Alzheimer's Disease

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There are no laboratory tests available that will positively diagnose Alzheimer’s Disease. Currently, the only definite diagnosis of AD is to examine a section of the patient’s brain tissue under a microscope; this is rarely undertaken during life. Pathologists look for senile plaques and neurofibrillary tangles characteristic of AD. Since plaque and tangle formation is also seen in normal aging, the sample must be compared to a control sample (normal, non-AD brain tissue) from a person the same age as the patient.

Some studies have suggested that looking at changes in specific substances in cerebrospinal fluid (CSF), such as tau protein or amyloid-beta proteins could help to make a diagnosis or monitor treatment. More research is required to see if these techniques could be useful in routine care.

Doctors currently use a variety of tests and procedures to rule out other causes for dementia, such as anaemia, infection, disorders of the thyroid gland, vitamin B12 deficiency and mini-strokes, before diagnosing patients as having AD.

In some patients, magnetic resonance imaging (MRI) scans are used to look for evidence of trauma, tumours or stroke that could be causing dementia and to look for brain atrophy (shrinkage) that is typical but not diagnostic of Alzheimer’s Disease (it may also be seen in many other brain disorders).

When a patient presents with symptoms of dementia, the doctor will evaluate his or her personal and family history (preferably of several generations); perform a physical examination; determine the age of onset, and undertake neuropsychological tests to measure his or her memory, language skills, and other cognitive functions. These tests include the Mini-Mental State Examination and the Montreal Cognitive Assessment scores. They can be repeated at intervals to determine how rapidly the disease is progressing. A hallmark of Alzheimer's Disease is that its appearance is a subtle, progressive decline in function. If the onset of the patient’s problems is abrupt or happened in a step-wise fashion, then the cause is most likely something other than AD.

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