DIAGNOSING ALZHEIMER'S DISEASE

Dr. Alois Alzheimer (findagrave.com)

As we continue to look for a cure for Alzheimer's Disease, an interesting point must not be overlooked. The way we definitively diagnose the disease has not changed in 100 years since Dr. Alzheimer discovered the disease under the microscope.
To arrive at the definitive diagnosis of AD, brain tissue must be examined at the microscopic level. This can be done with a brain biopsy, (taking a piece of brain tissue and examining it) which is obviously not done in a living human being. The brain can't handle a biopsy, unlike say the liver or skin, or secondly an autopsy when the person dies, in which the brain tissue can be examined microscopically.
Other than that, the diagnosis still remains one essentially of exclusion. That is: you rule out other causes of dementia.
So how is it diagnosed with 80-90% accuracy in a living human being? Lab tests, ruling out things like thyroid problems, vitamin B-12 deficiency, syphilis, etc. Then imaging, CT scan, MRI, to look for other structural changes, e.g. brain tumor, vascular or blood vessel disease, you can see small strokes, (infarcts) on imaging, where the blood circulation of the brain was compromised. Sometimes an EEG electroencephalogram is done, that is generally to look for seizure focus (that is the test where they hook up all the wires to the head, and monitor the brain waves)
The first and foremost thing is that a very, very careful and in depth history must be done, (before the tests). Information from the patient, family members must be gathered. The more information the better. There of course are many commonalities in the history and onset of AD.
After the history, a thorough exam is done, (or should be done) This includes a physical, (often at the level of primary care, to rule out other medical problems that may be compromising ones mental functioning, and a THOROUGH neurological exam, testing ones sensory and motor function and a THOROUGH mental status exam. Testing one's short, intermediate and long term memory, concentration, attention, orientation etc.
In addition a THOROUGH psychiatric history should be done. Depression for example can mimic certain findings in AD. Complicating the picture more is that depression can co-exist with AD, and can be a presenting sign. Sometimes the depression gets picked up but the dementia missed, and vice versa. Of course there is the usual stigma and bias in society towards mental health, so this part can often be overlooked till it is of severe proportions. (bias and preconception and skewed views about mental health even exist in the health care field outside of psychiatry)
Another problem we forget about a lot is that AD can (and often does) co-exist with other problems such as Vascular or multi-infarct dementia (blood vessel disease and problems with circulation to the brain)
Despite the findings and research into causes, genetics, environment, etc, and all the clinical expertise and AD specialty centers, in the end that is still how you definitively diagnose the disease, just like Dr. Alzheimer did 100 years ago.
As we continue to look for THE CAUSE, THE GENE, we must consider this fact: Like many other problems such as heart disease, there may be many contributing factors and not just ONE CAUSE or ONE illusive gene.