Abstract
Language impairments caused by stroke (post-stroke aphasia, PSA) and neurodegeneration (primary progressive aphasia, PPA) have overlapping symptomatology, nomenclature and are classically divided into categorical subtypes. Surprisingly, PPA and PSA have rarely been directly compared in detail. Rather, previous studies have compared certain subtypes (e.g. semantic variants) or have focused on a specific cognitive/linguistic task (e.g. reading). This study assessed a large range of linguistic and cognitive tasks across the full spectra of PSA and PPA. We applied varimax-rotated principal component analysis to explore the underlying structure of the variance in the assessment scores. Similar phonological, semantic and fluency-related components were found for PSA and PPA. A combined principal component analysis across the two aetiologies revealed graded intra- and intergroup variations on all four extracted components. Classification analysis was used to test, formally, whether there were any categorical boundaries for any subtypes of PPA or PSA. Semantic dementia formed a true diagnostic category (i.e. within group homogeneity and distinct between-group differences), whereas there was considerable overlap and graded variations within and between other subtypes of PPA and PSA. These results suggest that (i) a multidimensional rather than categorical classification system may be a better conceptualization of aphasia from both causes; and (ii) despite the very different types of pathology, these broad classes of aphasia have considerable features in common.
Highlights
Aphasia is an impairment of the ability to comprehend and formulate language following acquired brain damage, which manifests as difficulties across multiple modalities of language use (Rosenbek et al, 1989)
Given that the two group-specific principal component analysis (PCA) results were similar in form, available post-stroke aphasia (PSA) patients were reassessed using a shared test battery derived from the progressive aphasia (PPA) test battery, so that all patients could be entered simultaneously into a unified PCA
Post-stroke aphasia The PCA for the PSA cohort was robust (Kaiser-MeyerOlkin = 0.84) and produced a four-factor rotated solution that accounted for 76.7% of variance in PSA patients’ performance (F1 = 30.4%, F2 = 17.5%, F3 = 15.2%, F4 = 13.7%)
Summary
Aphasia is an impairment of the ability to comprehend and formulate language following acquired brain damage, which manifests as difficulties across multiple modalities of language use (e.g. reading, auditory comprehension, expressive language) (Rosenbek et al, 1989). Causes of acquired brain damage leading to aphasia include stroke and neurodegeneration The latter cause results in a form of aphasia termed primary progressive aphasia (PPA) (Mesulam, 2001). Diagnostic subtypes have been proposed for both forms of aphasia, patients often vary greatly within each category or commonly fall between classifications (and are referred to as ‘mixed’). This suggests that the phenotype differences observed across patients might reflect graded variations across multidimensional aphasic spectra rather than a series of mutually exclusive, coherent diagnostic categories (Lambon Ralph et al, 2003; Stopford et al, 2008; Migliaccio et al, 2009; Ridgway et al, 2012; Warren et al, 2012). By combining detailed assessment data across the full ranges of PSA and PPA, this study was able to map out these graded inter- and intragroup variations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
