Diffusion tensor imaging suggests subcortical disconnection within large-scale cognitive neural networks is a key mechanism of vascular cognitive disorder, according to a study in Radiology.
Researchers from the United Kingdom investigated associations between neuroimaging markers of cerebrovascular disease, including lesion topography and extent and severity of strategic and global cerebral tissue injury, and cognition in carotid artery disease (CAD).
A total of 108 patients with symptomatic CAD participated in the study; 53 were cognitively impaired. All underwent MRI and the Addenbrooke’s Cognitive Examination–Revised. The researchers assessed group comparison and interrelations between global cognitive and fluency performance, lesion topography, and ultrastructural damage. Associations between cognition, medial temporal lobe atrophy (MTA), lesion volumes, and global white matter ultrastructural damage indexed as increased mean diffusivity were tested with regression analysis by controlling for age. Diagnostic accuracy of imaging markers selected from a multivariate prediction model was tested with receiver operating characteristic analysis.
The results showed that the 53 cognitively impaired patients, classified as having probable vascular cognitive disorder, were older than nonimpaired patients. They also had:
• More frequent MTA
• More cortical infarctions
• Larger volumes of acute and chronic subcortical ischemic lesions
Lesion volumes did not correlate with global cognitive performance (lacunar infarctions, acute lesions, and chronic subcortical ischemic lesions. In contrast, cognitive performance correlated with presence of chronic ischemic lesions within the interhemispheric tracts and thalamic radiation. Skeleton mean diffusivity showed the closest correlation with cognition and promising diagnostic accuracy for vascular cognitive disorder. Findings were confirmed in subjects with a low risk of preclinical Alzheimer disease indexed by the absence of MTA (n = 85).
"Using standard clinical brain MRI, we found that microscopic damage of main white matter tracts allowed us to distinguish patients with symptomatic carotid artery disease and cognitive impairment from those who were cognitively intact," senior author, Dorothee P. Auer, PhD, of the University of Nottingham, said in a news release. "Our findings mean that a simple MRI test might improve the diagnostic work-up of people with suspected vascular cognitive disorder, and holds further promise to track progression of the disorder." =
"This will be a critical step in the quest for prevention of vascular dementia, by helping to identify those at risk, and by enabling imaging studies to evaluate the effectiveness of interventions," co-author Dewen Meng, MSc, of the University of Nottingham, added.
The researchers concluded that subcortical white matter ischemic lesion locations and severity of ultrastructural tract damage contribute to cognitive impairment in symptomatic CAD, which suggests that subcortical disconnection within large-scale cognitive neural networks is a key mechanism of vascular cognitive disorder.