Primary central nervous system vasculitis (PCNSV) is a rare inflammatory disease causing significant morbidity and mortality. We present a detailed history and clinical course of a patient with PCNSV along with a literature review. A 50-year-old Chinese female presented with a 6-month history of mild to moderate headache and sudden onset of visual loss. Early computed tomography of the brain showed multifocal infarctions. Over 3 weeks after admission, her clinical presentations changed considerably and her condition deteriorated. She became confused then fell in to semicoma, and developed left-sided paralysis and quadriparesis. At about 7 months after her illness, a magnetic resonance imaging of the brain revealed a tumour-like mass lesion within the right parietal lobe resulting in compressed posterior horn of the right lateral ventricle. In the end, a brain biopsy identified extensive vessel inflammation, which established the diagnosis of PCNSV. Steroid and immunosuppressive therapy dramatically improved the patient's condition. Our report highlights the importance of considering PCNSV as a differential diagnosis in patients who are suspected with encephalitis, multiple sclerosis, cerebral haemorrhage, cerebral thrombus, leukoencephalopathy, or brain tumour, etc. while their clinical presentations are exceptionally so changeable. This case also gives emphasis to the value of a brain biopsy in consolidating the diagnosis, and the efficacy of steroid and immunosuppressive therapy in PCNSV.