Vowel Formant Dispersion Reflects Severity of Apraxia of Speech.
Dirk-Bart den Ouden, Elena Galkina, Alexandra Basilakos and 1 others
PMID 30297975WHAT IT FOUND
After stroke, greater variability in vowel sounds and voiced stop timing during picture description went with more severe apraxia of speech, but acoustic measures alone were not accurate enough for diagnosis.
Key findings
01Speakers with AOS showed greater variability in first and second vowel formants than unimpaired speakers or speakers with aphasia only.
02AOS severity was predicted by variability in first and second vowel formants and voiced-stop timing; shorter voiceless-stop timing also predicted more severe AOS.
03The acoustic measures classified AOS better than chance, but not well enough to rely on them alone for diagnosis.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The analysed sample was 53 stroke survivors, and only 20 had AOS, so results may not generalise to all people with apraxia of speech. Four of 57 participants were excluded because vowels could not be reliably identified, so very unclear speech may be underrepresented. The groups were not balanced by gender, and gender affected some timing and formant values, although the authors say this did not appear to drive the main outcomes. The classification accuracies varied by comparison, and the authors state these measures are not sufficient alone for diagnosis. Dysarthria findings came from only 8 speakers, and 6 of 8 dysarthric speakers were also diagnosed with AOS, so the dysarthria result is exploratory. The correlations were tested without correction for multiple comparisons, and several discriminant analyses were run, so some findings are exploratory. Vowel boundary marking was done by one author, with a second author checking only 100 trials.
Declared interests
No conflict of interest was declared by the authors.
The easy way to misread this
Do not conclude that acoustic measures can diagnose apraxia of speech. The three-way classification was correct in only 60.4% of cases, and the authors state these measures are not sufficient to rely on alone.