Twenty specialists in neurology and aphasiology, collaborating from leading hospitals and universities in Spain, the USA, and Chile, have published the results of a large-scale study using clinical data derived from persons with degenerative non-fluent speech-language involvement, in order to determine the degree and nature of overlap between their agrammatism – i.e., their variety of aphasic involvement – and their apraxia of speech – i.e., their motor-speech involvement. The goal of this project was to probe for the existence of naturally occurring, non-overlapping, meaningful indicators that could establish primary progressive aphasia (PPA) and primary progressive apraxia of speech (PPAoS) as distinct and independent clinical syndromes.
The researchers qualified 98 patients for this study, among them 43 whose neuropathological disease diagnosis was – postmortem – confirmed via autopsy. The patients were assessed quantitatively for expressive agrammatism via a picture-description task, using the picnic picture from the Western Aphasia Battery, and for receptive agrammatism via sentence comprehension tasks derived from the Curtis Yamada Comprehensive Language Evaluation. All patients underwent a comprehensive motor-speech evaluation for dysarthria and apraxia of speech in accord with criteria delineated by Wertz, LaPointe, and Rosenbek in their 1984 book, Apraxia of Speech in Adults. Organic cerebral disease severity was evaluated – at baseline and longitudinally – using the Clinical Dementia Rating Sum of Boxes.
Initial analysis of the clinical data showed that — of the 98 participants – 93 conformed with previously reported clinical profiles: 75 presented with both primary progressive agrammatism accompanied by apraxia of speech, 12 presented with primary progressive apraxia of speech absent agrammatism, and 6 presented with primary progressive agrammatism absent accompanying apraxia of speech. The remaining five participants presented with neither diagnosable agrammatism nor diagnosable apraxia of speech, but rather with executive dysfunction and co-occurring dysarthria. Analytic software was used to process the data from the 93 participants of familiar profiles, to identify clustering tendencies and probe the robustness of symptom cluster formations. Results of these latter analyses suggest that PPA and PPAoS — rather than existing as distinct syndromic entities — represent varieties of presentation within one clinical continuum. In this context, the authors indicate a need for further research, both to identify new biological markers, and to establish consensus around updated clinical classification and associated terminology.
For further reading: I. Illán-Gala, D. L. Lorca-Puls, B. L. Tee et al., 2024, Clinical dimensions along the non-fluent variant primary progressive aphasia spectrum. Brain, 147(4): 1511–1525. https://doi.org/10.1093/brain/awad396