Automatic Speech Recognition and Phonetics-Informed Sentence Design for Spastic Dysarthria Detection and Corticobulbar Lesion Localization

Spastic dysarthria diagnosis through subjective neurologist auditory-perceptual assessment remains standard practice despite known inaccuracy. To address this gap, we developed an objective framework grounded in phonetic evidence that spastic dysarthria preferentially impairs initial consonant articulation, using automatic speech recognition (ASR) to quantify dysarthria and localize corticobulbar lesions. We created four reading sentences targeting groups of initial consonants: labial (facial), lingual-alveolar (tongue), and velopharyngeal (pharyngeal/soft-palate) sentence, along with a mixed-consonant sentence for comparative evaluation. Thirty-seven patients with neuroimaging-confirmed corticobulbar lesions and 37 controls read each sentence. ASR transcribed dysarthric speech into text, and we computed a "syllable-error score" by counting incorrectly transcribed syllables. This yields a clinically meaningful feature that makes syllable-level phonetic errors explicit. Logistic regression models were trained for each sentence, and performance was summarized by the area under the receiver operating characteristic curve (AUC) across 10,000 resampled train-test splits. Consonant-specific sentences significantly outperformed the mixed sentence: the lingual-alveolar sentence performed best with (median AUC 0.88), followed by the labial (0.80), then the velopharyngeal sentence (0.72), while the mixed-consonant sentence was lowest (0.67). These results suggest that the interpretable ASR-derived syllable error feature, combined with a relevant machine learning classifier could inform clinical insight into consonant-specific vulnerability in spastic dysarthria, with lingual-alveolar consonants appearing particularly informative. Overall, this novel ASR-based framework, together with phonetics-informed feature design provides objective, accurate, and clinically meaningful digital quantification for spastic dysarthria detection and corticobulbar lesion localization.