Abstract
Among screening tools for cognitive impairment in large cohorts, the Montreal Cognitive Assessment (MoCA) seems to be more sensitive to early cognitive impairment than the Mini-Mental State Examination (MMSE), particularly after transient ischemic attack or minor stroke. We reasoned that if MoCA-detected early cognitive impairment is pathologically significant, then it should be specifically associated with the presence of white matter hyperintensities (WMHs) and reduced fractional anisotropy (FA) on magnetic resonance imaging. Consecutive eligible patients with transient ischemic attack or minor stroke (Oxford Vascular Study) underwent magnetic resonance imaging and cognitive assessment. We correlated MoCA and MMSE scores with WMH and FA, then specifically studied patients with low MoCA and normal MMSE. Among 400 patients, MoCA and MMSE scores were significantly correlated (all P<0.001) with WMH volumes (rMoCA=-0.336; rMMSE=-0.297) and FA (rMoCA=0.409; rMMSE=0.369) and-on voxel-wise analyses-with WMH in frontal white matter and reduced FA in almost all white matter tracts. However, only the MoCA was independently correlated with WMH volumes (r=-0.183; P<0.001), average FA values (r=0.218; P<0.001), and voxel-wise reduced FA in anterior tracts after controlling for the MMSE. In addition, patients with low MoCA but normal MMSE (n=57) had higher WMH volumes (t=3.1; P=0.002), lower average FA (t=-4.0; P<0.001), and lower voxel-wise FA in almost all white matter tracts than those with normal MoCA and MMSE (n=238). In patients with transient ischemic attack or minor stroke, early cognitive impairment detected with the MoCA but not with the MMSE was independently associated with white matter damage on magnetic resonance imaging, particularly reduced FA.
Highlights
transient ischemic attack (TIA) and minor stroke often cause no long-term physical disability, they are associated with increased longer-term risk of dementia, Vascular Cognitive Impairment (VCI)[1, 2]
In patients with TIA or minor stroke, early cognitive impairment detected with the Montreal Cognitive assessment (MoCA) but not with the Mini-Mental State Examination (MMSE) was independently associated with white matter damage on MRI, reduced fractional anisotropy (FA)
We hypothesised that in patients with TIA and minor stroke, early cognitive impairment shown by low MoCA score but normal MMSE would be associated with lower FA and that the overall correlation with measures of white matter damage would be higher for scores on MoCA than on MMSE
Summary
TIA and minor stroke often cause no long-term physical disability, they are associated with increased longer-term risk of dementia, Vascular Cognitive Impairment (VCI)[1, 2]. WMH has been associated with increased risk of functional impairment, dementia, stroke and death.[12, 13] DTI provides more fine-grained measures of white matter integrity, namely as fractional anisotropy (FA, indicating the deviation from pure isotropic diffusion of 3 water mobility) and mean diffusivity (MD, indicating the magnitude of diffusion of the water molecules) These have been shown to more closely correlate with cognitive deficits in patients with VCI.[8] We hypothesised that in patients with TIA and minor stroke, early cognitive impairment shown by low MoCA score but normal MMSE would be associated with lower FA and that the overall correlation with measures of white matter damage would be higher for scores on MoCA than on MMSE. We reasoned that if MoCA-detected early cognitive impairment is pathologically significant, it should be associated with the presence of white matter hyperintensities (WMH) and reduced fractional anisotropy (FA) on MRI
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