Dysarthria of adult cerebral palsy: II. Phonemic analysis of articulation errors

The articulation errors of 32 spastic and 18 athetoid males, aged 17-55 years, were analyzed using a confusion matrix paradigm. The subjects had a diagnosis of congenital cerebral palsy, and adequate intelligence, hearing, and ability to perform the speech task. Phonetic transcriptions were made of single-word utterances which contained 49 selected phonemes: 22 word-initial consonants, 18 word-final consonants and nine vowels. Errors of substitution, omission and distortion were categorized on confusion matrices such that patterns could be observed. It was found that within-manner errors (place or voicing errors or both) exceeded between-manner errors by a substantial amount, more so on final consonants. The predominant within-manner errors occurred on fricative phonemes for both initial and final positions. Affricate within-manner errors, all of devoicing, were also frequent in final position. The predominant between-manner initial position errors involved liquid-to-glide and affricate-to-stop changes, and for final position, affricate-to-fricative. Phoneme omission occurred three times more frequently on final than on initial consonants. The error data of individual subjects were found to correspond with the identified overall group patterns. Those with markedly reduced speech intelligibility demonstrated the same patterns of error as the overall group. The implications for treatment are discussed.