Thalamic aphasia. A conceptional critique.

Four patients with aphasia due to small circumscribed thalamic lesions are presented. A review of the literature on thalamic aphasia revealed 16 similar cases. While the general consensus that only left-sided thalmic lesions are associated with aphasia is confirmed, analysis of the sites of the thalamic infarctions and the dysphasia elements did not reveal an unequivocal correlation. The explanation of this finding is that (a) disruption of any circuit, whether taking place in the connections or in the nuclei, leads to dysfunction and (b) thalamofrontal connections are not topographically arranged according to the thalamic nuclei, but show a frontal rostrocaudal/thalamic mediolateral interrelationship irrespective of thalamic nuclear masses.