Saturday, June 28, 2008

Isolation of the speech area*


The case is presented of a 22 year-old woman who survived ten years following an episode of carbon-monoxide poisoning. The patient's language behavior presented several striking clinical features. Her spontaneous speech was confined to a few stereotyped phrases and she gave no evidence of comprehension of language. By contrast she exhibited echolalic repetition with excellent articulation. In many instances she showed the “completion” phenomenon described by Stengel, i.e. the completion of stereotyped or simple phrases uttered by the examiner. In addition she was able to carry on verbal learning as shown by her ability to learn the words (as well as music) of songs which had not existed before her illness.

At post-mortem, a detailed study of serial whole-brain sections showed intactness of auditory pathways up to and including Heschl's gyrus, of Wernicke's area and Broca's area and of the arcuate fasciculus connecting these two cortical regions, of the lower Rolandic cortex and of corresponding portions of the pyramidal tract. The hippocampal region (except for Sommer's sector) and the structures of the limbic system were well preserved, as was the reticular substance of the brain stem.

This case corresponds in its clinical picture to the classical “mixed transcortical aphasia” (i.e. paucity of speech and severe comprehension deficits with excellent preservation of repetition) with some new features (capacity for verbal learning) not previously described. The pathology agrees with that advanced by Goldstein for this condition, i.e. “isolation of the speech area”. The explanation advanced for this clinical picture is that comprehension and propositional speech are lost because of the isolation of the speech region from other cortical areas, while those functions which can be carried on by the speech area itself, i.e. repetition and completion of well-learned phrases, are preserved. The ability to carry on verbal learning in this patient probably depended on the intactness of the medial temporal regions and the preservation of the connections to them from Wernicke's area.