Control of upper airway structures during nonspeech tasks in normal and cerebral-palsied subjects: EMG findings.

Electromyographic (EMG) recordings taken from 13 orofacial and mandibular muscles during a sequence of nonspeech movements were compared in six normal and six cerebral-palsied adult subjects. Abnormalities in the amplitude of muscle activity and timing of muscle control in the cerebral-palsied subjects were borne out in statistically significant differences between the two subject groups on five measures of muscle activity. The findings do not support hypotheses that weakness affects individual upper airway muscles in cerebral-palsied persons or that a pathological imbalance between positive and negative oral reactions is present in these subjects. A possible mechanism for hypertonicity in facial muscles in cerebral palsy is suggested, based on inappropriate activation patterns across muscles. The results are consistent with a previous proposal that a defect in the specification of motor commands and/or their communication to muscles is a fundamental abnormality in cerebral-palsied individuals which affects both speech and nonspeech motor control.