Acoustic Analysis of Apraxia of Speech in a Japanese Patient With Nonfluent/Agrammatic Variant Primary Progressive Aphasia: A Case Study

Apraxia of speech (AOS) is a motor speech disorder often observed in the nonfluent/agrammatic variant of primary progressive aphasia (nfvPPA). While acoustic analysis has proven useful in identifying AOS features in English speakers, data on Japanese speakers are limited. This study investigated the acoustic characteristics of AOS in a 70-year-old Japanese woman diagnosed with corticobasal syndrome and nfvPPA. Speech and neuropsychological assessments revealed typical AOS features. Acoustic measures included triangular vowel space area (tVSA), voice onset time (VOT), and speech duration. As a result, although tVSA was relatively preserved, both VOT and speech duration were prolonged. These findings suggest that VOT and speech duration may serve as effective acoustic markers for detecting AOS in Japanese, providing useful objective indicators for diagnosis and treatment planning.