Difference Between Vascular Dementia and Alzheimer's Disease

The difference between vascular dementia and Alzheimer's disease is not a straightforward one. First, the history can be helpful in distinguishing the two. In people with vascular dementia, the onset can be quite sudden with a step-wise decline over time, indicating sudden periods of deterioration, probably equating with episodes of stroke or transient ischaemic attack (where someone gets the symptoms of a stroke such as a paralysis down one side of the body or problems with language but completely recovers within 24 hours) with times of stability. In Alzheimer's disease the decline is consistent and gradual. In vascular dementia there would be signs of cerebrovascular disease - perhaps a history of a stroke or transient ischaemic attack, a history of having a heart attack, or the presence of risk factors for cerebrovascular disease (such as raised blood pressure, diabetes, raised cholesterol, atrial fibrillation, being overweight or smoking). These features of cerebrovascular disease, even if not already known, can be detecting by physical examination (by taking a measure of blood pressure or the pulse) or by detecting raised cholesterol or raised sugar (Indicative of diabetes) in a blood test.

A brain scan (either a CT or MRI scan) could reveal the presence of vascular changes in the brain - this can be either an area of stroke, where a wedge shaped area of the brain dies, or by changes to the brain called 'white matter' changes (the white matter indicating damage to the colourings of nerve fibres in the brain). There can also be a combination of the two.  

In someone with Alzheimer's disease, one might see particular shrinkage of the temporal lobe of the brain (the area associated with the preservation of memory). Sometimes, an ultrasound examination of the main arteries which supply blood to the brain (the carotid arteries) can show if there is narrowing of arthrosclerotic plaques in the carotid arteries. A doctor will come to a decision about the type of dementia from which the patient is suffering by looking at all aspects of the history, examination and the results of investigations. A gradual onset of illness with no evidence of cerebrovascular disease will strongly favour Alzheimer's disease, while a history of stroke, associated with loss of memory, makes vascular dementia more likely, and the presence of intermittent confusion with signs of Parkinson's disease would likely lead to a diagnosis of Lewy body dementia.

If any abnormal physical illness is found, for example a urinary tract infection, it should be treated in their own right.

Examination of a person with suspected dementia

•Mental state examination Depression

• Depression
• Memory and associated features

•Physical examination

• Check for signs of a stroke
• Check for risk factors for a stroke

•Detailed tests of memory

(neuropsychological tests)

• Investigations

• Blood tests
• Brain scan
• Chest X-ray
• Electrocardiogram Electroencephalogram.

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