Conduction aphasia, syntactic alexia, and the anatomy of syntactic comprehension

Syntactic alexia is the inability to comprehend graphically presented sentences when the meaning depends on syntax. Although previously described in association with Broca's aphasia and attributed solely to the frontal lobe portion of the lesions, syntactic alexia has not been reported to accompany conduction aphasia. We studied three patients who had conduction aphasia from temporoparietal lesions and syntactic alexia. None of them had lesions in Broca's area. Broca's aphasics and our patients with conduction aphasia have a syntactic comprehension disturbance. Since Broca's aphasics and our patients have lesions that may extend into the supramarginal gyrus, we postulate that this area may be critical for comprehending syntax.