Tumor-mimicking primary angiitis of the central nervous system: initial and follow-up MR features

Primary angiitis of the central nervous system (PACNS) is an extremely rare vasculitis of unknown etiology. The purpose of this study was to describe the initial and follow-up magnetic resonance (MR) imaging features of the tumor-mimicking PACNS.

We retrospectively reviewed a total of 21 initial and follow-up brain MR images obtained in four patients with biopsy-proven PACNS mimicking brain tumor on MR images during the periods from 1 to 8.1 years. In the initial study, diffusion-weighted imaging (DWI; n = 4), MR angiogram (n = 4), conventional catheter angiogram (n = 3), perfusion MR (n = 1), and computed tomography (n = 1) and proton MR spectroscopy (MRS; n = 2) were included. The lesions of the brain were qualitatively assessed in terms of location, number, size, shape, signal intensity, absence or presence of hemorrhage, enhancement pattern, and changes on the follow-up studies.

Initially, the lesion manifested as single suprasellar (n = 1) and frontal hemispheric (n = 1) mass and as multiple-enhancing lesions in the unilateral supratentorial hemisphere (n = 2). A patient showed steno-occlusive lesions in the internal carotid and middle cerebral arteries. DWI, perfusion imaging, and MRS revealed inconsistent findings among the patients. On the follow-up studies, a patient had two relapses but there was either significant decrease in size and extent or disappearance of the lesions with immunosuppressive therapy in all patients.

Tumor-mimicking PACNS shows variable features on initial MR images but shows good responses to appropriate immunosuppressive therapy on follow-up MR images.