Primary progressive aphasia: a clinical approach

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Abstract

The primary progressive aphasias are a heterogeneous group of focal ‘language-led’ dementias that pose substantial challenges for diagnosis and management. Here we present a clinical approach to the progressive aphasias, based on our experience of these disorders and directed at non-specialists. We first outline a framework for assessing language, tailored to the common presentations of progressive aphasia. We then consider the defining features of the canonical progressive nonfluent, semantic and logopenic aphasic syndromes, including ‘clinical pearls’ that we have found diagnostically useful and neuroanatomical and other key associations of each syndrome. We review potential diagnostic pitfalls and problematic presentations not well captured by conventional classifications and propose a diagnostic ‘roadmap’. After outlining principles of management, we conclude with a prospect for future progress in these diseases, emphasising generic information processing deficits and novel pathophysiological biomarkers.

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The online version of this article (10.1007/s00415-018-8762-6) contains supplementary material, which is available to authorized users.

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Structure and deterioration of semantic memory: a neuropsychological and computational investigation.

Timothy Rogers, Matthew A. Lambon Ralph, Peter Garrard … (2004)

Wernicke (1900, as cited in G. H. Eggert, 1977) suggested that semantic knowledge arises from the interaction of perceptual representations of objects and words. The authors present a parallel distributed processing implementation of this theory, in which semantic representations emerge from mechanisms that acquire the mappings between visual representations of objects and their verbal descriptions. To test the theory, they trained the model to associate names, verbal descriptions, and visual representations of objects. When its inputs and outputs are constructed to capture aspects of structure apparent in attribute-norming experiments, the model provides an intuitive account of semantic task performance. The authors then used the model to understand the structure of impaired performance in patients with selective and progressive impairments of conceptual knowledge. Data from 4 well-known semantic tasks revealed consistent patterns that find a ready explanation in the model. The relationship between the model and related theories of semantic representation is discussed.

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Primary progressive aphasia and the evolving neurology of the language network.

M-Marsel Mesulam, Emily Rogalski, Christina Wieneke … (2014)

Primary progressive aphasia (PPA) is caused by selective neurodegeneration of the language-dominant cerebral hemisphere; a language deficit initially arises as the only consequential impairment and remains predominant throughout most of the course of the disease. Agrammatic, logopenic and semantic subtypes, each reflecting a characteristic pattern of language impairment and corresponding anatomical distribution of cortical atrophy, represent the most frequent presentations of PPA. Such associations between clinical features and the sites of atrophy have provided new insights into the neurology of fluency, grammar, word retrieval, and word comprehension, and have necessitated modification of concepts related to the functions of the anterior temporal lobe and Wernicke's area. The underlying neuropathology of PPA is, most commonly, frontotemporal lobar degeneration in the agrammatic and semantic forms, and Alzheimer disease (AD) pathology in the logopenic form; the AD pathology often displays atypical and asymmetrical anatomical features consistent with the aphasic phenotype. The PPA syndrome reflects complex interactions between disease-specific neuropathological features and patient-specific vulnerability. A better understanding of these interactions might help us to elucidate the biology of the language network and the principles of selective vulnerability in neurodegenerative diseases. We review these aspects of PPA, focusing on advances in our understanding of the clinical features and neuropathology of PPA and what they have taught us about the neural substrates of the language network.

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Considering the role of semantic memory in episodic future thinking: evidence from semantic dementia.

