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Dementia is in a category of illness that we refer to as disorders of intellect. The two major disorders of intellect are dementia and mental retardation. There are a couple of other collateral problems that I am going to define for you. Intelligence is the ability to have ideas and to reason about these ideas. The underlying systems within the brain responsible for this are the so-called cognitive systems, or the cognitive functions of the brain. There are hundreds - some would argue thousands - of such systems and the only way to make much sense out of these is to divide them into spheres. I’ve found it useful to divide cognitive functions into four major spheres. I’m going to list them again because the examination of a patient with a disorder of cognitive function, or in fact any disorder of thinking, should involve testing.
Let me define dementia carefully. This is where the slight difference of opinion comes in between us neurologists and psychiatrists in the form of the DSM IV. Dementia to me is a usually, usually but not always, progressive loss of intellectual function which was once there. I don’t accept the idea that dementia must be progressive because in my world, working at a big general hospital, many of the dementias that I see are not progressive. Can you name two important causes of illnesses which take away intellectual capacity but which do not progress? Two important major categories of illness. One, which you see a lot of, one which I see a lot of. One is head trauma, of course. Head trauma can take away intellectual capacity. It can leave people with a dementia which does not progress. And two? Cardiac surgery or other extracorporeal circulation leading to a loss of intellectual capacity in a large number of people. Probably as many as one-third of people who undergo extracorporeal circulation have lost intellectual capacity which never returns. But also does not worsen. Nonetheless, this can take away people’s work, it can change their lives. It is a kind of dementia. Not all dementia is progressive. It just happens that among the elderly the most common diseases which lead to dementia happen to be inherently progressive illnesses. The most famous and important of which is Alzheimer’s disease. But even if you take multi-infarct dementia that’s a disease which most of the time actually progresses. It’s difficult to stem the progression of ischemic stroke even though we try. So most dementias do progress but they do not all progress. So I call dementia "a usually non-progressive illness, characterized by loss of intellectual capacity which was once there." That distinguishes it from mental retardation, which is a failure to develop what should have been normal intellectual capacity for that individual. The two are not mutually exclusive, as I told you. Down’s syndrome being a case in point.
A pseudodementia is defined as any disorder of affect, mood, or thought which interferes with our testing of intellectual functions. And sometimes with people’s function such that it appears as if they have a dementia. What’s the most common cause … let me warn you before I say this, because this the kind of a board question. I see this on the boards over and over again. I’m going to ask you a trick question. What’s the most common cause of pseudodementia? So you couldn’t resist, could you? Even though I told you it was a trick question, I said I am going to give you a trick question. You still couldn’t resist. Your reaction time is so fast. Everybody is saying depression, of course. Who told you that? Where did you learn … think back in your memory. Where did you learn that in a population of 1000 consecutive dementia patients that depression is the most common pseudodementia? That is a disorder of affect, mood and thought, interfering with intellectual function but not Alzheimer’s disease or multi-infarct dementia.
Lastly, benign senescent forgetfulness is the worry about dementia. This is the downside of the fact that society has become cognizant of dementia. Now we have a new disease, that people were worried about getting dementia. In my practice this is extremely common. The middle-aged stockbroker who says he is losing his mind. "I’m losing my mind. I can’t find my keys. I went to the airport the other day. I left my car somewhere. When I came back the next day I couldn’t find my car. I went up and down and then I couldn’t find my keys and then I couldn’t think of my client’s name. I tried to introduce him to my wife. I couldn’t think of the guy’s name. It was very embarrassing. I’m losing my mind." That’s the history. "What do you think it is?" "I think it’s Alzheimer’s disease. I’ve been reading all about it. My great-aunt Sadie at the age of 98 was in a nursing home. She was incontinent and I think she must have had it, I think I have it. I want to take estrogen therapy, I want to do exercise therapy." This is a very common problem. I turned to a guy like that recently and said, "You know something? You know more about dementia than my residents know about dementia. You can’t have dementia and know more about dementia than my residents at the same time." As I tell my residents and I tell my students, "There are lots of things to worry about these days in medicine. A lot of things. There’s HIV, there’s drug-resistant tuberculosis, there’s ALS, there’s managed care, there’s a lot of bad things. There’s one thing you don’t have to worry about. That’s dementia.
