Specific Imaging Findings

Imaging features indicative of Central Nervous System Vasculitis (CNSV) are multiple infarcts of various ages in more than one vascular territory. CT images may be negative in the hyperacute phase and multifocal low-density lesions may be depicted in the acute–subacute phase. Localized subarachnoid hemorrhage is occasionally seen. On MRI, CNSV is characterized by scattered areas of high T2 and low T1 signal intensity in the deep gray matter, cortical and subcortical regions, which may be quite nonspecific. In the acute–subacute phase dark foci of cytotoxic edema are present on ADC maps. Increase in ADC values in the otherwise normal-appearing white matter may represent vasogenic edema, chronic destruction, and/or Wallerian degeneration. Microhemorrhages are frequently present on T2*-weighted images, subarachnoid blood is sometimes seen, usually along the cortical sulci. Scattered areas of leptomeningeal enhancement with underlying brain signal abnormalities are highly characteristic for vasculitis, but are seen in only about a third of cases. Wall thickening and enhancement of large intracranial vessels is a diagnostic sign of CNSV, present in most patients. Classic angiographic findings are diffuse segmental arterial wall narrowing and associated poststenotic dilation, referred to as “beading” or “string-of-beads”. Multi-vessel involvement increases the suspicion for CNSV. When more than two stenoses in at least two separate vascular distributions are depicted on MRA, DSA is not needed.

Pertinent Clinical Information

CNSV can affect any age group, but is more common in individuals 40–60 years old. Clinical manifestations are nonspecific, including headache, encephalopathy and, less frequently, focal neurological deficits. Diagnosis is often very difficult. Cerebral catheter angiography has been the standard for presumed vasculitis, with sensitivity in the range of about 80%, while MRA (and CTA) are slightly less sensitive. Cerebral ormeningeal biopsy is the gold standard but also has limited sensitivity. A combination of steroids, immunosuppressants, and immunomodulating agents is used for treatment.