Congenital bilateral perisylvian syndrome(CBPS) is a recently described disease entity characterized by pseudobulbar palsy, dysarthria, epilepsy, mental retardation, and dysplastic lesions in the bilateral perisylvian area on MRI.

Dysarthria is a striking clinical manifestation of this syndrome and recognition of specific pattern of dysarthria, therefore, is very important in diagnosing this disease entity. We investigated the acoustic, aerodynamic, and electrophysiologic characteristics of dysarthria in 9 patients with CBPS using computerized speech laboratory, Visi-Pitch, Aerophone II, Nasometer, and multichannel dynamic electromyography.

In the patients with CBPS, frequency of first and second formants(F1 & F2) of vowel /i, u, o/ and F1 of /e/ were distorted. Breakdown of formant structure and breathiness were also visualized in wide and narrow band spectrogram. The voice onset time, total duration of meaningless three syllables were significantly prolonged, especially for velar and lateral consonants, and diadochokinetic rate was decreased in comparision with normal controls, reflecting disturbance of oral motor control. Aerodynamic study revealed that patients with CBPS had significantly lower mean and peak air flow for stop consonants, which indicate difficulties to maintain the tension of vocal fold during aspiration and phonation. Nasalance was markdly increased as well. Multichannel dynamic electromyography of genioglossus, cricothyroid, and orbicularis oris muscles was carried out in 6 out of 9 patients. This analysis showed weakness of muscle activity in two patients, sustained contractions in other two patients, and combined features in the remaing two patients.

It is concluded that involvement of tongue muscles is the most responsible for dysarthria in patients with CBPS. In addition, velopharyngeal and laryngeal muscles are also contributing in creating dysarthria. The quantitative and qualitative analysis of dysarthria in acoustic, aerodynamic, and electrophysiologic aspects enabled us to understand the underlying pathophysiology, to differentiate it from other types of dysarthria caused by other neurological diseases, and to estimate the efficacy of rehabilitative treatment in patients with CBPS.