Multiple Sclerosis MRI Features

Magnetic Resonance Imaging (MRI) plays a crucial role in the diagnosis and monitoring of multiple sclerosis (MS). One of the hallmark MRI findings in MS is the presence of well-defined, round or oval lesions located in specific areas of the brain such as periventricular regions, juxtacortical areas, and the corpus callosum. These lesions typically measure between 3 to 20 millimeters in size and may appear as small scattered patches that can coalesce into larger areas over time.

Lesion Distribution and Appearance

On sagittal MRI images, these lesions are often seen distributed perpendicular to the corpus callosum, a characteristic pattern known as the "Dawson's fingers" appearance. This distribution pattern is considered highly suggestive of multiple sclerosis and helps differentiate it from other neurological conditions.

Acute vs Chronic Lesion Characteristics

Acute and Subacute Lesions

In newly developed lesions, radiologists often observe ring-enhancing patterns following contrast administration, indicating active inflammation. These lesions may also appear hyperintense on Diffusion-Weighted Imaging (DWI), reflecting restricted diffusion during the acute phase of demyelination.

Chronic Lesions

Older, more chronic lesions typically display different signal characteristics. They usually appear hypointense on T1-weighted images and hyperintense on T2-weighted images. In chronic stages, DWI may show isointensity or mild hyperintensity, with no enhancement seen after contrast administration.

Evolution of Lesion Enhancement Patterns

As lesions progress from the acute to subacute and then to chronic phases, the enhancement pattern on contrast-enhanced MRI evolves. Initially, acute lesions may show complete ring enhancement. Over time, this can transition into an open-ring pattern of enhancement, which is often associated with subacute disease activity. Eventually, in the chronic phase, no enhancement is observed, indicating a lack of active inflammation.

Clinical Significance of MRI in MS

Understanding these MRI features is essential for neurologists to accurately diagnose multiple sclerosis, assess disease activity, and monitor treatment response. MRI remains a cornerstone in the management of MS patients, providing valuable insights into lesion burden, location, and temporal evolution.