To characterize the neuroimaging, neuropsychologic features, and longitudinal outcomes of an anomic subtype of Primary Progressive Aphasia (PPA).

Many patients who have progressive aphasia do not meet criteria for the established PPA subtypes (Logopenic (LPA), Semantic (SD), or Agrammatic). One such subset presents with prominent anomia with spared repetition, grammar, motor speech, and semantic knowledge. We propose the term Anomic Progressive Aphasia (APA) to describe these cases and hypothesize that they represent mild cases of fluent aphasia that will ultimately progress to meet criteria for LPA, SD, or mixed SD-LPA.

Retrospective analysis identified 30 patients with possible APA recruited by the Neurodegenerative Research Group at Mayo Clinic between 2011-2021. Chart review and neuropsychological/language testing were used to exclude those with impaired repetition, semantic knowledge, grammar, or motor speech. We excluded those with moderate aphasia (WAB-AQ< 85) or significant cognitive impairment.

Nine patients were included (6 females, 3 males), with average education 16.5 years, average age at onset 66, and mean WAB-AQ 89.9 at presentation. Three of eight (38%) were amyloid-positive on PiB-PET, one of whom was also tau-positive on AV-1451-PET; two developed LPA and one had mixed SD-LPA. Two patients were tau-positive only, although on visual inspection likely due to off-target binding commonly associated with TDP-43 Type C pathology; both progressed to SD. Two with left anteromedial temporal hypometabolism on FDG-PET progressed to SD. Three with posterolateral temporal hypometabolism (two left, one right) progressed to LPA, two of whom also had parietal and frontal hypometabolism. One with left anteromedial temporal and frontal hypometabolism developed mixed SD-LPA. Three with parietal or frontal hypometabolism developed features of LPA (one mixed).

APA lies on the spectrum of aphasic disorders that do not clearly fit into established PPA subtypes. Molecular PET and FDG PET may help to predict the clinical course of APA.