“Dementia of the Alzheimer type” is the official title of the disease that is at present being newly diagnosed in several hundred thousand people each year in the United States. It accounts for somewhere between 50 and 60 percent of all dementing illnesses in those over the age of sixty-five and strikes many others in their middle years. The American Psychiatric Association describes its onset as insidious, with a “generally progressive, deteriorating course, for which all other specific causes have been excluded by the history, physical examination and laboratory tests. The dementia involves a multifaceted loss of intellectual abilities, such as memory, judgment, abstract thought, and other higher cortical functions, and changes in personality and behavior.”
The dementia itself is defined as: “Loss of intellectual abilities enough to interfere with social or occupational functioning.” Behind the deceptively simple words lie centuries of uncertainty and of blurred definitions and categories.
References to what we now call senile dementia, and even legal decisions related to the condition, have appeared for thousands of years in the literary and historical records of Western civilization. Medical authors since antiquity have described it, and physicians gradually came to recognize that younger individuals as well as the old sometimes develop evidences of impaired judgment and memory, and general intellectual deficits of a progressive nature. The word
dementia
did not appear as a medical term, however, until 1801, when it was introduced by Philippe Pinel, who was at that time the senior physician at Le Salpêtrière, a Paris hospital in which several thousand incurable and chronically ill women shared facilities with hundreds of the sick and insane. Pinel has been called the father of the modern treatment of mental diseases, primarily for the accuracy of his descriptions and classifications of psychiatric syndromes, but also for introducing the heretofore-absent element of human kindness into the care of the institutionalized mentally ill, many of whom had previously been kept in chains. He called his novel principle the “moral treatment of insanity.”
Pinel systematized his concepts of mental illness in the 1801 book that has become one of the classic volumes in the annals of psychological medicine,
Traité médico-philosophique sur l’aliénation mentale
. In this text, he described a distinct psychiatric syndrome to which he gave the name
démence
(in English, “dementia”), defined as a kind of “incoherence” of the mental faculties. In one brief paragraph entitled “Specific Character of Dementia,” Pinel outlined a group of symptoms that will immediately be recognized by anyone who has cared for a patient with the form of it that is today called Alzheimer’s:
Rapid succession or uninterrupted alternation of isolated ideas, and evanescent and unconnected emotions [unconnected either to each other or to external real events]. Continually repeated acts of extravagance: complete forgetfulness of every previous state: diminished sensibility to external impressions: abolition of the faculty of judgement: perpetual activity.
Pinel could have been describing Philip Edward Whiting. The terms
incoherence
and
unconnected
are particularly appropriate, being so consistent with the disabled networks of brain cells, connections, and chemical transmitters of messages that are now recognized to be the fundamental findings of the disease. Pinel was able to distinguish the dementia he introduced from the commonly observed senility of advancing age.
To many clinicians,
incoherence
served as an excellent clinical synonym for
dementia
. In an 1835 publication entitled
A Treatise on Insanity
, James Prichard, a senior physician to England’s Bristol Infirmary, pointed out that patients go through a series of stages as the disease progresses, which he called “the several degrees of incoherence.” He recognized four such degrees: impaired memory, irrationality and loss of reasoning power, incomprehension, and finally the loss of instinctive and voluntary action. These observations are useful even today in charting the gradual deterioration of individual patients. Indeed, modern authors do write of several stages of illness, and they are very much the same as Prichard’s.
Philippe Pinel’s student and intellectual heir was a graduate of the thousand-year-old medical school at Montpellier—Jean Etienne Dominique Esquirol. The observations concerning
démence
in Esquirol’s 1838 work,
Des Maladies mentales
, have stood the test of time. Once these are studied, little further discussion of dementia’s symptoms is required for those who would acquaint themselves with its clinical course as we see it today. Of his patients, Esquirol said:
[They] have neither desires nor aversions; neither hatred nor tenderness. They entertain the most perfect indifference towards objects that were once most dear. They see their relatives and friends without pleasure, and leave them without regret. They are uneasy in consequence of the privations that are imposed upon them, and rejoice little at the pleasures which are procured for them. What is passing around them, no longer awakens interest; and the events of life are of little account, because they can connect themselves with no remembrances, nor any hope. Indifferent to everything, nothing affects them. . . . Notwithstanding, they are irascible, like all feeble beings, and those whose intellectual faculties are weak or limited. Their anger, however, is only of a moment’s duration. . . .
Almost all who have fallen in a state of dementia, have
some sort of ridiculous habit or passion
[Esquirol’s italics]. Some are constantly walking about, as if seeking something they do not find. The gait of others is slow and they walk with difficulty. Others still, pass days, months and years, seated in the same place, drawn up in bed, or extended upon the ground. This one is constantly writing, but his sentiments have no connection or coherency. Words succeed words. . . .
To this disturbance of the soundness of the understanding, are united the following symptoms. The face is pale, the eyes dull, and moistened with tears, the pupils dilated, the look uncertain, and the physiognomy without expression. The body is now emaciated and slender; and now loaded with flesh. . . . When paralysis complicates dementia, the paralytic symptoms are manifested successively. At first, articulation is embarrassed; shortly after, locomotion is executed with difficulty; and the arms are moved with pain. . . . He who is in a state of dementia imagines not, nor indulges in thought. He has few or no ideas. He neither wills nor determines, but yields; the brain being in a weakened state.
Like all the great French medical professors of his day, Esquirol personally performed autopsies on his patients when they died. In that day of microscopes too primitive for accuracy, he had to depend on gross appearances to make his observations. Nonetheless, the findings were striking:
The convolutions of the brain are atrophied, separated from one another, shallowed or flattened, compressed and small, especially in the frontal region. It is not uncommon, that one or two convolutions of the convexity of the brain are depressed, atrophied, and almost destroyed, and the empty space filled with serum.
