Dementia means deterioration in intellectual capacity. The condition is distinguished from mental retardation, in which subnormal intellectual ability has been lifelong and may or may not be caused by brain injury; and from aphasia and Korsakoff’s psychosis, in which specific intellectual skills (language and memory, respectively) have deteriorated without a proportional disturbance in other cognitive functions.
Dementia is a clinical entity.
Any pathologic process affecting the cerebral hemispheres can lead to an impairment in intellectual capacity. The extent of the brain injury and not the location of injury or the nature of the neuropathology determines its severity. The diagnostic task is twofold: first, the physician must recognize the symptoms of dementia; then, he must identify the cerebral pathology producing it. The first aspect of diagnosis requires skill in testing mental function; the second, knowledge of the mode of onset of different pathologic conditions and of the associated neurologic signs and laboratory data.
The earliest symptoms of dementia can pass almost unrecognized. They may be merely a slight loss of mental quickness, spontaneity, and initiative. Symptoms are hard to differentiate from fatigue or boredom. The patient is vaguely changed. He has lost his sparkle, and seems slow and lacking in energy. It is usually a close family member who first recognizes the changes. But as the dementia progresses, symptoms become obvious to all. Difficulties in recent memory are often the first tangible symptom. The patient can’t remember immediate happenings, although his remote memories remain. He overlooks appointments, forgets a recent conversation, becomes lost in familiar surroundings. Also, it becomes difficult for him to think through new tasks, and he cannot comprehend complex commands. He fails to follow the gist of conversations or to interpret the activities of other people correctly.
His judgment is poor, and decisions are difficult. Language may be employed with less direction, pertinence, and nimbleness as the patient falls on cliches and habitual observations rather than choosing words with imagination and precision. At this time in the progress of a dementing illness a patient may maintain a facade of normality by comporting himself with his customary manners and employing his habitual modes of speech. But his social stance merely covers over his analytic and integrative failings, which are revealed when conversation or inquiry is carried beyond the stage of casual interchanges.
The demented patient may suffer also from depression, anxiety, or easy irritability. These symptoms may be the outcome of the difficulty he .appreciates in accomplishing tasks that were previously easy, or may represent changes in emotional control owing to injury to significant cerebral tissue.
Finally, with worsening, the patient can lose all his mental efficiency. His behavior deteriorates badly as he fails to care for himself or appreciate his surroundings. He loses his remote memories, now failing to recognize his closest relatives. He eventually cannot care for himself, and becomes bedridden and totally unaware of his surroundings. At this time his duration of life is dependent upon the nursing care he receives.
Dementia, thus, is a decline in all intellectual functions, and is reflected in every aspect of behavior.
Diagnosis of Dementia And Criteria of Dementia Diagnosis
It is not difficult to recognize intellectual impairment in individuals late in the course of a cerebral disease. The more taxing problem is the recognition of the intellectual impairment when it is slight and potentially reversible. The tests of cognitive function that are part of the neurologic examination of every patient are intended to accomplish this. But they must be interpreted with care.
It is customary to test (1) orientation to time, place, and person; (2) language skills, by naming common objects and comprehending commands; (3) fund of knowledge, such as the names of some capital cities and of presidents; (4) recent memory, by setting three objects to be remembered for 5, 10, and 30 minutes; (5) attention span, by asking for a serial subtraction of 7 from 100 or any other arithmetic task that requires “carrying over”; (6) abstract reasoning power, by asking for definitions of proverbs or the similarity of words such as apple-orange, ear-eye, poem-statue; and (7) constructional capacity, by asking the patient to draw simple objects such as a clock or to copy an abstract design.
The results of these tests must be interpreted in the light of other knowledge about the patient. If the patient was a gifted professional person whose family has noted a decline in his judgment and an increasing forgetfulness, the discovery that he cannot hold three names in mind for five minutes and that he interprets proverbs clumsily provides some evidence that he is suffering from a disturbance to his intellectual power. On the other hand, if the patient was not a person with intellectual achievements in the past and has received a poor education, difficulties in proverb interpretation or fund of knowledge are less likely to represent brain disease.
Although it is possible to find all the intellectual functions disturbed in dementia, the tests for recent memory, for attention, and for constructional capacity are most useful. Deficiencies here are easy to document; these functions are affected early in the course of many brain diseases and they are little dependent on education. Also, tests for recent memory are useful in differentiating a patient with mental retardation from an individual of limited intelligence who is developing a brain disease, since memory function is intact in the mildly retarded individual.
