Primary angiitis of the central nervous system (PACNS) is a rare vasculitis involving medium and small blood vessels of the brain, spinal cord, and meninges, without systemic involvement. The diffuse and patchy nature of its pathology is reflected by a wide spectrum of nonspecific clinical symptoms. Diagnosis is challenging due to lack of defined clinical criteria or specific imaging findings. Specific workup should be done only after exclusion of other etiologies, including infectious, neoplastic, toxic, and other vascular etiologies including systemic vasculitis. Given the fact that it is a patchy disease with 25% of the biopsies being falsely negative, treating physician should have a high index of suspicion despite negative initial neurovascular imaging and biopsy results. Once diagnosed, early treatment with immunosuppressive therapy is essential to avoid permanent neurologic damage. Herein, we are reporting a case of 66-year-old female patient who presented with insidious onset right-sided frontal headache. Her hospital course progressively worsened and family decision based on her wishes was to refer her to hospice and comfort care. Despite an extensive workup with advanced imaging techniques, no diagnosis was established until postmortem autopsy and histopathology confirmed primary angiitis of the central nervous system.