Progressive aphasia: a precursor of global dementia?

We studied 8 subjects longitudinally in whom isolated language dysfunction had developed gradually at a mean age of 62.8 years. The language deficits initially displayed by the subjects were characteristic of the syndrome of "progressive aphasia without dementia." By 5 years after onset of progressive aphasia, however, 7 of the 8 subjects additionally had developed mild dementia as diagnosed by clinical means, and the remaining subject demonstrated declining performance in both verbal and nonverbal psychometric measures. Thus, generalized cognitive impairment occurred in all. Neuropathologic evidence of a diffuse dementing disorder was present in the 2 subjects studied postmortem. One had Alzheimer's disease with disproportionate involvement of the left inferior parietal cortex, and the other displayed widespread neocortical neuronal loss and microvacuolation in the absence of specific histopathologic markers. In this series, progressive aphasia was a precursor of global dementia.