Chinese Language Assessment in Primary Progressive Aphasia (CLAP) workgroup
Correspondence: Dr. Boon Lead Tee, boonlead.tee@ucsf.edu
Study Question: What are the dysgraphia presentations of primary progressive aphasia (PPA) patients who write in Chinese script?
What is Known and What This Papers Adds: Studies on English language speakers with PPA show that individuals with semantic variant PPA commonly present with surface dysgraphia, and logopenic variant PPA and nonfluent/agrammatic variant PPA patients are more frequently found to exhibit phonological dysgraphia. There is lack of evidence on the occurrence of such dysgraphia phenotypes in PPA patients that write in logographic writing systems. The present study characterized the dysgraphia phenotypes of PPA patients who use Chinese logographic script and investigated their diagnostic utility in classifying PPA variants.
Methods: This international multicenter cross-sectional study measured orthographic dictation accuracy using the CLAP 60-character orthographic dictation test in 40 PPA participants and 20 cognitively-normal participants from San Francisco, Hong Kong, and Taiwan. Aside from dictation accuracy, the writing errors were categorized based on the previous literature and a group consensus. We also examined the occurrence of various writing errors across the study groups using principal component analysis. To identify the cortical regions significantly correlated with dictation accuracy and the occurrence of various writing errors, we performed voxel-based morphometry analysis with multiple linear regression models adjusted for age, education, total grey matter volume, diagnosis, and/or dictation accuracy.
Results and Study Limitations: Patients in all PPA groups produced significantly less accurate writing responses than the control group, and no significant differences in dictation accuracy were noted among the PPA variants. Dictation accuracy was correlated with volumetric changes over left ventral temporal cortices, regions known to be critical for orthographic long-term memory. Individuals with semantic variant PPA frequently presented with phonologically plausible errors at lexical level; logopenic variant PPA patients showed higher preponderance towards visual and stroke errors; and nonfluent/agrammatic variant PPA patients commonly exhibited compound word and radical errors. The prevalence of phonologically plausible, visual and compound word errors was negatively correlated with cortical volume over the bilateral temporal regions, left temporo-occipital area, and bilateral orbitofrontal gyri, respectively. Limitations of this study include possible interpretation bias due to lack of harmonizable executive and visuospatial data and reduced availability for standardized MRI images, demographic heterogeneity caused by diverse recruitment sources, and uncertain generalizability in simplified Chinese script writers.
