Many individuals with major or mild vascular NCD present with multiple infarctions, with an acute stepwise or ﬂuctuating decline in cognition, and intervening periods of stability and even some improvement. Others may have gradual onset with slow pro- gression, a rapid development of deficits followed by relative stability, or another complex presentation. Major or mild vascular NCD with a gradual onset and slow progression is generally due to small vessel disease leading to lesions in the white matter, basal ganglia, and/ or thalamus. The gradual progression in these cases is often punctuated by acute events that leave subtle neurological deficits. The cognitive deficits in these cases can be at- tributed to disruption of cortical-subcortical circuits, and complex attention, particularly speed of information processing, and executive ability are likely to be affected.
Assessing for the presence of sufficient cerebrovascular disease relies on history, phys- ical examination, and neuroimaging (Criterion C). Etiological certainty requires the dem- onstration of abnormalities on neuroimaging. The lack of neuroimaging can result in ter lesions. However, if the neurocognitive impairment is temporally associated with one or more well-documented strokes, a probable diagnosis can be made in the absence of neu- roimaging. Clinical evidence of cerebrovascular disease includes documented history of stroke, with cognitive decline temporally associated with the event, or physical signs con- sistent with stroke (e.g., hemiparesis; pseudobulbar syndrome, visual field defect). Neuro- cerebrovascular disease comprises one or more of the following: one or more large vessel infarcts or hemorrhages, a strategically placed single infarct or hemorrhage (e.g., in angu- lar gyms, thalamus, basal forebrain), two or more lacunar infarcts outside the brain stem, or extensive and conﬂuent white matter lesions. The latter is often termed small vessel dis- ease or subcortical ischemic changes on clinical neuroimaging evaluations.
For mild vascular NCD, history of a single stroke or extensive white matter disease is gen- erally sufficient. For major vascular NCD, two or more strokes, a strategically placed stroke, or a combination of white matter disease and one or more lacunes is generally necessary.
The disorder must not be better explained by another disorder. For example, promi- nent memory deficit early in the course might suggest Alzheimer's disease, early and prominent parkinsonian features would suggest Parkinson's disease, and a close associa- tion between onset and depression would suggest depression.
A neurological assessment often reveals history of stroke and/ or transient ischemic epi- sodes, and signs indicative of brain infarctions. Also commonly associated are personality and mood changes, abulia, depression, and emotional lability. The development of late- function is a common presentation among older adults with progressive small vessel isch- emic disease (”vascular depression”).
Major or mild vascular NCD is the second most common cause of NCD after Alzheimer’s disease. In the United States, population prevalence estimates for vascular dementia range from 0.2% in the 65—70 years age group to 16% in individuals 80 years and older. Within 3 months following stroke, 20%—30% of individuals are diagnosed with dementia. In neu- ropathology series, the prevalence of vascular dementia increases from 13% at age 70 years to 44.6% at age 90 years or older, in comparison with Alzheimer’s disease (23.6%—51%) and combined vascular dementia and Alzheimer’s disease (2%—46.4%). Higher prevalence has been reported in African Americans compared with Caucasians, and in East Asian countries (e.g., Japan, China). Prevalence is higher in males than in females.