Primary progressive aphasia: the potential for change

Background: Primary progressive aphasia (PPA) is a dementia syndrome, characterised by the gradual, insidious loss of language. The most widely adopted definition of PPA conceptualises the syndrome as a focal dementia, targeting the language networks of the brain. Focal definitions are driven by assumptions of modularity, which have greatly influenced the research and clinical approaches employed by the field to date. This thesis examines the need for contemporary conceptualisations of PPA that consider the nature and psychosocial impact of the syndrome holistically, moving beyond the level of focal impairment and offering new theoretical perspectives and methodological approaches to the field. A dynamic systems account of PPA is presented as a novel theoretical alternative, conceptualising disease expression as the emergent output of a complex, self-organising system. Aims: The primary objectives of this thesis were to present, apply and test a dynamic systems framework of PPA through exploratory, proof of concept research. This aimed to provide a multi-layered account of PPA in order to uncover the dynamics of disease expression and its global consequences for behaviour and psychosocial wellbeing. These aims were addressed by: (1) quantifying and examining the system-wide expression of PPA across cognitive, linguistic, and social-emotional functions, and (2) exploring subjective-insights into the perceived nature of disease expression and associated psychosocial reactions to understand how individuals perceive, respond and adapt to language dissolution. Predictions: Given the exploratory nature of this research specific hypotheses were not formulated. Drawing upon a dynamic systems account of PPA broad predictions were made. It was predicted that the system-profiles and subjective-insights would provide evidence for the dynamic, multi-layered nature of PPA, while differentiating the participants with PPA from healthy ageing controls. Unique patterns of emotional and psychosocial adjustment were expected, highlighting the individualised nature of adaptation and disease expression. Methods and Procedures: Five individuals with a diagnosis of PPA and 14 healthy-ageing controls were recruited to the study. The data set for the entire thesis is based on this single PRIMARY PROGRESSIVE APHASIA: THE POTENTIAL FOR CHANGE 5 cohort of participants (PPA and controls) with an empirical focus on the individual cases with PPA. The small sample size was justified given the exploratory nature of the research and casecontrols design that aimed to examine the five individual systems in detail. All participants attended four evaluation sessions, completing a battery of objective and subjective measures of cognitive, linguistic, and social-emotional functions, including personal insights into disease expression and associated responses. This enabled comprehensive sampling of system performance and adaptation. The data collected were analysed across two levels providing different, yet complementary windows into the individual dynamic systems. Outcomes & Results: The multivariate, systems-approach to sampling, profiling and analysis provided rich and novel insights into the nature and psychosocial impact of PPA. The system-profiles revealed the multi-layered impact of PPA with performance decrements manifesting across cognitive, linguistic and social-emotional components of the system. This was further supported by the subjective-insights, with individuals with PPA perceiving significant linguistic impairment, as well as broader psychosocial and functional consequences of language dissolution. The system-profiles and subjective-insights differentiated the participants with PPA from the control group, providing preliminary support for the clinical utility of a systems-approach to PPA. Measures of linguistic performance and self-efficacy for social communication were particularly sensitive to language dissolution. Evidence for significant social-emotional impact of PPA, ranging from mild to profound, was a key finding of this research. Examples of maladaptive coping strategies were detected at an early disease stage, highlighting the need for timely diagnosis and proactive intervention. While some commonalities were evident across the system-profiles, the subjective-insights revealed unique patterns of adaptation and coping. Internal and external factors were identified with potential to influence individual patterns of disease expression and impact. PRIMARY PROGRESSIVE APHASIA: THE POTENTIAL FOR CHANGE 6 Conclusion: The primary aims of the thesis were achieved, providing preliminary support for a dynamic systems account of PPA. The findings suggest that the expression of PPA is dynamic and multi-layered, with individuals experiencing and adapting to language dissolution in unique ways. An intimate understanding of an individual’s system and personal construction of disease is advocated for identifying therapeutic goals and developing management plans with potential to bolster adaptation. Future research should test the preliminary findings on a larger sample of individuals with PPA, refining the theoretical framework and methodological approaches employed. PRIMARY PROGRESSIVE APHASIA: THE POTENTIAL FOR CHANGE 7 LIST OF ABBREVIATIONS AEMSS Ageand Educationcorrected MOANS Scaled Score AMSS Age-corrected MOANS Scaled Score BNT Boston Naming Test CIU Correct Information Unit CT Computed Tomography DRS Dementia Rating Scale DTI Diffusion Tensor Imaging GDS Geriatric Depression Scale ICF International Classification of Functioning, Disability and Health MRI Magnetic Resonance Imaging MOANS Mayo’s Older Americans Normative Studies PET Positron Emission Tomography PPA Primary Progressive Aphasia PPA-G Primary Progressive Aphasia – Grammatical PPA-L Primary Progressive Aphasia – Logopenic PPA-M Primary Progressive Aphasia – Mixed PPA-S Primary Progressive Aphasia – Semantic PROMPT Prompts for Restructuring Oral Muscular Phonetic Targets