CNS Infections

CNS infection includes:

abscesses (mass lesions with surrounding edema)
encephalitis or myelitis (inflammation, often viral, of the brain or spinal cord, appearing bright on T2 weighted or FLAIR series MRI)
meningitis (which may be noted as contrast enhancement of leptomeninges on MRI).

Pyogenic Abscess

Findings: An enhancing ring lesion within the left posterior frontal lobe.
Differential diagnosis: Metastasis. Since abscess cannot be differentiated clearly from metastasis by MRI imaging, appropriate history and clinical findings are needed to aid in accurate diagnosis. A surgical biopsy may eventually be required.