White matter hyperintensities (WMH) seen on brain magnetic resonance imaging (MRI) of healthy, elderly patients have been associated with vascular risk factors. Potential mechanisms by which WMH lead to symptoms include atrophy of previously connected cortex and network dysfunction. In this study, Tuladhar et alevaluated the relationship between WMH, cortical morphology and cognition in older, non-demented patients with cerebral small vessel disease (e.g. WMH).
Data from 426 individuals, age 50-85 years, with WMH and/or lacunar infarct on MRI was analyzed from the Radbound University Nijmegen Diffusion Tensor MRI Prospective Cohort Study. Vascular risk factor assessment and detailed neuropsychological testing was completed on all enrolled. All subjects’ MRI was obtained on the same scanner. Two blinded raters calculated MRI WMH load and cortical thickness (CT) was measured by imaging analysis software.
WMH burden was negatively correlated with bilateral fronto-temporal region CT but positively correlated with paracentral region CT (even after adjusting for vascular risk factors) (p<0.05). WMH distribution was associated with regional CT – for example, the burden in the corpus callosum, internal capsule, corona radiata, posterior thalamic radiation, and superior longitudinal fasciculus was negatively correlated with CT in the fronto-temporal regions. The authors additionally demonstrated that thinner CT was related to worse cognitive performance (including mini-mental status exam, verbal memory, fluency, attention); this remained true after adjusting for age, gender, education, and also WMH. Though WMH was associated with the higher intellectual functions testing, the relationship was no longer significant when controlling for CT.
This report provides further evidence on how vascular disease may affect cognition. It is important to remember that the findings are cross-sectional, correlative, and hypothesis-generating. Future studies will have to elucidate the pathophysiology of cortical atrophy in those with WMH and determine what other factors contribute to it.