NEUROPSYCHOLOGY UPDATE  - Alzheimer’s Part One

ALZHEIMER’S DEMENTIA

THE DEFNITION AND DIAGNOSIS OF ALZHEIMER’S

 Alzheimer’s Dementia is a great concern to most persons as they grow older.  Most of us know people who have succumbed to

this disease or have people in our family who have had Alzheimer’s.  The definition of Alzheimer’s, according to the Diagnostic and
 
Statistical Manual IV, is as follows: 

There must be evidence of a Memory Loss and there must be evidence of either: Anomia - which is word search, Agnosia - difficulty in recognizing visual objects, Ataxia - motor impairment not due to other known causes, and Executive Function -  losses in ability to plan ahead, etc. 

The diagnosis requires that both the memory loss and the secondary symptom cause significant impairment in daily function. The exact diagnosis of Alzheimer’s depends upon, first of all, clarifying the degree of memory loss and then, secondly, testing for and determining the presence of one of the other four significant symptoms. 

Any tests of these kinds require that you compare the person being tested with other people of his/her own age. The kinds of tests used are very important.  A test for dementia of any kind is only as good as the research studies that have been done on the validity of the tests.  The establishment of test validity is a rather complicated and demanding process and may take a number of years.  In other words, the 20-item questionnaire that you run across in a popular magazines will not give you definitive information on whether or not one has Alzheimer’s. Again, the testing depends upon using tests that are well validated, that are reliable across time for patients, and which have good normative data available for the patient’s age group. 

RISK FACTORS FOR ALZHEIMER”S DEMENTIA

There are some risk factors for Alzheimer’s, among these, the most prominent is age.  The incidence of Alzheimer’s doubles every five years beginning at 60 years.  In other words, at age 60 the risk of Alzheimer’s is only about 2% by age 65, that is double to 4%, at age 70 to 8%, at age 75 to 16%, at age 80 to 32%, and by age 85 the frequency of Alzheimer’s has gone up to 40% or 50%.  In other words, from being a disease which occurs rarely among persons who are 60 years old, it increases so that by the age of 85 the incidence is almost one half.  In a group of 10 people age 85 or older, 5 of them may have Alzheimer’s.

There are other things which appear to contribute to the risk for Alzheimer’s.  There is the less significant contributions of being of female gender, and/or a history of brain injuries.  One of the things of great concerns to many people are the genetic risk factors.  This is a risk which is present but perhaps not as severe as often believed.   If at least one apoE-4 allele is present the lifetime risk for that person to develop Alzheimer’s is 30%, while the normal risk is 10%.  However, that also means that 70% of persons with the apoE-4 will develop Alzheimer’s.  The triggers for the expression of the gene are not clear.

Overall, it has been estimated that 3% of Alzheimer’s is related to an autosomal dominant condition.  In the other 97% of cases there does appear to be an increased incidence in family members.  But this is not predictive. It is probably  worthwhile to know if there are members in your family that have had Alzheimer’s, and to be diligent in getting testing for yourself. 

The other very significant symptom of the diagnosis of Alzheimer’s is that the disease has a long and slow onset.  It is not uncommon to see persons with Alzheimer’s, who began having slippage in their memory five or six years before they actually came for neuropsychological testing. 

OTHER TYPES OF DEMENTIA

This long and slow onset is one of the most useful hallmarks of Alzheimer’s.  Other kinds of dementia are not characterized by this pattern.  For example, vascular dementia, related to the occurrence of a CVA or multiple CVAs, often will have a very sudden onset that is correlated with the occurrence of the CVA.  In this case, the person will be someone who has been functioning quite well and suddenly have an episode where they become very confused, disoriented, and may have symptoms such as double vision or difficulty with language, motor weakness, etc. 

In Lewy Body Dementia, the primary symptoms most are motor tremulousness similar to Parkinson’s, visual hallucinations (seeing things that are not there), and shift in attention concentration. Lewy Body Dementia, unfortunately, appears to progress much more rapidly than Alzheimer’s does. 

To simplify, it is certainly the case that all persons, as they grow older, begin to have “senior moments” and forget things.  They may have instances of word search when they cannot remember the name for a “stethoscope” when they are trying to describe their visit to the doctor, or they may forget the names of friends and acquaintances, etc.  The problem becomes to determine whether or not this forgetfulness and word search are beyond what one would expect for their age That is why specific testing is so important. 

Sometimes a diagnosis of “mild cognitive impairment” will be made. The data does not support a diagnosis of Alzheimer’s; repeat testing sometimes shows that Alzheimer’s is detected in later life. This picture of Alzheimer’s is also somewhat confounded by the fact people who are developing Alzheimer’s sometimes become depressed, and their depression may cause them to look more forgetful than they really are.  In some cases, depression may present symptoms that have some resemblance to early signs of dementia.

                Neuropsychological testing is still considered one of the best ways to assess Alzheimer’s. Complex brain scans (PET scans) are sometimes used to confirm diagnosis.