It is important to differentiate Korsakoff’s syndrome and aphasia. The patient with Korsakoff’s syndrome will fail the tests of recent memory. He will be disoriented to time and place, but he will be able to name objects, obey commands, and accomplish tasks of abstract reasoning and drawing if he can hold the question in mind. His disorder is in memory. The rest of his intellectual function is relatively spared. The aphasic patient will have severe problems in naming objects and comprehending words. But if this difficulty can be surmounted, it will be evident that it is language specifically that is disturbed, and other mental functions such as memory, orientation, and the capacity to draw are relatively intact.It is often useful to supplement the bedside tests of mental function with standardized examination of intellectual skills. The Wechsler Adult Intelligence Scale (WAIS) is most often employed. Nothing about this psychologic examination is different in concept from the bedside tests. It measures the intellectual performance of a patient by asking him to attempt problems in several different areas.
Since a mathematical score is given, it is possible to compare his performance with other individuals objectively. Although the WAIS includes problems similar to those gwen’s at the bedside, it adds several “performance” tests which are actually unfamiliar tasks, such as recognition of errors in pictures, design of patterns from colored blocks, and assembly of parts of puzzles. These tests most specifically examine the ability of a patient to put his mind to an unfamiliar situation and solve it. They are less dependent on learning and in fact decline early in a dementia and so produce a discrepancy between these “performance scores” and the “verbal scores” which tend to remain intact for a longer period.
Diagnostic Issues in Dementia.
As mentioned in the introduction, the symptoms of dementia appear with an injury to the cerebral hemispheres, and are not specific for a particular pathology. It is the course of their development, the associated neurologic signs, and the laboratory findings that permit diagnosis of the pathologic entities producing the dementia.
Since the same symptoms can be produced by curable, reversible pathology as by incurable and progressive disorders, the first diagnostic consideration should reflect a search for the treatable pathologic entities. Each of the following conditions should be considered in every patient with the symptoms of dementia: general paresis, myxedema, neoplasms and other chronic intracerebral lesions, hepatolenticular degeneration (Wilson’s disease), avitaminosis Bi2, folic acid deficiency, and occult hydrocephalus. Many of these conditions can be diagnosed by evidence derived from the clinical examination; others demand clinical laboratory studies. Thus the Argyll Robinson pupil of cerebral syphilis, lateralized motor-sensory signs of neoplasm, the Kayser- Fleischer ring of Wilson’s disease, and a gait disorder caused by a spastic weakness of legs in hydrocephalus should all be sought in the physical examination of the demented patient. A group of laboratory tests are required in the diagnostic evaluation. As a routine, all patients should have a lumbar puncture to measure intracerebral pressure and to obtain a sample of cerebrospinal fluid for analysis. Cell count, protein content, and a test for the syphilitic precipitants will be needed in cerebrospinal fluid. An analysis of gastric contents for acidity is required to exclude B12 deficiency. Blood serologic examination and analysis for protein-bound iodine are also indicated. An electroencephalogram is useful, as it may reveal a local lesion or a severe generalized slowing of the rhythms characteristic of intoxication. Skull roentgenograms can also reveal a local lesion. In many patients it is necessary to proceed to a pneumoencephalogram in order to exclude some of the rarer but curable forms of dementia such as occult hydrocephalus.
The onset and course of a dementing disorder must be carefully analyzed when considering the likely pathologic entities. Particularly, has the decline been acute (a week or less), subacute (a week to eight weeks), or chronic (more than two months)? Was the onset abrupt or insidious, was the subsequent course a gradual and relentless loss of mental faculties, or was it a series of sudden losses producing a steplike decline in the mental faculties? Different pathologic entities produce different clinical histories in these respects. Thus the dementia associated with vascular disease of the brain will have a sudden onset and increase in an intermittent and variable fashion. The dementia of gt ieral paresis tends to be subacute and steadily progressive; that of degenerative disease is more insidious in onset and slow in development.
The characteristics of four known cerebral degenerations will be reviewed as they exemplify some of these general statements about dementia. These conditions are Alzheimer’s disease, Pick’s disease, Creutzfeldt-Jakob disease, and Huntington’s chorea.