Dysarthria of adult cerebral palsy: I. Intelligibility and articulatory impairment.

The speech intelligibility and articulatory impairment of 32 spastic and 18 athetoid males, aged 17-55, were examined. Selection was based on a definite diagnosis of cerebral palsy, and adequate intelligence, hearing, and ability to perform the required tasks. Two estimates of speech intelligibility were obtained from naive listeners: single words correctly recognized and prose intelligibility rating. Diadochokinetic (DDK) syllable rates and percent correct articulation of selected phonemes were employed as indices of articulatory impairment. The 50 subjects were, on average, judged to be 50% intelligible on both intelligibility estimates. Group mean DDK rate was 2.9 syllables per second and 78% of phonemes were transcribed as correctly articulated. :The mean scores of the spastic subjects were superior to the athetoids on all speech measures, significantly so for single-word intelligibility and DDK rate even when group inequalities for physical disability and I.Q. were adjusted. In this sample, spastics were less physically disabled and had lower I.Q.'s than athetoids. Specific phonemic features characteristic of the dysarthria in cerebral-palsied subjects were: (1) anterior lingual place inaccuracy; (2) reduced precision of fricative and affricate manners; and (3) inability to achieve the extreme positions in the vowel articulatory space. A comparison of these results with those reported for children with cerebral palsy suggests that the consonantal place and manner problems are fairly stable features of cerebral palsy dysarthria.