Imaging Brain Metabolites May Help Diagnose, Monitor MS
A new imaging technique called magnetic resonance spectroscopic imaging, or MRSI, could be useful for diagnosing and monitoring multiple sclerosis (MS), according to a small study.
“If confirmed in longitudinal clinical studies, this new neuroimaging technique could become a standard imaging tool for initial diagnosis, for disease progression and therapy monitoring of multiple sclerosis patients and, in concert with established MRI, might contribute to neurologists’ treatment strategies,” Wolfgang Bogner, PhD, a senior author of the study from the Medical University of Vienna, in Austria, said in a press release.
Imaging the brain via magnetic resonance imaging, called MRI, is a standard part of diagnosing and monitoring MS. But while MRI can detect brain lesions — relatively large areas of inflammation and/or damage — it is not well-suited for detecting more subtle changes in brain health.
A related imaging technique, MRSI — conceptually — allows for the visualization of metabolites in the brain. “Metabolite” is a broad term that basically refers to small molecules that are produced in the process of cellular activities.
MRSI “enables the detection of changes in the brain of multiple sclerosis patients in regions that appear inconspicuous on conventional MRI,” Bogner said.
“Some neurochemical changes, particularly those associated with neuroinflammation, occur early in the course of the disease and may not only be correlated with disability, but also be predictive of further progression such as the formation of multiple sclerosis lesions,” added Eva Heckova, PhD, the study’s lead author who, like Bogner, is from Medical University of Vienna’s High Field MR Centre.
In this study, Bogner, Heckova, and colleagues used MRSI to image the brains of 65 people with MS — 61 with relapsing-remitting and four with secondary progressive MS. The group included 31 men and 34 women, with a median age of 32. For comparison, 20 people without MS who were matched in terms of age and sex also were analyzed.
The researchers specifically focused on metabolite levels in normal-appearing white matter in the participants’ brains. The white matter of the brain contains connections between different brain regions. It gets its name from the whitish myelin that surrounds nerve fibers and helps them send electrical signals; MS is caused by the immune system erroneously attacking the myelin sheath.
The results showed that, compared with healthy controls, MS patients had markedly lower levels of a metabolite called N-acetylaspartate (NAA).
“Because NAA is almost exclusively present in neurons [nerve cells], lower levels of this metabolite have been interpreted as evidence of impaired axonal [nerve fiber] and/or neuronal integrity,” the researchers wrote.
The MS patients also had markedly higher levels of another metabolite, myo-inositol (mI). According to the researchers, high mI levels are indicative of inflammation in the brain.
Compared with healthy controls, MS patients had higher mI/NAA ratios — even patients in the early stages of the disease who had minimal disability. Statistical analyses indicated that a higher mI/NAA ratio in several regions of normal-appearing white matter was associated with more severe disability among MS patients, as assessed with the Expanded Disability Status Scale (EDSS).
“The visualized changes in neurochemistry of normal-appearing brain tissue correlated with the patients’ disabilities,” Bogner said.
Using MRSI to measure these metabolites “can help to depict and visualize pathologic [disease-related] manifestations of multiple sclerosis beyond [lesions visible with standard MRI] that are associated with clinically measured disability,” the researchers concluded.