To present a case of central nervous system vasculitis presenting with butterfly shaped pattern mimicking central nervous system neoplasm. 

Central nervous system vasculitis is a rare and underdiagnosed disorder. It may mimic many disorders, like central nervous system tumors. Butterfly shaped pattern are usually associated with glioblastoma multiforme or central nervous system lymphoma. 

CASE REPORT

A 53 years old male patient presented  with headache for few weeks.  His neurological examination was unremarkable. During investigation, a MRI was performed. An intra-axial expansive lesion showing hypersignal on T2/FLAIR with epicenter in the splenium of the corpus callosum and extension to the adjacent periventricular white matter led to the hypothesis of a central nervous system neoplasm.  The lesion showed no contrast enhancement and normal diffusion sequences.  The CSF analysis showed only a mild proteinorrhaquia, with negative screening for infection and neoplasms. A biopsy was performed for diagnosis.  It showed a mononuclear infiltrate with vasculitis and vasogenic edema and the presence of TCD3 lymphocytes and foci of demyelination, suggestive initially of CLIPPERS/SLIPPERS. He was treated with metilprednisolone 1 gram for 5 days. A new MRI was performed after one month, that showed progression of the disorder.  For this reason, we decided to associate cyclophosphamide to the pulsotherapy.  Even with the association, the lesion was not improving after one month. Due to the initial treatment failure and atypical images for CLIPPERS, we performed a new biopsy, which showed diffuse demyelination, with marked macrophage activity, suggestive of central nervous system vasculitis. 

CNS vasculitis is a rare disorder and requires a high suspicion, even with investigation showing atypical lesion patterns.