A cerebral abscess is most often a complication of an infection, such as pneumonia or endocarditis, with onset days to weeks earlier. The bacteria spread hematogenously. As the abscess organizes, it is ringed by fibroblasts that deposit collagen; this feature is characteristic of an abscess in the CNS. A neoplasm occasionally may be ring-enhancing, but glioblastoma is an aggressive malignancy that is not well demarcated. Metastases are mass lesions that are typically multifocal. A multiple sclerosis plaques is generally not large, is found in white matter, and does not typically have ring enhancement. An infarct would produce sudden signs and symptoms that improve over time, and the CSF protein would not be increased.