Dementia and Cerebrovascular Disease

(1)

Department of Medical Gerontology, Trinity College, Dublin, Dublin, Ireland

(2)

Department of Medical Gerontology, Mercer’s Institute for Successful Ageing, St James’s Hospital, Dublin, Ireland

(3)

Medical Gerontology, Trinity College, Dublin, Dublin, Ireland

(4)

Acute Medical Unit, Tallaght Hospital, Dublin, Ireland

Keywords

Cerebrovascular diseaseHypertensionDiabetesDementiaNeuroimaging

5.1 Introduction

The nature of the association between cerebrovascular disease (CVD) and dementia has been debated for many years. At one point, CVD was considered the dominant cause of dementia, then, it was conversely thought in fact to be an uncommon cause. Vascular dementia (VaD) is a heterogeneous term and comprises dementias resulting from all types of vascular pathologies: cortical vascular dementia; subcortical ischemic dementia; strategic-infarct dementia; hypoperfusion dementia; haemorrhagic dementia; and dementias resulting from specific arteriopathies.

Under the most widely accepted diagnostic criteria the diagnosis of VaD requires the presence of cognitive decline (loss of memory and deficits in at least two other domains) resulting in impaired functional abilities. Evidence of CVD must be confirmed by neuro-imaging for a diagnosis of probable VaD, and the onset of dementia and CVD must be reasonably related temporally. Several specific diagnostic criteria are used to assist the diagnosis of VaD including the Diagnostic Manual on Mental Disorders, 5^th edition (DSM-V) criteria, the International Classification of Diseases, 10th edition (ICD-10), the National Institute of Neurological Disorders and Stroke Association International pour le Recherché at L’Enseignement en Neurosciences (NINCDS-ARIEN) criteria, and the Hachinski Ischemic score. Unfortunately however, as with many neurocognitive disorders, consistency of diagnosis between these tools and with neuroimaging is poor. For example, a population based clinic-pathologic study in the United Kingdom, found that the NINCDS-ARIEN diagnostic criteria had a sensitivity of 43 % and a specificity of 95 %. Similarly, in a US based cohort study of patients diagnosed with dementia, application of the NINCDS-ARIEN criteria gave a proportionate risk for VaD of 4 %, whereas application of the DSM-IV criteria in the same patient population gave a rate of VaD of 29 %. Neither estimate correlated closely with the ultimate neuropathologic diagnosis. Overall the NINCDS-ARIEN criteria appear to be the most specific (see Table 5.1), and are used most commonly in research. The Hachinski Score (Table 5.2) is a useful tool for distinguishing between Alzheimer’s Type Dementia and Vascular Dementia with about a 90 % sensitivity and specificity for this determination with a score ≥7 being suggestive of Vascular dementia. It is understandably less useful in distinguishing from mixed types. Unlike the NINDS ARIEN criteria it does not require the availability of brain imaging to apply.

Table 5.1

NINDS-ARIEN criteria for diagnosing vascular dementia

Cerebrovascular disease

Focal central nervous system signs

Evidence of cerebrovascular disease by neuroimaging

A relationship between the two manifest by one or more of the following

Dementia onset within 3 months after having a stroke

Abrupt deterioration in cognition or fluctuating stepwise course

Table 5.2

Hachinski ischaemic score

Item no.	Description	Value
1	Abrupt onset	2
2	Stepwise deterioration	1
3	Fluctuating course	2
4	Nocturnal confusion	1
5	Preservation of personality	1
6	Depression	1
7	Somatic complaints	1
8	Emotional incontinence	1
9	History of hypertension	1
10	History of stroke	2
11	Associated atherosclerosis	1
12	Focal neurological symptoms	2
13	Focal neurological signs	2

Items distinguishing vascular dementia from Alzheimer’s Dementia: fluctuating course (odds ratio (OR): 7.6), stepwise deterioration (OR: 6.1), focal neurological symptoms (OR: 4.4), hypertension (OR: 4.3) and history of stroke (OR, 4.30)

As not all patients fulfil the strict criteria for dementia, and many may be significantly cognitively impaired without memory loss, the term vascular cognitive impairment (VCI) has been suggested and reinforced in the recent DSM V criteria. VCI includes VaD, but also encompasses mixed Alzheimer’s disease (AD) and VaD as well as vascular cognitive impairment without dementia and hereditary disorders.

5.2 Prevalence

VaD is historically considered the second most common cause of dementia in the elderly after AD. Between 1 and 4 % of people over 65 years suffer from VaD and the prevalence appears to double every 5–10 years after the age of 65 years. Although the prevalence increases more with age than Alzheimer’s dementia, no large population cohort has been studied to date in any ethnic or racial group where prevalence of VaD exceeds that of Alzheimers. Cognitive decline of any severity may be present in over 80 % of stroke patients ranging in age from 55 to 85 year. Prevalence of post stroke dementia depends on criteria used but probably exceeds 30 %. While it is clear that AD and VaD often co-exist in the elderly population, it has been much harder to estimate the prevalence of this “mixed dementia”. Autopsy series report that co-existing vascular pathology occurs in 24–28 % of AD cases and conversely half of patients with vascular disease who become demented also have AD pathology. Patients often have clinical features of both AD and VaD, and both conditions share similar risk factors and pathogenic mechanisms.

5.3 Clinical Features

Due to the variety of pathogenic mechanisms, the clinical manifestations of VaD can be varied and are determined by the size, location, and type of cerebral damage. There are several conditions that can mimic the appearance of dementia which should always be excluded at the outset of investigation (see Table 5.3). Classically the clinical features include an abrupt onset, stepwise deterioration, fluctuating course, and are often accompanied by focal motor and sensory abnormalities including early onset of urinary incontinence and gait disorders (see Table 5.4). However subcortical VaD can present with a gradual onset and deterioration similar to the pattern seen in AD. Even within VaD, the clinical features can be further subdivided:

Table 5.3

Conditions which can mimic dementia