A new study published last month in Neurology has highlighted a novel biomarker for assessing cognitive decline in individuals with MS.1,2 There are three main pathological events that can occur throughout MS progression, two of which, inflammation and demyelination, can be studied via common imaging techniques. The third, cognitive impairment or degeneration, is not so easily assessed. It has often been thought that the amount of atrophied, or dying, gray matter in the brain was the best indicator of cognitive impairment, however, significant atrophy isn’t often seen until deep into a decline.
Researchers at the Aix-Marseille University Medical School in Marseille, France have discovered a new way to detect cognitive decline from its very beginnings. The researchers used sodium MRI technology to detect the total sodium concentration in various parts of the brain. These parts included lesions, normal-appearing white matter, and gray matter. They also looked at atrophy of gray matter in their study subjects.
What they found, was that of the 58 individuals they studied, 21 were considered cognitively impaired, as opposed to the 37 others who were cognitively preserved. An additional control group was also included for comparison. Of the 21 who were considered impaired, atrophy of gray matter was present, but not to enough of an extent to explain the extremely varied cognitive differences. What was of significant difference, however, was the sodium accumulation levels in the impaired group’s gray matter and normal-appearing white matter, specifically in the left somatosensory association cortex, prefrontal cortices, left middle temporal gyrus, cingulum, and precumeus.
Sodium accumulation in these areas is crucial, as it can indicate a state of “virtual hypoxia” that can be caused by chronically inflamed and demyelinated axons. The sodium accumulation can then lead to calcium accumulation through a cascade of events, which can ultimately lead to cell death. What is crucial though, is that the areas of sodium accumulation present on the imaging, specifically the gray matter, are key in neural integration and brain communication. Basically, indicating issues with the main paths of transferring neural info.
Age and total sodium accumulation predictors of cognitive impairment
Overall, it was concluded that age and total sodium accumulation were the biggest predictors of cognitive impairment and its severity. Other researchers have tried to block sodium channels, but have not prevailed in preventing overall degeneration. Right now, the best methods are through preventing demyelination and chronic inflammation, which is the aim of most drugs on the market. However, this information could aid in the development of new therapies, or even lead to a better predictor of the true onset of cognitive decline, before it progresses to the point of significant atrophy or deficits. More research will need to be done to address the sodium accumulation specifically, and maybe now, can be started at the very first indication of cognitive decline!
Maarouf A, Audoin B, Pariollaud, F, et al. Increased total sodium concentration in gray matter better explains cognition than atrophy in MS. Neurology. Epub ahead of print. December 14, 2016.
Anderson, Pauline. “Brain Sodium Linked to Cognitive Deficits in MS.” Medscape. 28 Dec 2016. Available from: http://www.medscape.com/viewarticle/873803?nlid=111631_2981&src=wnl_dne_161229_mscpedit&uac=259022DR&impID=1264171&faf=1#vp_2