal hyperintense vessels. VWI revealed middle cerebral artery (MCA) concentric smooth contrast enhancement.
Case 3: A 41-year-old obese female with hypertension and tobacco use presented with recurrent transient ischemic attacks. Computed topography angiography demonstrated bilateral MCA stenosis. Patient refused DSA. VWI revealed uniform enhancement and thickening of the arterial wall. A calf rash biopsy diagnosed a mixed connective tissue disease. 
Case 4: A 41-year-old male presented with 1-week progressive headache & encephalopathy.  Brain MRI revealed scattered punctate cerebral infarctions in multiple vascular territories.  Embolic workup was unrevealing.  Subsequent MRI Brain with contrast 2 days after initial scan showed increase in number of punctate infarcts, but no abnormal contrast enhancement.  DSA was normal.  VWI showed diffuse enhancement of distal cerebral vasculature, prompting further infectious and rheumatologic investigations, immunotherapy consideration, and an expedited brain biopsy.  This patient was ultimately diagnosed with Susac syndrome, a rare autoimmune endotheliopathy.

Results:
In cases 1 and 2, VWI visualized vasculitic changes that were crucial to proper diagnoses of viral arteriopathies. In case 3, VWI findings led to a diagnosis of mixed connective tissue disease prompting immunotherapy in a patient with stenoocclusive disease that was initially attributed to atherosclerosis. In Case 4, recognition of distal vasculitic changes on VWI prompted accelerated brain biopsy for diagnostic confirmation of a rare automimmune endotheliopathy and immunotherapy initiation. In each case, VWI provided a noninvasive modality to track intracranial vasculopathy progression and response to treatment. 

Conclusions:
Etiological diagnosis of intracranial vasculopathies remains challenging. Whereas traditional angiographic modalities depict vessel lumen appearance, they provide very limited information regarding arterial wall integrity and pathology. Conversely, the underlying vasculitic process has typical imaging characteristics on VWI, as illustrated in our case-series. In order to provide targeted therapy, clinicians should take advantage of the nuanced information VWI provides.

Magnetic Resonance Vessel Wall Imaging in Central Nervous System Vasculitides: a Case-Series

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