Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that uses strong magnetic fields and radio waves to generate detailed images of organs and tissues. This technology provides clear, high-resolution pictures, particularly useful for examining the brain and spinal cord. For multiple sclerosis (MS), MRI is a powerful tool, allowing healthcare professionals to observe changes within the central nervous system. It is an indispensable part of understanding and managing MS.
Identifying MS Lesions on an MRI
Multiple sclerosis is characterized by inflammation and damage to myelin, the protective sheath around nerve fibers in the brain and spinal cord. This damage appears on MRI scans as distinct areas called lesions or plaques. Radiologists look for these lesions as bright white spots on specific MRI sequences, such as T2-weighted and FLAIR (Fluid-Attenuated Inversion Recovery) images. The FLAIR sequence is highly sensitive for detecting lesions in the cerebral hemispheres by suppressing the signal from cerebrospinal fluid, making lesions appear more prominent.
Lesions commonly appear in specific regions of the central nervous system, providing clues for MS. They are frequently found near the brain’s ventricles (periventricular lesions) and directly beneath the brain’s outer layer (juxtacortical lesions). Lesions can also be observed in the infratentorial regions, including the brainstem and cerebellum, and within the spinal cord, particularly in the cervical segment. Finding lesions in these characteristic locations helps differentiate MS from other conditions.
The Role of MRI in Diagnosing Multiple Sclerosis
Beyond identifying lesions, MRI plays a central role in confirming an MS diagnosis by demonstrating how these lesions are distributed in space and time. This concept is referred to as “dissemination in space” (DIS) and “dissemination in time” (DIT). Dissemination in space means lesions are present in multiple distinct central nervous system areas typical for MS, such as the periventricular, juxtacortical, infratentorial, and spinal cord regions. A diagnosis requires at least one lesion in two or more of these four characteristic locations.
Dissemination in time indicates lesions have occurred at different points, suggesting ongoing disease activity rather than a single event. This can be shown by the simultaneous presence of actively inflamed (new) and older lesions, or by new lesions appearing on a follow-up MRI compared to an earlier scan. By fulfilling both dissemination in space and time criteria through MRI findings and clinical evaluation, a neurologist can make an accurate MS diagnosis. These principles form the basis of established diagnostic guidelines, allowing for an earlier and more precise diagnosis.
Tracking Disease Activity and Progression
After an initial diagnosis, regular MRI scans are important for monitoring disease activity and progression over time. These follow-up MRIs help determine if new lesions have formed or existing ones have changed, which guides treatment decisions. Differentiating between new lesions and older, stable ones is a primary objective of these scans.
To highlight active inflammation, a contrast agent containing gadolinium is often administered intravenously before or during the scan. This dye accumulates where the blood-brain barrier is disrupted, causing “active” lesions to appear as bright, enhancing spots on the MRI. The presence of enhancing lesions signifies ongoing disease activity, even without new symptoms. Monitoring the number and volume of these enhancing lesions helps assess the effectiveness of disease-modifying therapies.
Another measure tracked over time is brain volume loss, also known as brain atrophy. This atrophy, particularly in gray matter structures, can correlate with long-term disability progression. Tracking these changes provides insights into the neurodegenerative aspects of MS and helps evaluate treatment efficacy.
Understanding Your MRI Report
When reviewing an MRI report for multiple sclerosis, certain terms commonly appear. “T2 hyperintensities” describes the bright white spots representing MS lesions on T2-weighted and FLAIR sequences. These indicate areas of inflammation, demyelination, and tissue damage. The total number and volume of these lesions are often noted in the report.
Another term is “T1 hypointensities,” often referred to as “black holes.” These darker spots on T1-weighted images signify more severe or older tissue damage, including axonal loss. Their presence suggests chronic lesions linked to increased disability. “Brain parenchymal volume” refers to the overall size of the brain tissue, and changes in this measurement can indicate atrophy, reflecting the long-term impact of the disease. Discussing these terms with your neurologist can provide clarity on your specific MRI results.