Heterogeneity in dementia of the Alzheimer type: evidence of subgroups.

We reviewed records of 121 consecutive patients with dementia of the Alzheimer type. Patients with myoclonus or extrapyramidal signs had greater intellectual decline and functional impairment in daily activities. Among patients studied over 4 years, there were four groups: benign--little to no progression; myoclonic--severe intellectual decline and frequent mutism after younger onset; extrapyramidal--severe intellectual and functional decline and frequent psychotic symptoms; typical--a gradual progression of intellectual and functional decline, but without other distinguishing features. Except for the group with myoclonus, no subgroup was segregated by age at onset or other demographic variables. This study suggests that dementia of the Alzheimer type is heterogeneous, and that certain clinical manifestations may be useful in predicting outcome.