Syntactic impairments can emerge later: Progressive agrammatic agraphia and syntactic comprehension impairment

Background & Aims: Recent studies suggest that agrammatism is not a major feature of progressive nonfluent aphasia, at least not in the earlier years post-onset. We investigated the emergence of syntactic impairments over a 3-year period in CS, a 63-year-old man 8 years post-onset of progressive speech difficulties. CS has a range of progressive cognitive impairments, including progressive nonfluent aphasia, and limb and other apraxias (with a progressive non-aphasic and mostly non-dysarthric speech deterioration), but relatively intact intelligence, perception, orientation, long-term memory, semantics, and phonology. Writing impairments did not emerge until some 8 years after naming and speech impairments were first noticed, and after CS became mute. Methods & Procedures: We undertook detailed longitudinal examination of word and sentence writing and syntactic comprehension across a range of tasks and examined the impact of short-term memory. We were concerned to examine the data for evidence of agrammatic features, particularly in noun and verb use, and use of formulaic and simplified syntactic structures as the condition progressed. Outcomes & Results: Analysis showed a progressive emergence of deficits on tests of written syntax, syntactic comprehension, and auditory-verbal short-term memory. There was a progressive reduction in verb and noun use, but this was related to the kind of stimulus used. Features of agrammatism were evident in writing with a progressive dependence on formulaic and simplified syntax. Conclusions: It may be that agrammatism in PNFA is a feature that develops late in the progression, showing up only in writing because it is masked in speech by motor speech impairment. Increasing reliance on formulaic and simplified structures with progression suggests compensatory adaptation of CS's system. Impairments appeared to emerge in parallel with deterioration of syntactic comprehension and phonological short-term memory.