Alzheimer-type senile dementia is associated with behavioral signs and symptoms that divide into corresponding stages. In the early stage, subjective memory deficit may be difficult to differentiate from benign senile forgetfulness. However, elderly persons with benign forgetfulness are unable to recall unimportant details, whereas patients with Alzheimer-type senile dementia forget important and unimportant information randomly (Krai 1962).
Typically, patients with Alzheimer's disease forget where things are placed, become lost easily, and have difficulty remembering appointments. Both recent and remote memory are affected, which may be documented by neuropsychological testing. When patients recognize their cognitive and social losses, many develop feelings of hopelessness and despondency. As Alzheimer-type senile dementia progresses, the patient enters a confusional phase with more global impairment of cognitive functioning (Schenk, Reisberg, and Ferris 1982). Changes in higher cortical functions, such as language, spatial relationships, and problem solving, become more apparent.
During the confusional phase, obvious denial begins to replace anxiety, and cognitive deficits are noticeable to family and friends. In the final phase, the patient becomes aimless and may hallucinate or be restless and agitated. Language disorders such as aphasia occur in late stages. Abnormal neurological reflexes, indicative of loss of higher neural inhibition, are common. Not all patients with Alzheimer-type senile dementia demonstrate the classic evolution of symptoms. Although almost all patients have some memory impairment, other focal cortical defi cits may predominate initially. Spatial relationship impairment is common early. The patient may also complain of word-finding difficulty or demonstrate mild problems in speaking and understanding. In cases where damage to the frontal lobes of the brain predominates, the patient presents with judgment problems.
Diagnosis of Alzheimer's disease remains a diagnosis of exclusion. In the absence of biological markers for the illness, it is not surprising that clinical diagnosis may be less than accurate and, in fact, may be correct in as few as one-half of Alzheimer-type senile dementia cases (Alafuzoff et al. 1987). Not only do cognitive changes associated with normal aging overlap those found in the early stages of dementia, but also a wide spectrum of conditions may produce dementia. In any given patient, several conditions leading to progressive cognitive decline may occur simultaneously. Even neuropathologists may encounter diagnostic difficulty and may be reluctant to make the diagnosis without the proper clinicopathological correlation (Khachaturian 1985).
The clinical diagnosis of Alzheimer-type senile dementia always requires documentation of progression (McKhann et al. 1984). Reports from family and friends provide the most valid measures of cognitive decline in elderly persons and support the clinician's judgment that global intellectual deterioration has occurred.
Progression is usually gradual but with fluctuation of symptom severity. The patient may react very dramatically to changes in the living situation, to losses of friends or relatives, or even to admission to the hospital for evaluation. These acute changes probably represent withdrawal of orienting stimuli and emotional distress rather than progression of the disease process.
A number of clinical staging strategies have been developed, but there is no entirely satisfactory technique as yet. Simplified rating scales (such as the Folstein Mini-Mental) may be efficiently administered, but only identify the presence or absence of cognitive impairment. Other cognitive scales are more accurate, but they are also more complex and may take an hour to administer. The Blessed Scale (Blessed, Tomlinson, and Roth 1968) obtains information from collateral sources and has the advantage of documented correlation with pathological lesions at autopsy. Unfortunately, it provides little information about cognitive performance. Other behavioral scales rely solely on the interviewer's interpretation of the patient's performance on several activities (Salzman, Kochansky, and Shader 1972).
Psychometric tests may be useful in delineating patterns of cognitive deficit at various stages of severity and in identifying the qualitative aspects of performance deficit. Although laboratory tests are sometimes used to support the diagnosis of Alzheimer's disease, the laboratory is actually more useful in excluding other causes of cognitive deterioration. Atrophy of the cerebral cortex is often seen on computed tomography, but it is frequently overinterpreted. There is a poor correlation between size of the brain ventricles, widened cerebral sulci, and severity of dementia (Fox, Topel, and Huckman 1975). Attempts have been made to correlate dementia with brain density (Albert et al. 1984). Unfortunately, results have been inconsistent, and there is a pressing need for quantitative computed tomographic studies that correlate the scanning images with clinical and pathological findings.
Alzheimer's disease may be difficult to distinguish from other untreatable progressive dementias, which include Pick's disease, demyelinating diseases, slowly progressive brain tumors, inflammatory diseases, arteriosclerotic vascular diseases, toxic exposures, repeated metabolic insults, deficiency diseases, late sequelae of head trauma, Creutzfeldt-Jakob disease, and viral and fungal infections. Dementia is common in patients with terminal cancer and may result from a variety of causes.
The evaluation of a patient presenting with dementia often reveals untreatable causes, but treatable dementia is discovered in 20 to 25 percent of such patients (Wells 1977).
Treatable causes of dementia include pernicious anemia, thyroid disorders, chronic central nervous system infections, toxic exposures, surgically correctable mass lesions, inflammatory vascular disease, certain forms of arteriosclerotic vascular disease, and normal-pressure hydrocephalus. Occasionally, iatrogenic dementia, related to the inappropriate use of medication or to idiosyncratic drug effects, is identified. Multi-infarct dementia may be the most difficult progressive dementia to differentiate from Alzheimer's disease despite the fact that specific diagnostic criteria for each have been promulgated in the official nomenclature. There is an obvious need for a valid and reliable set of clinical criteria to distinguish the two conditions. Nonetheless, risk fac tors for stroke should be evaluated and controlled when possible in every patient with early dementia.
J. L. Cummings and D. F. Benson (1983) suggest that all forms of dementia other than Alzheimer's and Pick's disease show signs of subcortical dysfunction in addition to more obvious cortical signs. This is especially true of dementia associated with basal ganglia disease, which regularly produces the characteristic subcortical pattern of slowed thinking, attention deficit, memory impairment, and apathy. Subcortical dementia occurs in 20 to 40 percent of patients with Parkinson's disease (Marttila and Rinne 1976) and is also observed in progressive supranuclear palsy, Huntington's chorea, and Wilson's disease. Symptomatic treatment of basal ganglia disease occasionally improves the associated dementia. Antidepressants may improve cognition as well as any associated depression (Albert, Feldman, and Willis 1974).
Depression is the most common treatable illness that may masquerade as Alzheimer-type senile dementia. Cognitive abilities return to baseline levels when depression is treated. Because some patients with early dementia have secondary depression, dementia and pseudodementia may be difficult to differentiate. The depression that occurs in the early stages of Alzheimer-type senile dementia tends to resolve as the disease progresses. Pseudodemented, depressed patients are apt to have poor attention, inconsistent cognitive changes, absence of cortical signs, weight loss, sleep disturbance, guilt, poor self-esteem, a past personal family psychiatric history, and a more rapid onset.
In contrast, patients with cortical dementia of Alzheimer-type often show insidious onset, slow progression, early loss of insight, amnesia for remote and recent events, spatial disorientation, reduction in spontaneous speech, and occasionally aphasia. Agnosia, apraxia, increased muscular tension, and abnormal neurological reflexes may also be present (Gustafson and Nilsson 1982).
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