Dementia is a condition in which a person is losing, or has lost, cognitive abilities. Although Alzheimer’s Disease (AD) accounts for 50 -70 % of all cases of dementia there are several possible reasons why a person might be suffering from dementia. Some are treatable, some are not. Therefore, all cases of dementia need a careful evaluation.
Just like our bodies change with age so does our brain. Some begin very early, while others occur later. Reaction times, for example (the time it takes to react to a stimulus), begins to slow in our late teens and early twenties and continues to slowly decline with age. This is one reason most top athletes, for example tennis players, peak at such a young age.
All of us, at one time or another, have blocked on recalling a well known word or name. We know what it is, but just can’t bring it to our consciousness even though we may even know the first letter of its spelling. Psychologist call this the tip of the tongue phenomenon (http://en.wikipedia.org/wiki/Tip_of_the_tongue ). Throughout our lives this happens to all of us, but its occurrence seems to increase as we pass from the late 50s to early 60s.
Regardless of age, any decline in cognitive abilities in the form of memory loss and confusion can be a sign that brain cells are failing. There may be many reasons for brain cells to fail. Most commonly, it’s from not enough oxygen and nutrients flowing to brain areas. Because some of these causes can be reversible, anyone who shows signs of dementia should be evaluated. A thorough work-up begins with the doctor taking a careful history – is there a family history of dementia? How rapidly is the onset of symptoms? Are there signs of depression? (Severe depression can appear similar to dementia.) Chronic drug or alcohol abuse can also cause symptoms that mimic dementia. An evaluation should include complete blood studies to look for treatable abnormalities, such as Vitamin B12 deficiency. Finally, imaging studies (discussed in a previous blog) can document some causes, such as a brain tumor. If all the studies are negative, the imaging may show signs of brain shrinkage do to loss of cells. The diagnosis of AD or any other type of dementia is made only by putting all this information together and is not based just on the imaging studies alone. If no other cause for dementia is determined, then it’s likely due to AD.
A German physician, Alois Alzheimer, first described it in 1906. If we look microscopically at the brains from AD patients we see two abnormal structures – plaques and tangles. Plaques are deposits of a protein fragment called beta-amyloid. Tangles are twisted fibers of another protein called tau (rhymes with “wow”).
In the process of aging, everyone develops some plaques and tangles. But people with AD have many more than would be normal, especially in areas that are important for learning and memory.
Plaques and tangles are thought to block communication among nerve cells and are the equivalent of nerve cell tombstones left over from dead cells. The build up of amyloid in cells may be the result of a malfunction of the cell’s ability to produce and use energy (a function of the mitochondria). Preventing or slowing this build up is likely to be where future treatment will be effective.
Until recently no drugs were available to treat AD, but Aricept®, a recently released drug, appears to slow symptom progression. Unfortunately, it does not reverse the damage that took place before the starting treatment.