Give them more names, make everybody fail and then tell them that they are pre-Alzheimer’s and give then vitamin E. Then repeat the test two weeks later. And turn the rheostat down. Now they are better. The vitamin E worked, didn’t it? It’s a scam.
What should you do in your office? My advice to you is to do a four-part mental status exam. Testing for attention, language, memory, and visual-spatial skills. My advice to you is not to mindlessly give the mini-mental or the seven minute battery or any other mindless battery, and certainly not have somebody else give the test and put some number in the record. Not good enough. If you really want to pick up anything and help you. What is the four-part test? Test everybody’s attention who complains of anything wrong with their thinking or whose family complains about their thinking. That means, are they able to maintain a coherent stream of thought or action. This is one of the most important sub-systems of the human nervous system. The ability to focus on one subject while holding other subjects at bay. We are doing this all the time. It is probably a subcortical function done
That’s what limbic valence is all about. When that system is not working, imagine what life would be like. All sensory information, unfiltered by the thalamus, takes on equal importance. Your wristwatch on your wrist, your bladder filling up, my words, your thoughts, the person next to you breathing, the air conditioning system, all taking on equal importance. Could you function? Impossible. This state is called inattention or confusion. The inability to maintain a coherent stream of thought or action. That is the most common pseudodementia by far. Certainly at a general hospital or a
Now there are many causes of dementia, but the most important one I don’t want you leave here without knowing something about, is an update on Alzheimer’s disease. The importance of course is that Alzheimer’s disease is the most common of the true dementias. We are now excluding all pseudodementia. That is, all confusional states, all delirium, all depressions, all schizophrenia, all of the non-dementia illnesses. What we are left with is a group of diseases, the most common of which by far is Alzheimer’s disease. It is becoming clear as we learn more and more about this that much of what we used to call multi-infarct dementia is really Alzheimer’s too. I think that multi-infarct dementia has seen its better days. They are behind it. There isn’t that much multi-infarct dementia. It has been over-diagnosed. Just because people got multi-infarcts doesn’t mean they have multi-infarct dementia. It’s very very difficult to be certain that the infarcts are the cause of the dementia. Now that we have more biological markers with AD, Alzheimer’s disease, it’s pretty clear that many people who were said to have multi-infarct dementia actually have AD. AD is much more common, and there is now emerging, pretty clearly, a unifying hypothesis for understanding not only AD but a number of underlying illnesses. Not only in dementia but outside of dementia in the field of movement disorders and elsewhere. AD has been an extremely fruitful bed of clinical pathological research. This is the key lesion, this is a CL plaque with a core of amyloid in the middle of it. This is the neurofibrillary tangle. We now know that the underlying protein abnormalities in these two structures are somewhat different. This is the so-called TAU protein. We now know there are a group of diseases which are characterized by the accumulation of the TAU protein. Among them are almost certainly what used to be called Pick’s disease and what is now called frontotemporal dementia. Another disease called progressive primary aphasia. Those are probably all TAU diseases. This leads us to a much more common illness, the disease in which the major pathology is the development of these senile plaques. More than the number you would normally see in aging, in a very characteristic geography in the brain. Alzheimer himself, Alois Alzheimer, when he described the disease which he said "Spared the soma, ravaged the mind and spared the soma" knew himself that there were plaques and tangles in the brains of people who died of this disease. What he did not know was that there was also amyloid, this pink substance in the wall of the vessels and this amyloid turned out to be central to the understanding of all of the aspects of Alzheimer’s and its related diseases. When this was first noted years ago by a neuropathologist, who said that he thought amyloid was not there accidentally but might be pathogenetic Alzheimer’s disease, people thought that this was a completely crazy idea. They said, "That’s outrageous. Amyloid is a secondary substance. There are many systemic amyloidoses which don’t cause any brain disease, therefore this cannot be a amyloidosis." I guess it’s pretty clear, that everybody in this room now knows that that is not true. It is working out that this disease is a cerebral amyloidosis.