CNS small vessel vasculitis: Distinct MRI features and histopathological correlation.

Abstract

Central nervous system (CNS) vasculitis is an uncommon disease, which is a diagnostic and therapeutic challenge for physicians. Large and medium vessel vasculitis is relatively easy to diagnose by angiogram compared to small vessel vasculitis, where angiograms are often normal; imaging features described till date are sensitive but not specific. Here, we describe distinct magnetic resonance (MR) imaging features of CNS small vessel vasculitis. Five histologically proven small vessel vasculitis cases were retrospectively reviewed from medical records between January 2008 to July 2012. Angiogram (magnetic resonance angiography in all and digital subtraction angiography in three patients) were normal, ruling out associated large and medium vessel vasculitis. The MR imaging findings were analyzed for T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities and blooming on susceptibility weighted imaging (SWI). Five patients (3 males) with a mean age of 34.2 years (range: 18 to 62 years) were included for analysis. Three patients with lymphocytic vasculitis had 43 discrete T2/FLAIR hyperintense lesions in brain parenchyma. All the brain lesions revealed central areas of SWI blooming in linear and/or lace-like pattern, surrounded by FLAIR hyperintensity. Corresponding T1-weighted contrast-enhanced images revealed subtle linear and lace-like enhancement. Coarse granular pattern of SWI blooming was seen in the patient with tuberculous vasculitis and no parenchymal abnormalities were seen in the patient with hypertrophic pachymeningitis. The linear SWI blooming along the course of small cerebral vessels and lace-like enhancement pattern in spin echo post-contrast T1-weighted sequences are suggestive MR imaging features for lymphocytic CNS small vessel vasculitis.