Grammatical comprehension deficits in non-fluent/agrammatic primary progressive aphasia.

IMPORTANCE

Grammatical comprehension difficulty is an essential supporting feature of the non-fluent/agrammatic variant of primary progressive aphasia (naPPA), but well-controlled clinical measures of grammatical comprehension are unavailable.

OBJECTIVE

To develop a measure of grammatical comprehension and examine this comparatively in PPA variants and behavioural-variant frontotemporal degeneration (bvFTD) and to assess the neuroanatomic basis for these deficits with volumetric grey matter atrophy and whole-brain fractional anisotropy (FA) in white matter tracts.

DESIGN

Case-control study.

SETTING

Academic medical centre.

PARTICIPANTS

39 patients with variants of PPA (naPPA=12, lvPPA=15 and svPPA=12), 27 bvFTD patients without aphasia and 12 healthy controls.

MAIN OUTCOME MEASURE: Grammatical comprehension accuracy.

RESULTS

Patients with naPPA had selective difficulty understanding cleft sentence structures, while all PPA variants and patients with bvFTD were impaired with sentences containing a centre-embedded subordinate clause. Patients with bvFTD were also impaired understanding sentences involving short-term memory. Linear regressions related grammatical comprehension difficulty in naPPA to left anterior-superior temporal atrophy and reduced FA in corpus callosum and inferior frontal-occipital fasciculus. Difficulty with centre-embedded sentences in other PPA variants was related to other brain regions.

CONCLUSIONS AND RELEVANCE: These findings emphasise a distinct grammatical comprehension deficit in naPPA and associate this with interruption of a frontal-temporal neural network.