What do spots on brain MRI mean?

Brain MRIs are medical imaging tests that allow doctors to see detailed pictures of the brain and surrounding structures. They use strong magnetic fields and radio waves to create detailed cross-sectional images of the brain. MRIs are often used to diagnose and monitor conditions affecting the brain such as tumors, bleeding, swelling, or infection.

Sometimes when looking at a brain MRI, the radiologist may notice spots or lesions on the images. There are many possible reasons for spots showing up on a brain MRI. Some are normal findings, while others may represent more serious underlying conditions. Understanding what certain spots or lesions mean on a brain MRI can help provide important information about a person’s health.

Table of Contents

Common Causes of Spots on Brain MRI

Here are some of the most common reasons spots may appear on a brain MRI:

Aging: As people get older, the brain naturally atrophies and the ventricles (fluid-filled spaces in the brain) enlarge. This can cause various small spots or areas of brightness to appear on MRI images. These are usually not a cause for concern if the person is older and otherwise healthy.
Migraines: People who experience migraines sometimes develop small white matter lesions in their brain that appear as bright spots on MRI. This is thought to be due to the effects of chronic migraines on the brain’s blood vessels.

Small vessel ischemic disease: This condition causes tiny blockages in the small blood vessels in the brain. It results in small spots appearing on MRI, most often in the basal ganglia and white matter of the brain.
Multiple sclerosis (MS): MS is a disease where the immune system attacks the myelin sheaths that protect nerve fibers. This causes scar tissue called sclerosis. On MRI, these damaged areas appear as bright spots called plaques or lesions.
Brain tumor: Both cancerous and non-cancerous brain tumors will appear as lesions with varying degrees of brightness on MRI. The borders and locations of tumors provide clues about whether they are likely cancerous.

Abscess: An abscess in the brain appears as a ring-enhancing lesion, meaning there is a bright spot in the center surrounded by a ring of inflammation.
Stroke: If a person has a stroke, the area of damaged brain tissue will appear darker on MRI than the surrounding tissue.
Trauma: Head trauma that causes bleeding, swelling or damage in the brain can result in spots on MRI. The location often provides clues about which type of trauma occurred.

What Do Different Types of Spots Mean?

The radiologist pays close attention to the appearance, size, location, and number of spots seen on the MRI when making a diagnosis. Here is more information about what different types of spots may indicate:

Bright Spots

Multiple small bright spots in the white matter are often seen with small vessel ischemic disease.
Larger, asymmetric bright spots may indicate an MS plaque or tumor.

Ring-enhancing bright spots are typical of abscesses.
Bright spots on the boundary between gray and white matter are common with migraines.

Dark Spots

Dark spots in the basal ganglia may indicate small vessel ischemic disease or other vascular pathology.

Dark spots at the site of a stroke indicate dead tissue.
Some tumors may appear darker than surrounding tissue.
Post-traumatic dark spots are due to bleeding or tissue damage.

Enlarged Spaces

Enlarged ventricles often occur due to aging atrophy.
After a stroke, an enlarged ventricle may indicate volume loss.
Some dark tumors are cystic, leading to enlarged spaces.

Location of Spots

Spots in the temporal and occipital lobes may indicate MS.
Spots in the frontal and parietal lobes are more typical of small vessel disease.
Brain tumors and abscesses appear in diverse locations.

Strokes happen in specific vascular territories.

Are Spots on Brain MRI Serious?

Seeing spots on a brain MRI can be alarming, but it does not necessarily mean there is a serious underlying problem. Many benign things can cause spots to appear. The radiologist takes into account the size, type, location and pattern of spots seen in order to determine if they are likely worrisome or not. Here are some general guidelines:

Multiple small bright spots in an older patient are usually not serious.

A few tiny dark spots in the basal ganglia of an elderly person are likely benign.
One or two bright spots on their own, without other findings, may be normal.
Any rapidly growing or enlarging spots need urgent evaluation.

Dark spots associated with neurological symptoms (weakness, speech issues, vision loss) typically need prompt assessment.
Ring-enhancing bright spots often require biopsy to rule out cancer vs. abscess.

In summary, the more spots present, the larger their size, and the more atypical their location, the more likely they represent a serious underlying problem. Any spots that appear suspicious or worrisome based on the radiology report should be evaluated by a neurologist.

What Other Findings Help Diagnose Spot Cause?

The MRI radiologist does not make a diagnosis based only on the spots seen on the scan. They also take into account other associated imaging findings and clinical information. Some examples include:

Atrophy (shrinkage) of the surrounding brain tissue may indicate an old stroke or chronic small vessel disease.
Increased overall white matter signal often accompanies chronic small vessel ischemic changes.

Loss of gray-white differentiation can be seen with demyelinating processes like MS.
Mass effect, or compression/shifting of surrounding brain structures, points to a space-occupying tumor or abscess.
Associated hemorrhage suggests traumatic injury, stroke, or tumor bleeding.

Known history of immune deficiency makes infection more likely.
Headache and cognitive symptoms make demyelinating disease more probable.

Correlating the MRI findings with the person’s medical history and reported symptoms enables the radiologist to narrow down the differential diagnosis and determine if clinical follow up is advised.

Conclusion

Spotting spots on a brain MRI is very common and only sometimes indicates an actual problem. Small bright or dark spots in older individuals are typically benign. However, enlarging/new spots, spots associated with symptoms, and atypical appearing or located spots may need medical assessment. The MRI radiologist examines all aspects of the spots and related findings to advise if further evaluation is recommended.