Differences in aphasia syndromes between progressive supranuclear palsy-Richardson's syndrome, behavioral variant frontotemporal dementia and Alzheimer's dementia

Language impairments, hallmarks of speech/language variant progressive supranuclear palsy, also occur in Richardson's syndrome (PSP-RS). Impaired communication may interfere with daily activities. Therefore, assessment of language functions is crucial. It is uncertain whether the Aachen Aphasia Test (AAT) is practicable in PSP-RS, behavioral variant frontotemporal dementia (bvFTD) and Alzheimer's dementia (AD) and language deficits differ in these disorders. 28 PSP-RS, 24 AD, and 24 bvFTD patients were investigated using the AAT and the CERAD-Plus battery. 16-25% of all patients failed in AAT subtests for various reasons. The AAT syndrome algorithm diagnosed amnestic aphasia in 5 (23%) PSP-RS, 7 (36%) bvFTD and 6 (30%) AD patients, Broca aphasia in 1 PSP-RS and 1 bvFTD patient, Wernicke aphasia in 1 bvFTD and 3 (15%) AD patients. However, aphasic symptoms resembled non-fluent primary progressive aphasia in 14 PSP-RS patients. In up to 46% of PSP-RS patients, 61% of bvFTD and 64% of AD patients significant impairments were found in the AAT subtests spontaneous speech, written language, naming, language repetition, language comprehension and the Token subtest. The CERAD-Plus subtest semantic fluency revealed significant impairment in 81% of PSP-RS, 61% of bvFTD, 44% of AD patients, the phonemic fluency subtest in 31, 40 and 31%, respectively. In contrast to bvFTD and AD, severity of language impairment did not correlate with cognitive decline in PSP-RS. In summary, the patterns of aphasia differ between the diagnoses. Local frontal language networks might be impaired in PSP-RS, whereas in AD and bvFTD, more widespread neuropathology might underly language impairment.

Atypical clinical features associated with mixed pathology in a case of non-fluent variant primary progressive aphasia

A 66-year-old woman presented with agrammatism and apraxia of speech, meeting criteria for non-fluent/agrammatic variant primary progressive aphasia (nfvPPA). However, three years later, she developed frontal/executive, short-term phonological memory, visuospatial, and visual memory deficits suggesting involvement of multiple brain networks. Multimodal neuroimaging showed damage of both fronto-striatal and posterior brain regions. She was found to have multiple pathological processes: corticobasal degeneration (CBD), Alzheimer's disease (AD), and TAR DNA-binding protein (TDP)-43 type A. We hypothesize that cognitive and neuroimaging findings consistent with damage to multiple brain networks, each associated with vulnerability to certain molecular disease subtypes, could indicate mixed pathology.