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. 2014 Sep 23;83(13):1184-91.
doi: 10.1212/WNL.0000000000000824. Epub 2014 Aug 27.

Asymmetry of Cortical Decline in Subtypes of Primary Progressive Aphasia

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Free PMC article

Asymmetry of Cortical Decline in Subtypes of Primary Progressive Aphasia

Emily Rogalski et al. Neurology. .
Free PMC article

Abstract

Objective: The aim of this study was to provide quantitative measures of changes in cortical atrophy over a 2-year period associated with 3 subtypes of primary progressive aphasia (PPA) using whole-brain vertex-wise and region-of-interest (ROI) neuroimaging methods. The purpose was to quantitate disease progression, establish an empirical basis for clinical expectations, and provide outcome measures for therapeutic trials.

Methods: Changes in cortical thickness and volume loss as well as neuropsychological performance were assessed at baseline and 2-year follow-up in 26 patients who fulfilled criteria for logopenic (8 patients), agrammatic (10 patients), and semantic (8 patients) PPA subtypes. Whole-brain vertex-wise and ROI imaging analysis were conducted using the FreeSurfer longitudinal pipeline.

Results: Clinical deficits and cortical atrophy patterns showed distinct patterns of change among the subtypes over 2 years. Results confirmed that progression for each of the 3 subtypes showed left greater than right hemisphere asymmetry. An ROI analysis also revealed that progression was greater within, rather than outside, the language network.

Conclusions: Preferential neurodegeneration of the left hemisphere language network is a common denominator for all 3 PPA subtypes, even as the disease progresses. Using a focal cortical language network ROI as an outcome measure of disease progression appears to be more sensitive than whole-brain or ventricular volume measures of change and may be helpful for designing future clinical trials in PPA.

Figures

Figure 1
Figure 1. Atrophy patterns by PPA subtype
False discovery rate was set at 0.05 for each comparison. (A) Significant cortical thinning patterns for each PPA subtype at baseline compared with controls (red/yellow shading). (B) Significant within-subject cortical thinning patterns over 2 years for each PPA subtype (blue/green shading). The p values are provided above each color bar. LH = left hemisphere; PPA = primary progressive aphasia; PPA-G = PPA-agrammatic; PPA-L = PPA-logopenic; PPA-S = PPA-semantic; RH = right hemisphere.
Figure 2
Figure 2. Individual left hemisphere ROI volumes by visit
PPA-G = primary progressive aphasia–agrammatic; PPA-L = primary progressive aphasia–logopenic; PPA-S = primary progressive aphasia–semantic; PSTC = perisylvian temporal cortex; ROI = region of interest.
Figure 3
Figure 3. Percent change of cortical volume loss over 2 years by hemisphere and PPA subtype
a Within each subtype and for each ROI the rate of change was significantly greater in the left hemisphere than in the right hemisphere. b Percent change was significantly higher in the PSTC than the remainder ROI for the left hemisphere for each subtype. c The left hemisphere PSTC ROI of the PPA-G group showed a significantly smaller percent change in volume than PPA-L and PPA-S groups. d The right hemisphere PSTC ROI of the PPA-G group showed a significantly smaller percent change in volume than the PPA-S group. Bars represent SDs. L = left hemisphere; PPA = primary progressive aphasia; PPA-G = PPA-agrammatic; PPA-L = PPA-logopenic; PPA-S = PPA-semantic; PSTC = perisylvian temporal cortex; R = right hemisphere; ROI = region of interest.

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