"Dementia unmasked": atypical, acute aphasic, presentations of neurodegenerative dementing disease.

Acute onset of aphasia is most commonly due to a cerebrovascular event in the territory of the dominant hemisphere middle cerebral artery. An isolated and slowly progressive aphasia may occasionally be the presenting feature of a dementia syndrome. The longitudinal clinical, neuropsychological and neuroimaging findings of two patients with an acute, perioperative, onset of aphasia are reported, to show that acute aphasia may on occasion be the presenting feature of neurodegenerative dementing disorders, notwithstanding clinical diagnostic exclusion criteria for these conditions.