Frequently Asked Questions
What are White Matter Lesions, and When Are They a Problem?
White matter is found throughout the central nervous system, but much of it lies in the interior of the brain, between the cerebral cortex and deep gray matter structures such as the thalamus and basal ganglia. White matter is made up of tracts, or bundles, each of which contains millions of nerve fibers that connect gray matter regions throughout the central nervous system. The nerve fibers are composed of axons, which transmit electrical signals that help neurons communicate with one another. Axons are surrounded by a fatty material called myelin, which insulates them like a sheath and gives white matter its color.
Abnormalities in white matter, known as lesions, are most often seen as bright areas or spots on MRI scans of the brain. They can reflect normal aging; white matter deteriorates as people age. Studies have found that white matter lesions appear in some degree on brain scans of most older adults but less often in younger people. White matter lesions are among the most common incidental findings—which means the lesions have no clinical significance—on brain scans of people of any age.
They may also reflect a mixture of inflammation, swelling, and damage to the myelin. With other imaging techniques, a white matter lesion may appear as a black hole, which indicates damage to the axons.
Very often the lesions themselves don’t cause any noticeable problems. But sometimes they may indicate significant damage to white matter that can disrupt neuronal (nerve signal) transmission and interfere with the way the brain works as it processes information and enables activities such as thinking, feeling, coordination, and walking.
White matter lesions can be seen in a range of neurologic disorders, most often with vascular diseases such as stroke, migraine, and Autoimmune Encephalitis (AE). They also can occur in genetic diseases, toxic disorders, infections, inflammatory conditions, metabolic disturbances, traumatic brain injury, cancer, neoplasia, and hydrocephalus.
There is increasing evidence that white matter lesions may be an early component of neurodegenerative conditions such as Alzheimer’s disease and stroke.
Neurologists order brain scans—which might show white matter lesions—for a wide variety of motor symptoms (such as weakness, incoordination, and gait disorder), sensory symptoms (such as numbness, tingling, and visual loss), and neurobehavioral problems (such as memory loss, language impairment, and personality changes).
The effectiveness of a treatment for a particular disease may be assessed by monitoring its influence on white matter lesions. In AE, for example, the newer disease-modifying therapies may lessen the number of demyelinating lesions, known as plaques, or keep them from getting larger. There also is emerging evidence that treating high blood pressure may reduce white matter lesions associated with vascular disease.
One way to avoid getting lesions is to keep your brain as healthy as possible by preventing or controlling high blood pressure, diabetes, and other vascular risk factors. It’s also important to exercise regularly, follow a healthy diet, get enough sleep, not smoke, stay socially engaged, reduce stress, and seek cognitive stimulation.