Quantitative assessment of grammar in amyloid-negative logopenic aphasia.

Logopenic primary progressive aphasia (lvPPA) typically results from underlying Alzheimer's disease, but subjects have been reported that do not show beta-amyloid (Aß) deposition. These subjects do not differ on neurological and speech-language testing from Aß-positive lvPPA, but they impressionistically show increased grammatical deficits. We performed a quantitative linguistic analysis of grammatical characteristics in Aß-negative lvPPA compared to Aß-positive lvPPA and agrammatic PPA, which is characterized by increased grammatical difficulties. Aß-negative lvPPA used fewer function words and correct verbs but more syntactic and semantic errors compared to Aß-positive lvPPA. These measures did not differ between Aß-negative lvPPA and agPPA. Both lvPPA cohorts showed a higher mean length of utterance, more complex sentences, and fewer nouns than agPPA. Aß-negative lvPPA subjects appear unique and share linguistic features with both agPPA and Aß-positive lvPPA. Quantitative language analysis in lvPPA may be able to distinguish those with and without Aß deposition.