Mutism: loss of neocortical and limbic vocalization.

A patient with complete mutism of 5 years duration was studied to determine the cause of the defective phonation. The patient had neurological findings indicative of pseudobulbar palsy, but he had lost emotional vocalization and emotional facial expression, as well as propositional speech. Phylogenetic, ontogenetic, and anatomic evidence indicates that propositional speech and volitional facial movements are mediated by corticobulbar tracts descending from neocortical areas, whereas emotional vocalization and emotional facial expression are dependent on intact limbic system connections. The findings suggest that the patient's impaired faciovocal expression was the result of lesions involving both limbic system and descending neocortical connections.