Medically reviewed on January 11, 2018
A brain lesion is an abnormality seen on a brain-imaging test, such as magnetic resonance imaging (MRI) or computerized tomography (CT). 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.
Brain lesions seen on MRI may indicate any number of possible conditions. Here the brain lesion depicts tissue damage from an ischemic stroke — a state of severely reduced blood flow to the brain, which deprives brain cells of vital oxygen and nutrients.
Often, a brain lesion has a characteristic appearance that will help your doctor determine its cause. Sometimes the cause of the abnormal-appearing area cannot be diagnosed by the image alone, and additional or follow-up tests may be necessary.
Among the known possible causes of brain lesions are:
- Brain aneurysm (a bulge in an artery in your brain)
- Brain AVM (arteriovenous malformation) — an abnormal formation of brain blood vessels
- Brain tumor (both cancerous and noncancerous)
- Encephalitis (brain inflammation)
- Hydrocephalus (a congenital brain abnormality)
- Multiple sclerosis
- Traumatic brain injury
While brain trauma of any sort may result in a concussion as well as a brain lesion, concussions and brain lesions are not the same thing. Concussions more often occur without ever causing any changes on the CT or MRI and are diagnosed by symptoms rather than imaging tests.
When to see a doctor
If a brain lesion discovered during a brain-imaging test doesn't appear to be from a benign or resolved condition, your doctor will likely seek more information from additional testing or consulting a specialist.
Your doctor may recommend that you see a neurologist for a specialized examination and, possibly, further tests. Even if a neurological work-up doesn't result in a diagnosis, your doctor may recommend continued testing to reach a diagnosis or follow-up imaging tests at regular intervals to monitor the lesion.