MRI in Logopenic Primary Progressive Aphasia vs Dementia AD

Primary progressive aphasia is an atypical clinical variant of Alzheimer’s disease which is typically characterized by left temporoparietal atrophy on magnetic resonance imaging and hypometabolism on F-18 fluorodeoxyglucose positron emission tomography.

Atrophy and hypometabolism was observed in lateral temporoparietal and medial parietal lobes, left greater than right, and left frontal lobe in the logopenic group. An age-adjusted penalized logistic model incorporating atrophy and hypometabolism achieved region (area under the receiver operator characteristic curve = 0.89) between logopenic and dementia of the Alzheimer’s type subjects, with optimal discrimination achieved using right medial temporal and posterior cingulate hypometabolism, left inferior, middle and superior temporal hypometabolism, and left superior temporal volume. Patterns of atrophy and hypometabolism both differ between logopenic primary progressive aphasia and dementia of the AD.

(PPA) is a language disorder that is characterized by deficits in functions such as object naming, syntax, and word-processing. Examine the relationship between patterns of hypometabolism and grey matter atrophy in lvPPA and determine which combination of regions best differentiate lvPPA from DAT.

The clinical criteria used for lvPPA were as follows: 1) presence of aphasia, 2) impaired sentence repetition and comprehension, 3) presence of anomia with evidence of spared single word comprehension, 4) evidence of phonemic paraphasias, 5) normal rate of verbal expression or slowed verbal expression due to pauses for word retrieval without evidence of motoric slowing, and 6) absence of agrammatic/telegraphic verbal output. All 27 subjects also met recently published clinical diagnostic criteria for lvPPA.

Images acquired both scans were performed as previously described on the same day with 1 hour between acquisitions

Voxel-level imaging findings in lvPPA and DAT when compared to controls.

Three dimensional renderings show regions of reduced FDG metabolism and gray matter (GM) volume in lvPPA compared to controls and in DAT compared to controls. All images were generated using an FDR corrected statistical threshold of p<0.0005 and an extent threshold of 100 voxels. A decrease in brightness of the render reflects increased distance from the surface of the tissue.   

Voxel-level imaging comparison of lvPPA and DAT.

Three dimensional renderings show regions of reduced FDG metabolism and gray matter (GM) volume in lvPPA compared to DAT, and in DAT compared to lvPPA. All images were generated using an uncorrected statistical threshold of p<0.001 and an extent threshold of 100 voxels. A decrease in brightness of the render reflects increased distance from the surface of the tissue.

Estimated coefficients from multivariable penalized logistic regression analyses.

Estimated AUROC and a 95% bootstrap confidence interval are shown in the top left of each panel.

Region-level imaging comparison of lvPPA and DAT.

Age-adjusted odds ratios and 95% CIs on the logarithm scale for a 1-SD change in the imaging variable. The vertical dashed line represents an odds ratio of 1.0. Estimates to the left of the vertical line indicate pathology tended to be greater in lvPPA. Estimates to the right of the vertical line indicate pathology tended to be less in lvPPA. 95% CIs that do not cross the dashed line represent significant differences between groups.