Congenital bilateral perisylvian syndrome(CBPS) is a recently described entity diagnosed on the bases of neuroimaging and speech abnormality. All patients have severe orofacial paresis, moderate to severe dysarthria and bilateral and bilateral perisylvian dysplasia. Dysarthria is a striking clinical manifestation of this syndrome and the recognition of specific pattern of dysarthria has the diagnostic significance of this unique syndrome.

We evaluated the acoustic characteristics of dysarthria in 4 CBPS patients who were diagnosed by magnetic resonance imaging(MRI) scanning using digital computerized spectrograph, Visi-Pitch^Ⱂ and Nasometer^Ⱂ.

In the spectrographic analysis, loss of specific characteristics of formants of vowels and increment of noise in the high frequency regions were observed. The voice onset time(VOT) was prolonged in the bilabial and alveolar stop consonants. Total duration of meaningless words containing two syllables were increased as well. In the Visi-Pitch^Ⱂ analysis, mono-pitch and mono-loudness were characterized and diadochokinetic rate was decreased. Nasalance was increased and the slope of nasalance was flat in CBPS patients in comparison with normal subjects.

These findings are reflection of the impairment of facial motor area in the primary motor cortex, which results in altered movement of tongue, lips and velopharynx. The recognition and objective evaluation of the acoustic characteristics of dysarthria in the these patients can give a clue for the diagnosis of this syndrome.