Heterogeneity in Progressive Aphasia Due to Focal Cortical Atrophy

Tyrrell, Pippa J.; Warrington, Elizabeth K.; Frackowiak, R. S. J.; Rossor, Martin N.

doi:10.1093/brain/113.5.1321

Cited by 138 publications

(14 citation statements)

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“…19 -21 Moreover, positron emission tomography (PET) and single-photon emission computerized tomography in patients with PPA have shown restingstate deficits in cortical metabolism and blood flow in left anterior and posterior perisylvian regions. 2,[22][23][24] Although some right-sided abnormalities have been found in a few cases, the metabolic state of the right hemisphere generally has been within normal limits in these studies. Thus, resting functional imaging data have largely reflected the clinical focality of PPA.…”

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confidence: 63%

Primary progressive aphasia: PPA and the language network

Sonty

Mesulam

Thompson

et al. 2002

Annals of Neurology

132

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Primary Progressive Aphasia (PPA) is a behaviorally focal dementia syndrome with deterioration of language functions but relative preservation of other cognitive domains for at least the first two years of disease. In this study, PPA patients with impaired word finding but intact comprehension of conversational speech and their matched control subjects were examined using voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI). fMRI compared signal changes during phonological and semantic language tasks with those during a control task (matching letters). PPA patients showed longer reaction times and reduced accuracy versus controls on the language tasks, but no performance differences on the control task. VBM demonstrated reduced gray matter in left superior temporal and inferior parietal regions in the PPA group. However, these patients showed a normal pattern of activation within the classical language regions. In addition, PPA patients showed activations, not seen in normals, in fusiform gyrus, precentral gyrus, and intra-parietal sulcus. These activations were found to correlate negatively with measures of naming and task performance. The additional activations in PPA may therefore represent a compensatory spread of language-related neural activity or a failure to suppress activity in areas normally inhibited during language tasks.

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confidence: 63%

Primary progressive aphasia: PPA and the language network

Sonty

Mesulam

Thompson

et al. 2002

Annals of Neurology

132

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“…Since the first landmark studies [40,41] 18 F-FDG-PET functional investigations have provided consistent findings of bilateral hypometabolism in temporal lobes, peaking in the TPs, and usually prevalent to the left [24,42–48]. Some authors have reported an additional involvement of the basal ganglia (caudate nucleus), thalamus [42,43,45], subcallosal gyrus/orbitofrontal cortex (SCG, OFC) [24,42,44,46], insula [42,49], anterior cingulate cortex (aCG) [50], and fusiform gyrus (FFG) [24,43,44,46,47].…”

Section: Introductionmentioning

confidence: 99%

The Semantic Variant of Primary Progressive Aphasia: Clinical and Neuroimaging Evidence in Single Subjects

et al. 2015

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Background/AimWe present a clinical-neuroimaging study in a series of patients with a clinical diagnosis of semantic variant of primary progressive aphasia (svPPA), with the aim to provide clinical-functional correlations of the cognitive and behavioral manifestations at the single-subject level.MethodsWe performed neuropsychological investigations, 18F-FDG-PET single-subject and group analysis, with an optimized SPM voxel-based approach, and correlation analyses. A measurement of white matter integrity by means of diffusion tensor imaging (DTI) was also available for a subgroup of patients.ResultsCognitive assessment confirmed the presence of typical semantic memory deficits in all patients, with a relative sparing of executive, attentional, visuo-constructional, and episodic memory domains. 18F-FDG-PET showed a consistent pattern of cerebral hypometabolism across all patients, which correlated with performance in semantic memory tasks. In addition, a majority of patients also presented with behavioral disturbances associated with metabolic dysfunction in limbic structures. In a subgroup of cases the DTI analysis showed FA abnormalities in the inferior longitudinal and uncinate fasciculi.DiscussionEach svPPA individual had functional derangement involving an extended, connected system within the left temporal lobe, a crucial part of the verbal semantic network, as well as an involvement of limbic structures. The latter was associated with behavioral manifestations and extended beyond the area of atrophy shown by CT scan.ConclusionSingle-subject 18F-FDG-PET analysis can account for both cognitive and behavioral alterations in svPPA. This provides useful support to the clinical diagnosis.

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“…In contrast to other degenerative dementias, attention, memory, and other cognitive functions are relatively preserved within initial phases of illness. PPA has been associated with circumscribed atrophy and functional disruption in left-hemisphere perisylvian and temporal brain regions (Chawluk et al, 1986;Tyrrell et al, 1990;Abe et al, 1997;Westbury and Bub, 1997;Sonty et al, 2003;Gorno-Tempini et al, 2004). The behavioral and structural focality of PPA make it an important model for studying the functional anatomy of language and the effects of degenerative disease on brain function.…”

Section: Introductionmentioning

confidence: 99%

Altered Effective Connectivity within the Language Network in Primary Progressive Aphasia

Sonty¹,

Mesulam²,

Weıntraub³

et al. 2007

J. Neurosci.

122

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Primary progressive aphasia (PPA) is a neurodegenerative dementia syndrome principally characterized by the gradual dissolution of language functions, especially in the early stages of disorder. In a previous functional neuroimaging study, PPA patients were found to activate core language areas similarly to control subjects when performing semantic and phonological processing tasks (Sonty et al., 2003). In the present study, functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) were used to study multiregional effective connectivity in early-stage PPA (n ϭ 8) and control (n ϭ 8) subjects performing semantic word matching and visual letter matching tasks. fMRI analysis showed semantic task-specific activations in the left inferior frontal (Broca's area) and posterior superior temporal (Wernicke's area) regions, in addition to other language regions, in both groups. Using a model language network consisting of six left hemisphere regions, the DCM analysis demonstrated reduced language-specific effective connectivity between Wernicke's and Broca's areas in the PPA patient group. Furthermore, this decrement in connectivity was predictive of semantic task accuracy. These results demonstrate for the first time that dysfunctional network interactions (effective connectivity), rather than hypoactivity within individual brain regions, may contribute to the emergence of language deficits seen in PPA.

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Heterogeneity in Progressive Aphasia Due to Focal Cortical Atrophy

Cited by 138 publications

References 0 publications

Primary progressive aphasia: PPA and the language network

Primary progressive aphasia: PPA and the language network

The Semantic Variant of Primary Progressive Aphasia: Clinical and Neuroimaging Evidence in Single Subjects

Altered Effective Connectivity within the Language Network in Primary Progressive Aphasia

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