Dysgraphia Phenotypes in Native Chinese Speakers With Primary Progressive Aphasia
Neurology. 2022 Apr 11:10.1212/WNL.0000000000200350. doi: 10.1212/WNL.0000000000200350. Online ahead of print.
BACKGROUND AND OBJECTIVES: To date, most primary progressive aphasia (PPA) literature is based on English language users. Naturally, linguistic features that vary from English, such as logographic writing systems, are under-investigated. The present study characterized the dysgraphia phenotypes of PPA patients who write in Chinese and investigated their diagnostic utility in classifying PPA variants.
METHODS: This study recruited 40 PPA participants and 20 cognitively-normal participants from San Francisco, Hong Kong, and Taiwan. We measured dictation accuracy using the Chinese Language Assessment for PPA (CLAP) 60-character orthographic dictation test and examined the occurrence of various writing errors across the study groups. We also performed voxel-based morphometry analysis to identify the grey matter regions correlated with dictation accuracy and prevalence of writing errors.
RESULTS: 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. With a cut-score of 36 out of 60 in the CLAP orthographic dictation task, the test achieved sensitivity and specificity of 90% and 95% in identifying Chinese PPA participants from controls. In addition to a character frequency effect, dictation accuracy was also affected by homophone density and the number of strokes in svPPA and lvPPA groups. 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.
DISCUSSION: The findings demonstrate the potential role of the orthographic dictation task as a screening tool and PPA classification indicator in Chinese language users. Each PPA variant had specific Chinese dysgraphia phenotypes that vary from those previously reported in English PPA patients, highlighting the importance of language diversity in PPA.