By Mayo Clinic Staff

A brain lesion is an abnormality seen on a brain-imaging test, such as magnetic resonance imaging (MRI) or a computerized tomography (CT) scan. On CT or MRI scans, brain lesions appear as dark or light spots that don't look like normal brain tissue.

Usually, a brain lesion is an incidental finding unrelated to the condition or symptom that led to the imaging test in the first place.

A brain lesion may involve small to large areas of your brain, and the severity of the underlying condition may range from relatively minor to life-threatening.

Dec. 04, 2014