Multiple sclerosis (MS) is a disease in which the body’s immune system attacks the protective covering surrounding the nerves of the central nervous system. Once considered a disease of the brain’s white matter, recent research has shown that cortical lesions, or lesions in the grey matter of the outer layer of the brain, develop earlier in the course of the disease.
While cortical lesions are not easy to see with conventional 3 Tesla MRI, researchers have now demonstrated that 7 Tesla (7T) MRI can be used to visualize these lesions. They also found that the development of lesions in the cortical grey matter is a powerful predictor of neurological disability for people with MS, and suggest that ultrahigh-field MRI could play an important role in evaluating disease progression (Radiology 2019; 00:1–10).
“Because 7T MRI is more sensitive to cortical lesions than lower-field MRI, we can detect many of these lesions that we couldn’t see before and determine if they are strongly correlated with neurological disability and disease progression,” explains senior author Caterina Mainero from Massachusetts General Hospital. “In this study, we wanted to track the evolution of these lesions and better understand where in the cortex these lesions develop more frequently.”
Mainero and colleagues followed 20 patients with relapsing remitting MS and 13 with secondary progressive MS over time, along with 10 age-matched healthy controls. In relapsing remitting MS, the patient’s symptoms sometimes improve and sometimes worsen, while secondary progressive MS is characterized by more significant disability.
Twenty five MS patients developed new cortical lesions during the follow-up period. And 7T MRI detected these lesions more frequently than lower-field MRI achieved in previous studies. On average, the number of lesions that developed in the cortical region was more than twice the number that developed in the white matter.
The 7T scans revealed that the cortical lesions tended to accumulate in sulci, which are grooves on the brain’s surface. The researchers also observed that the total volume of cortical lesions was a predictor of neurological disability, at both baseline and follow-up assessment. “We found that these lesions can predict disability progression more than white matter lesions, which are the typical lesions of MS we’ve been studying for years,” says Mainero.
The findings suggest that assessment of cortical lesions should become a major component in the evaluation of progression of disease burden in MS. “This can have a very powerful impact on how we monitor patients with MS,” Mainero explains. “We can also use this tool to see how potential treatments can affect the development and evolution of cortical lesions.”
