CT - Brain abscess: A 66 year old man who developed the subacute onset of persistent headache and fever two weeks after undergoing dental surgery. In the panel on the left, an area of hypodensity is seen in the left mesial frontal lobe with left temporal horn dilatation on unenhanced CT scanning. The CT scan with contrast on the right demonstrates ring enhancement often seen in the capsule of a bacterial abscess. The medial and posterior aspects of the occipital horn of the left lateral ventricle also enhance, most likely representing ventriculitis. This patient required surgical drainage and long-term antibiotic treatment.