Identification of Vascular Cognitive Impairment

Fig. 32.1

Contribution of amyloid PET positivity to longitudinal cognitive trajectory after stroke [8]. Mixed VCI (mVCI) is characterized by positivity amyloid PET finding (A-4) and delayed decline in MMSE scores during 4-year follow-up. In contrast, patients with pure VCI (pVCI) showed negative amyloid PET imaging, and his MMSE score remained stable. Reproduced by permission of Stroke [8]

Multi-infarct dementia is dementia syndrome caused by recurrent and multiple infarctions, and stroke lesion extent and severity determined the neuropsychological construct. In contrast, strategic infarct dementia is caused by relatively small lesion, which is strategically located in functionally important location such as the anterior limb or genu of internal capsule, caudate nucleus, thalamus, medial frontal lobe, inferomedial temporal lobe, and angular gyrus.

These syndromes are caused by clinically evident stroke, and patients with PSD had suffered from relatively abrupt cognitive decline after stroke, and location and extent of stroke lesions might affect to the development of cognitive impairment.

In contrast, subcortical vascular dementia (sVaD) is difficult to be distinguished from other neurodegenerative dementia syndromes. It showed more gradual decline in cognition compared to other vascular dementia syndromes. It accompanied diffuse subcortical ischemic lesions without clinically evident stroke. It was known to account for major proportion of VCI in epidemiological studies [9]. Slowly progressive memory deficit as well as impairment of processing speed and frontal executive function is a characteristic feature of sVaD. It is difficult to be differentiated with AD; detailed neuroimaging studies might help differentiate these syndromes. Subcortical VaD could be further classified according to the presence of underlying positivity of amyloid imaging. Pure sVaD denotes patients who had confluent white matter hyperintensities without amyloid positivity and consisted of about 68.9% of sVaD patients who aged around 70s [10]. They showed better performances in the delayed recall of both the verbal and visual memory test compared to those with mixed subcortical VCI [10].

32.3 Clinical Evaluation in Patients with VCI

For proper evaluations of VCI, somewhat different approach is needed compared to those in patients with AD. Most stroke survivors have stroke sequelae such as hemiparesis and dysarthria; these neurologic deficits might affect the proper neuropsychological evaluations. For the diagnosis of dementia, determination of activities of daily living impairment is important. However, due to abovementioned stroke sequelae, impairment of activities of daily living should be based on solely cognitive deficit, not based on physical barriers. Furthermore, most diagnostic criteria did not give any specific cutoff values for “cognitive impairment”; thus, various cutoffs, such as below −1.5 SD or 10 percentile from age-, education-adjusted mean, have been adopted in previous studies. Recently, VasCog statement and DSM-5 have suggested below −2 SD as proper criteria for “cognitive impairment.”

There are various tools to briefly evaluate cognitive function. Firstly, the most representative screening tool is Mini-Mental State Examination (MMSE). It can be conducted within 5 or 10 min and has many supporting evidences of which have used it as cognitive screening tool. However, it has shortcomings that frontal function could not be assessed properly, because MMSE has focused on orientation, memory, and language-related functions. Montreal Cognitive Assessment (MoCA) is another brief screening tool, and it could be conducted in around 15 min. It had alternating trail making, cube, and clock tasks, which improve sensitivity to detect frontal dysfunction. Both MMSE and MoCA require intact motor and visual function. Thus, patients with hemiparesis or visual field defect could not complete the test properly. Several tests, which are 5-min National Institute of Neurological Disorders and Stroke-Canadian Stroke Network protocol and Six-Item Screener, are consisted of only verbally conducted tasks and are capable to be conducted in those with dominant hand weakness and visual field defect.

In cases of below age-, educated-adjusted norm in brief screening test, detailed neuropsychological tests are required to identify domain-specific cognitive impairment and magnitude of deficits. For those with VCI, National Institute of Neurological Disorders and Stroke-Canadian Stroke Network has proposed the Vascular Cognitive Impairment Harmonization Standards—Neuropsychological Protocol (VCIHS-NP) as standard tests to evaluate cognitive function [11]. It is consisted of 5-, 30-, and 60-min protocol, and 5-min protocol is a constellation of subtests of MoCA. Detailed test of each protocol is listed in Table 32.1.

Table. 32.1

Vascular cognitive impairment harmonization standards—Neuropsychological protocol [11]

5-Minute Protocol

MoCA subtests

5-Word Memory Task (registration, recall, recognition)

6-Item Orientation

1-Letter Phonemic Fluency

30-Minute Test Protocol

Semantic Fluency (Animal Naming)

Phonemic Fluency (Controlled Oral Word Association Test)

Digit Symbol-Coding from the Wechsler Adult Intelligence Scale, Third Edition

Hopkins Verbal Learning Test

Center for Epidemiologic Studies Depression Scale

Neuropsychiatric Inventory, Questionnaire Version (NPI-Q)

Supplemental: MMSE, Trail Making Test

60-Minute Test Protocol

Executive/Activation

Animal Naming (Semantic Fluency)

Controlled Oral Word Association Test

WAIS-III Digit Symbol-Coding

Trail Making Test

List Learning Test Strategies

Future Use: Simple and Choice Reaction Time

Language/Lexical Retrieval

Boston Naming Test, Second Edition, Short Form

Visuospatial

Rey-Osterrieth Complex Figure Copy

Supplemental: Complex Figure Memory

Memory

Hopkins Verbal Learning Test-Revised

Alternate: California Verbal Learning Test–2

Supplemental: Boston Naming Test Recognition

Supplemental: Digit Symbol-Coding Incidental Learning

Neuropsychiatric/Depressive Symptoms

Neuropsychiatric Inventory, Questionnaire Version

Center for Epidemiological Studies Depression Scale

Others

Informant Questionnaire on Cognitive Decline in the Elderly, Short Form

MMSE

VCIHS-NP was proposed as a reliable evaluation tool for multinational, multicenter trials and was consisted of sensitive and proper tests for patients with VCI, and many countries have published local norm and validation data. In addition, Alzheimer’s Disease Assessment Scale-Cognitive (ADAS-Cog) and Consortium to Establish A Registry for Alzheimer’s Disease (CERAD) which are usually used in patients in degenerative dementia have been used for cognitive evaluation for VCI. VDAS-Cog, a modified version of ADAS-Cog, Cambridge Cognition Examination (CAMCOG), and several computerized cognitive evaluation tools are also used.

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