Predicting the reading profiles of different neurodegenerative impairments: The case of Alzheimer’s disease, Progressive Primary Aphasia and Posterior Cortical Atrophy

Objectives: We aimed at testing the reading performance in a sample of patients with neurodegenerative impairment.
Materials: We used two reading tasks of words and nonwords, and of words with unpredictable stress position, a repetition task of words and nonwords, and two lexical decision tasks (written and oral modalities).
Methods: We tested patients with Alzheimer's disease (AD, n=19), Primary Progressive Aphasia (PPA, n=6, three logopenic variants, one semantic variant and one pure anomic) and Posterior Cortical Atrophy (PCA, n=4). We also tested 34 healthy participants as a control group.
Results: In oral lexical decision AD patients had significantly lower performance than those with PCA, whereas the opposite pattern was found in written lexical decision. Reading of nonwords was more impaired than reading of words in both AD and PPA patients. Multiple single case analysis identified phonological dyslexia in 50% of PCA cases, in a much lower percentage in patients with AD (15.8%) and PPA (16.7%). In one AD patient the reading disorder was classified as surface dyslexia.
Discussion: No specific patterns of reading performance emerged as predictors of different neurodegenerative impairments. In general, in written lexical decision PCA patients show a worse performance as compared to that obtained in the other two groups. On the contrary, worse performance in the oral modality may orient towards a diagnosis of AD.
Conclusions: Various forms of neurodegenerative disease occur with different cognitive profiles, and reading processes are not an exception to this rule.
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