Heterogeneity and prognosis in dementia of the Alzheimer type.

The diagnosis of dementia of the Alzheimer type (DAT) depends on the clinician's ability to document intellectual impainnent in the patient and to exclude other causes of dementia. About 50% of all demented patients entering a hospital are ultimately found at postmortem examination to have Alzheimer's disease. However, using the most rigorous criteria the accuracy of correct clinical diagnosis at autopsy approaches only 80-90% and this excludes some unusual patients. Most investigators use the Diagnostic and Statistical Manual of Mental Disorder-third ed. (DSM-III) criteria for dementia, a rating of perfonnance in activities of daily living, and an assessment of personality and intellectual function for diagnosis. Two clinical rating scales: the Blessed Dementia Rating Scale (parts 1 and 2) and the Clinical Dementia Rating Scale, are used frequently and seem to identify patients with DAT with greater accuracy than other scales. Our assessment protocol for dementia includes a quantitative neurological examination because certain motor manifestations have been observed in DAT: myoclonus, rigidity, stooped posture, and bradykinesia. We found these clinical features to be useful in predicting the course in some patients. Our data indicate clinical heterogeneity in DAT and may suggest the presence of unique subgroups.