Temporal acoustic measures distinguish primary progressive apraxia of speech from primary progressive aphasia

•Diagnosis of primary progressive apraxia of speech (PPAOS) can be challenging.•Acoustic measures’ ability to distinguish PPAOS from PPA was assessed.•Measures of duration, rate and lexical stress distinguished PPAOS from PPA.•Acoustic measures can serve as a confirmatory diagnostic marker for PPAOS. The purpose of this study was to determine if acoustic measures of duration and syllable rate during word and sentence repetition, and a measure of within-word lexical stress, distinguish speakers with primary progressive apraxia of speech (PPAOS) from nonapraxic speakers with the agrammatic or logopenic variants of primary progressive aphasia (PPA), and control speakers. Results revealed that the PPAOS group had longer durations and reduced rate of syllable production for most words and sentences, and the measure of lexical stress. Sensitivity and specificity indices for the PPAOS versus the other groups were highest for longer multisyllabic words and sentences. For the PPAOS group, correlations between acoustic measures and perceptual ratings of AOS were moderately high to high. Several temporal measures used in this study may aid differential diagnosis and help quantify features of PPAOS that are distinct from those associated with PPA in which AOS is not present.