MRI Scans May Detect Cognitive Impairment in Multiple Sclerosis

Standard MRIs might reveal cognitive impairment in MS patients.

Standard MRIs might reveal cognitive impairment in patients with multiple sclerosis (MS).

Retrospective analysis of magnetic resonance imaging (MRI) scans of 51 patients with MS has found that easily visible brain atrophy may serve as a biomarker for cognitive impairment.

The findings could help simplify the difficult task of evaluating whether (and how much) the disease has taken a toll on the mental abilities of newly diagnosed patients and in predicting which of those patients face the highest risk for cognitive degeneration going forward.

Investigators began with images of patients who had undergone comprehensive cognitive assessment at roughly the same time as their scans. They made simple linear measurements of hippocampi, bifrontal ventricular width, third ventricular width, and bicaudate width. They also measured the area of the anterior corpus callosum, mid corpus callosum and posterior corpus callosum.

The investigators then used Pearson's correlations to examine the relationship between these measurements and cognitive test results. They also compared MRI results of the sample’s cognitively-impaired patients and its cognitively-normal patients using Analysis of Covariance.

Bicaudate width and third ventricular width were both negatively correlated with cognitive test performance. Measures of corpus callosai, on the other hand, were positively correlated with cognitive test performance.

Indeed, after controlling for potential con founders, bicaudate span was significantly (and negatively) tied outcomes on measures of immediate recall. Measures of both anterior corpus callosai and posterior corpus callosai were significantly related to measures of verbal fluency, immediate recall and higher executive function. The size of anterior corpus callosai was also significantly associated to results on processing speed tests, while the size of middle corpus callosai was significantly related to tests of immediate recall and higher executive function.

“A biomarker that would help identify those at risk of cognitive impairment, or with only mild impairment, would be a useful tool for clinicians,” the study authors wrote. “This study presents data demonstrating that simple to apply MRI measures of atrophy may serve as biomarkers for cognitive impairment in persons with MS.”

A number of prior studies have reported connections between cognitive impairment and easily calculated results on magnetic transfer imaging (MTI). A 1998 paper from Neurology, for example, found a significant connection (p<0.05) between quantitative volumetric estimates of cerebral lesion load and neurologic impairment in 44 patients. A second paper that appeared in the same year, in the same publication, found that lesion loads on proton density-weighted measurements derived from MTI scans were associated with cognitive decline in 30 different patients.

A 2002 paper from the Journal of Neurological Sciences found moderate correlations between results on a digit modalities test, a verbal fluency test and a spatial recall test and results from diffusion tensor—MRI scans used to measure lesion volume and brain volume.

Such specialized forms of MRI scans are not frequently used, however, so correlations between scan results and cognitive impairment are not widely applicable. A well-documented link between cognitive decline and results on the standard type of MRI scan that is often used to diagnose or evaluate MS would be much more practical, the authors of the new study wrote.

"Developing easy to perform routine MRI measurements as potential surrogates for cognitive impairment in MS" appeared in Clinical Neurology & Neurosurgery.

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