Esquirol had thus identified an atrophy of the brain that explained the atrophy of the intellect. His observations were confirmed again and again by later investigators. Microscopic analysis, however, would have to await the studies of Alois Alzheimer.
Medical science underwent many profound changes in the seven decades between the contributions of Esquirol and those of Alzheimer, but none was more important than the development of high-resolution microscopes. Their skilled use of the new optical systems enabled scientists at German medical schools to make many of the great discoveries of the second half of the nineteenth century and the first decade of the twentieth. It was in the German tradition of meticulous microscopy that Alois Alzheimer undertook the study of dementia.
Alzheimer had begun his career primarily as a clinician interested in nervous and mental diseases, but he was well trained in laboratory methods. Already an authority on the clinical aspects of senile dementia, and beginning to be known for the clarity of his descriptions of microscopic pathology, he was invited to work at the University of Heidelberg in 1902 by Emil Kraepelin, a pioneer of experimental psychiatry. When Kraepelin was called to the University of Munich in the following year to take charge of a new clinic and research facility, he took the thirty-nine-year-old Alzheimer with him. Alzheimer’s skill with the use of newly developed tissue-staining techniques enabled him to identify the changes in cellular architecture that accompany syphilis, Huntington’s chorea, arteriosclerosis, and senility. Perhaps the most distinctive characteristic of Alzheimer’s work was his ability, based on his own experience with patients, to correlate microscopic postmortem findings with the symptoms exhibited before death by the unfortunate victims of these degenerative processes. Such correlations are the basic elements in tracing the cause and effect of pathophysiology.
In 1907, Alzheimer published a paper entitled “On a Distinctive Disease of the Cerebral Cortex,” reporting the case of a woman who had been admitted to the psychiatric hospital in November 1901. This is the first study of a patient in whom the eponymous sickness was recognized as a singular entity to be differentiated from all others. Except that the language is far more stark, we might just as well be reading Esquirol; except that Alzheimer does not specifically outline the boundaries of each of the “four degrees of incoherence,” we might just as well be reading Prichard. Alzheimer presented a fifty-one-year-old woman who had gone through the successive symptoms of jealousy, failure of memory, paranoia, loss of reasoning powers, incomprehension, stupor, and, finally, “After 4½ years of the disease, death occurred. At the end, the patient was completely stuporous; she lay in her bed with her legs drawn up under her, and in spite of all precautions she acquired bedsores.”
The description of the patient’s clinical course was not the reason Alzheimer reported her case. Such patients had been familiar to physicians even before Pinel and Esquirol, although the two French clinicians were the first to separate them into the new category of dementia. In fact, the term
presenile dementia
had been introduced long before Alzheimer, even as early as 1868, in order to differentiate those patients who were still in their middle years when afflicted. Nor did Alzheimer wish to content himself merely with describing yet another demented cortex that was obviously atrophic on simple inspection with the naked eye. His purpose in the 1907 paper was to tell of what he had found when he sectioned this woman’s brain, applied special stains to the thinly sliced segments, and examined them under the microscope.
Alzheimer had discovered that many of the cells of the cortex contained one or several hairlike fibrils, which in other cells merged into groups, of increasing density. At what appeared to be a somewhat later stage, the nucleus and indeed the entire cell disintegrated, leaving only a dense bundle of the fibrils in its place. Alzheimer considered the fact that the fibrils absorbed a different dye than did the normal cell to be evidence that the deposition of some pathological product of metabolism was the cause of the lethal outcome. Between one-quarter and one-third of his patient’s cortical cells either contained fibrils or had disappeared entirely.
In addition to the destructive processes in the cells, Alzheimer found numerous microscopic clumps or plaques scattered throughout the cortex, which resisted taking up the dye. In later years, these were shown to be composed of degenerated portions of the intercommunicating nerve extensions called axons, clustered around a core of the protein substance beta-amyloid. To this day, the invariable presence of so-called senile plaques and fibrillary tangles are the primary criteria upon which a microscopic diagnosis of Alzheimer’s disease is made.
It has been recognized, however, that neither the amyloid plaques nor the neurofibrillary tangles are found exclusively in Alzheimer’s. There is a variety of other chronic conditions of the human brain in which one or the other or both can be identified. Even in normal aging, at least a few of both types of structures appear, though hardly in the large quantities characteristic of Alzheimer’s. We will know a great deal more about the process of brain aging once the origins of the plaques and tangles of this disease have been discovered.
Alzheimer was wise enough to recognize that “we are apparently confronted with a distinctive disease process.” His mentor, Kraepelin, went one step further: Referring to the new entity in the eighth edition of his textbook in 1910, he christened it “Alzheimer’s disease.” Kraepelin seemed uncertain about the significance of the comparatively young age of Alzheimer’s patient, in view of the fact that her history was so similar to those of people who had previously been put into the category of senile dementia. He wrote, “The clinical significance of Alzheimer’s disease is still unclear. Although the anatomical findings suggest that this condition deals with an especially severe form of senile dementia, some circumstances speak against this; namely the fact that the disease may arise even at the end of the fifth decade. One would describe such cases at least in terms of senium praecox [precocious senility], if not preferably that this disease is more or less independent of age.” This uncertainty by a man whom many considered the high priest of organic psychiatry may have influenced later authors to attach more significance to Kraepelin’s use of the term
senium praecox
and to have overlooked his suggestion that “this disease is more or less independent of age.” Probably as a consequence of this misinterpretation, the notion that Alzheimer’s is a
presenile
dementia became fixed in medical nomenclature for more than half a century.