John R. Hodges, Muireann Irish, Olivier Piguet … (2012)

Semantic dementia is a progressive neurodegenerative condition characterized by the profound and amodal loss of semantic memory in the context of relatively preserved episodic memory. In contrast, patients with Alzheimer's disease typically display impairments in episodic memory, but with semantic deficits of a much lesser magnitude than in semantic dementia. Our understanding of episodic memory retrieval in these cohorts has greatly increased over the last decade, however, we know relatively little regarding the ability of these patients to imagine and describe possible future events, and whether episodic future thinking is mediated by divergent neural substrates contingent on dementia subtype. Here, we explored episodic future thinking in patients with semantic dementia (n=11) and Alzheimer's disease (n=11), in comparison with healthy control participants (n=10). Participants completed a battery of tests designed to probe episodic and semantic thinking across past and future conditions, as well as standardized tests of episodic and semantic memory. Further, all participants underwent magnetic resonance imaging. Despite their relatively intact episodic retrieval for recent past events, the semantic dementia cohort showed significant impairments for episodic future thinking. In contrast, the group with Alzheimer's disease showed parallel deficits across past and future episodic conditions. Voxel-based morphometry analyses confirmed that atrophy in the left inferior temporal gyrus and bilateral temporal poles, regions strongly implicated in semantic memory, correlated significantly with deficits in episodic future thinking in semantic dementia. Conversely, episodic future thinking performance in Alzheimer's disease correlated with atrophy in regions associated with episodic memory, namely the posterior cingulate, parahippocampal gyrus and frontal pole. These distinct neuroanatomical substrates contingent on dementia group were further qualified by correlational analyses that confirmed the relation between semantic memory deficits and episodic future thinking in semantic dementia, in contrast with the role of episodic memory deficits and episodic future thinking in Alzheimer's disease. Our findings demonstrate that semantic knowledge is critical for the construction of novel future events, providing the necessary scaffolding into which episodic details can be integrated. Further research is necessary to elucidate the precise contribution of semantic memory to future thinking, and to explore how deficits in self-projection manifest on behavioural and social levels in different dementia subtypes.

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Author and article information

Contributors

Charles R. Marshall: 44 203 448 3653 , charles.marshall@ucl.ac.uk

Jason D. Warren: 44 0203 448 4773 , jason.warren@ucl.ac.uk

Journal

Journal ID (nlm-ta): J Neurol

Journal ID (iso-abbrev): J. Neurol

Title: Journal of Neurology

Publisher: Springer Berlin Heidelberg (Berlin/Heidelberg )

ISSN (Print): 0340-5354

ISSN (Electronic): 1432-1459

Publication date (Electronic): 1 February 2018

Publication date PMC-release: 1 February 2018

Publication date (Print): 2018

Volume: 265

Issue: 6

Pages: 1474-1490

Affiliations

[1 ]ISNI 0000000121901201, GRID grid.83440.3b, Department of Neurodegenerative Disease, , Dementia Research Centre, UCL Institute of Neurology, ; Queen Square, London, WC1N 3BG UK

[2 ]ISNI 0000000121901201, GRID grid.83440.3b, Division of Psychology and Language Sciences, , University College London, ; London, UK

Article

Publisher ID: 8762

DOI: 10.1007/s00415-018-8762-6

PMC ID: 5990560

PubMed ID: 29392464

SO-VID: fbbba125-1c57-4e17-b043-bd57beb1ba68

License:

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

History

Date received : 29 November 2017

Date revision received : 18 January 2018

Date accepted : 19 January 2018

Funding

Funded by: FundRef http://dx.doi.org/10.13039/100004440, Wellcome Trust;

Award ID: 091673/Z/10/Z

Award Recipient : Jason D. Warren

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ScienceOpen disciplines: Neurology

Keywords: primary progressive aphasia,semantic dementia,logopenic aphasia,frontotemporal dementia,alzheimer’s disease

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ScienceOpen disciplines: Neurology

Keywords: primary progressive aphasia, semantic dementia, logopenic aphasia, frontotemporal dementia, alzheimer’s disease

Primary progressive aphasia: a clinical approach

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Most cited references 97

Structure and deterioration of semantic memory: a neuropsychological and computational investigation.

Primary progressive aphasia and the evolving neurology of the language network.

Considering the role of semantic memory in episodic future thinking: evidence from semantic dementia.

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