Background: Cerebellar mutism syndrome (CMS) occurs in approximately one-fourth to one-third of children who have undergone posterior fossa surgery. As the mutism resolves, speech has a characteristic slow rate, monopitch and low intensity. In view of developing a targeted rehabilitation approach for Chinese-speaking children with CMS dysarthria, we carried out preliminary perceptual and acoustic analyses of children’s speech from a standardized clinical battery.

Methods: 24 children slated to undergo posterior fossa surgery at Beijing Children’s Hospital were recruited for this study. All children completed a clinical assessment of neuromotor control, speech and language production. Data from 18 participants was available at follow-up, including 6 recovering from post-operative CMS (age range 7-12 years) and 12 whose speech remained unaffected (age range 4-14 years). Auditory-perceptual and acoustic analyses were carried out on all speech data.

Results:
Perceptual analyses support impressions of a primary ataxic dysarthria that may include spastic or flaccid dimensions in more severe cases. The speech ataxia was characterized by prosodic excess (e.g. slow rate, prolonged phonemes, excess and equal stress), phonatory-prosodic insufficiency and articulatory inaccuracy. Severity of involvement of different speech subsystems was highly variable across cases. Prosodic excess was associated with an appreciable incoordination of respiratory support for speech. Correlate acoustic measures corroborated these findings, including reduced breath group/phonation time (≥ -3s, vs. + 0.5s among non-CMS cases; p < 0.05), increased segmental and syllabic durations (≥ +150ms vs. 0.3s; p < 0.05), and a low pairwise variability index (~20 vs. 30 in non-CMS cases; p < 0.05).

Discussion:
This perceptual and acoustic analysis of dysarthric characteristics post-CMS confers a primary prosodic dimension to the disorder. Results indicate a potential characteristic respiratory-phonatory incoordination that warrants closer evaluation and focus for therapy in sub-acute stages of this speech disorder.
Keywords : Cerebellar mustim syndrome, Motor speech disorder, Speech acoustics