Primary progressive aphasia

A clinical syndrome with progressive language impairment as the principal initial problem. Detailed profiles distinguish loss of word meaning, motor speech difficulty, agrammatism and phonological-memory demands; a syndrome label is not a unique anatomical lesion or molecular pathology.

A PPA pattern involving word-finding pauses and impaired repetition, with phonological-memory limitations often important. Sentence length and syntactic complexity should be varied independently when testing comprehension.

A PPA pattern prominently affecting word and conceptual meaning. Failure to understand a sentence can arise from missing word knowledge even if some grammatical operations remain available.

A PPA pattern characterised by effortful or agrammatic language, often with apraxia of speech. Motor speech and syntactic comprehension should be measured separately; neither is established merely by slow output.