Speech profiles in stroke aphasia and AOS (Haley & Jacks, 2023)
Purpose: Behaviorally, acquired apraxia of speech (AOS) is a multidimensional syndrome that the experienced clinician recognizes based on impaired articulation and abnormal temporal prosody. We conducted this study to determine the extent to which three core features of AOS—when defined quantitatively—distinguish categorically among aphasia with no or minimal speech sound involvement, aphasia with AOS, and aphasia with phonemic paraphasia (APP).
Method: The study involved retrospective analysis of 195 participants with stroke-induced aphasia. We used three quantitative measures (phonemic error frequency, distortion error frequency, and word syllable duration [WSD]) to divide the sample into four participant groups according to the most likely speech diagnosis: aphasia with minimal speech sound errors, AOS, APP, and a borderline group with mixed profiles. We then conducted nonparametric comparisons across groups for which the measures were not defined and visualized all three measures in a three-dimensional graph.
Results: The measures distributed as multidimensional spectra rather than discrete diagnostic entities, and there was considerable behavioral overlap among participant groups. Thirty percent of participants presented with aphasia with minimal sound production difficulties, and they were statistically indistinguishable from the APP group on distortion frequency and WSD. Distortion frequency and WSD were in a borderline region between AOS and APP for 29% of participants. Compared to all other groups, participants with AOS produced significantly more errors that affected listeners’ phonemic perception.
Conclusions: The results suggest that the current AOS–APP dichotomy has limited validity. We conclude that a continuous multidimensional view of speech variation would be a constructive perspective from which to understand how the left cerebral hemisphere produces speech and that quantitative and normed speech measures should be used to inform differential diagnosis in clinical settings.
Supplemental Material S1. A rotating version of a three-dimensional scatter plot showing the relationship among phonemic error frequency, distortion error frequency, and word syllable duration (WSD). The ellipsoids represent a normal contour based on the distribution of each variable and cover 50% of the data points in each group. All measures were transformed using a natural logarithm to better visualize nonnormal distributions of data. MIN = minimal sound production difficulties; APP = probable aphasia with phonemic paraphasia; BL = borderline profile; AOS = probable apraxia of speech.
Haley, K. L., & Jacks, A. (2023). Three-dimensional speech profiles in stroke aphasia and apraxia of speech. American Journal of Speech-Language Pathology. Advance online publication. https://doi.org/10.1044/2022_AJSLP-22-00170
Publisher Note: This article is part of the Special Issue: Select Papers From the 2022 Conference on Motor Speech.