Alzheimer’s Disease is by far the most common cause of Dementia. The actual cause of Alzheimer’s is unknown, but it is known that there is an accumulation of an abnormal protein, called Beta Amyloid. The reason that this accumulation occurs is unknown. It deposits in formations called plaques and tangles, which may be in areas where nerve cells (neurons) have died. It is theorized that the abnormal buildup of this protein may damage the neurons. A loss of neurons seems to cause the progressive cognitive loss seen in Alzheimer’s Disease. Early on, some of the neurons most affected are found in a part of the brain where neurons releasing the brain transmitter chemical acetylcholine are found. This is the basis for treatment of the symptoms of Alzheimer’s Disease with cholinesterase inhibitor-type drugs Treatment of Alzheimer's.

Alzheimer’s can occur at any age from 45 or older, but is increasingly common with increasing age. About 10% of patients above age 65 have Alzheimer’s, but more strikingly, about half of the patients at age 85 have Alzheimer’s Disease.

Alzheimer’s causes a steadily progressive loss of cognitive function in several areas. At present, the progression of the disease cannot be halted, although there is much research underway trying to find effective treatments. Patients with Alzheimer’s are often unaware of their deficits, or of the degree of their deficits.

The diagnosis of Alzheimer’s cannot be made with any imaging study (MRI, CT scan, PET scan) or laboratory test. Instead, the diagnosis of Dementia of the Alzheimer’s type is made by first diagnosing Dementia, and second, ruling out other causes of Dementia with imaging studies and lab testing. Following this procedure, the diagnosis of Alzheimer’s is quite reliable when compared with eventual autopsy results.