FDG PET and MRI in Logopenic Primary Progressive Aphasia versus Dementia of the Alzheimer’s Type

Abstract

ObjectivesThe logopenic variant of 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. We aimed to characterize and compare patterns of atrophy and hypometabolism in logopenic primary progressive aphasia, and determine which brain regions and imaging modality best differentiates logopenic primary progressive aphasia from typical dementia of the Alzheimer’s type.MethodsA total of 27 logopenic primary progressive aphasia subjects underwent fluorodeoxyglucose positron emission tomography and volumetric magnetic resonance imaging. These subjects were matched to 27 controls and 27 subjects with dementia of the Alzheimer’s type. Patterns of atrophy and hypometabolism were assessed at the voxel and region-level using Statistical Parametric Mapping. Penalized logistic regression analysis was used to determine what combinations of regions best discriminate between groups.ResultsAtrophy and hypometabolism was observed in lateral temporoparietal and medial parietal lobes, left greater than right, and left frontal lobe in the logopenic group. The logopenic group showed greater left inferior, middle and superior lateral temporal atrophy (inferior p = 0.02; middle p = 0.007, superior p = 0.002) and hypometabolism (inferior p = 0.006, middle p = 0.002, superior p = 0.001), and less right medial temporal atrophy (p = 0.02) and hypometabolism (p<0.001), and right posterior cingulate hypometabolism (p<0.001) than dementia of the Alzheimer’s type. An age-adjusted penalized logistic model incorporating atrophy and hypometabolism achieved excellent discrimination (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.ConclusionsPatterns of atrophy and hypometabolism both differ between logopenic primary progressive aphasia and dementia of the Alzheimer’s type and both modalities provide excellent discrimination between groups.

Tau PET patterns mirror clinical and neuroanatomical variability in Alzheimer’s disease

“…Based on previous neuroimaging studies (Rabinovici et al, 2008;Madhavan et al, 2013;Teichmann et al, 2013;Rogalski et al, 2014;Ossenkoppele et al, 2015a) and the specific language presentation, we hypothesized that patients with logopenic variant PPA would show 18 F-AV1451 uptake in temporoparietal language regions in a clearly asymmetric fashion with greater tau in the left hemisphere compared to right hemisphere. Visual inspection of individual images and a quantitative laterality index indicated that three logopenic variant PPA showed the predicted left 4 right pattern, one was fairly symmetric and one patient had greater 18 F-AV1451 uptake in right than in left hemisphere.…”

“…Among many other applications, amyloid-b imaging has been incorporated into diagnostic criteria for various stages of the disease (Albert et al, 2011;McKhann et al, 2011;Sperling et al, 2011;Dubois et al, 2014), has substantial impact on clinical decision-making (Ossenkoppele et al, 2013a;Sanchez-Juan et al, 2014) and patient management plans (Schipke et al, 2012;Grundman et al, 2013), and has shown potential as a surrogate outcome measure in clinical trials tailored to reduce cerebral amyloid-b plaque burden (Salloway et al, 2014;Liu et al, 2015). A yet unresolved issue after a decade of amyloid-b imaging research, however, is the disconnection between the diffuse distribution of amyloid-b pathology throughout the neocortex (Rabinovici et al, 2010;Wolk et al, 2012;Lehmann et al, 2013;Jung et al, 2015) and the selective patterns of brain atrophy and glucose hypometabolism that strongly correlate with clinical symptoms (Rabinovici et al, 2010;Ridgway et al, 2012;Lehmann et al, 2013;Madhavan et al, 2013). Thus, although amyloid-b deposition may be a prerequisite to developing Alzheimer's disease dementia, at some point during the disease course additional factors are likely involved in determining regional neurodegeneration and symptomatology.…”

Regional Distribution, Asymmetry, and Clinical Correlates of Tau Uptake on [18F]AV-1451 PET in Atypical Alzheimer’s Disease

“…The main regions of involvement in PCA include the occipital, parietal, and occipito-temporal regions [17, 19], while those affected in lvPPA include the posterior portions of the superior and middle temporal lobe, the inferior parietal lobe, and the temporo-parietal junction [20, 21]. Patterns of neurodegeneration are usually asymmetric in lvPPA, involving the left hemisphere greater than right, and can also be asymmetric in PCA [22], more commonly involving the right hemisphere.…”

Particularités du variant logopénique au sein des aphasies progressives primaires

“…Ce pattern est comparable à celui retrouvé dans les cas de maladie d'Alzheimer typique (amné sique au stade dé mentiel) à pré dominance gauche [68,71]. L'atteinte temporale externe et frontale infé rieure gauche est cependant plus importante dans l'aphasie progressive primaire logopé nique ce qui permettrait une bonne façon de distinguer ces deux entité s [72]. Il en est de mê me pour les atrophies corticales posté rieures [73] malgré des zones de chevauchement de l'atrophie dans le carrefour parié totemporal gauche [61,74].…”

“…Ceci permet de le diffé rencier des autres types d'APP ayant des atteintes plus anté rieures, à l'exception du type fluent anomique, correspondant probablement à une forme prodromique des diffé rentes formes d'APP [86]. Ce pattern permet aussi de bien diffé rencier l'APP logopé -nique de la maladie d'Alzheimer typique (amné sique au stade dé mentiel) [72,87]. Par ailleurs, l'imagerie nuclé aire type PET ou SPECT est plus fré quemment contributive pour mettre en é vidence une anomalie du carrefour parié totemporal gauche né cessaire au diagnostic que l'imagerie anatomique type IRM (86 à 90 % vs 57 à 60 %) [34,88].…”