[Reading and writing deficit in cases of localized infarction of the left anterior thalamus]

We have observed two cases with marked reading and writing deficits, in which speech and oral comprehension were generally intact. Detailed symptomatological study was performed on these cases, and the lesions were examined organically (X-ray computed tomography [X-ray CT], magnetic resonance imaging [MRI] and functionally (positron emission tomography [PET]. In addition to the marked reading and writing deficits, mild naming and memory disorders were found. X-ray CT and MRI revealed that the lesions were limited to the regions fed by the polar and paramedian arteries in the left thalamus. In one case, PET demonstrated a functional disturbance of the left parietal and temporal lobes in addition to the left thalamus. Most previous cases have shown lesions in the anterior portion of the thalamus. It is possible that the reading and writing deficits in these cases may be due to the thalamic lesion itself, but the PET findings strongly suggest that a secondary cortical lesion may be involved in producing the higher cognitive disorders.