Proton MRS was performed in a patient with developmental acalculia. The res
ults indicated a focal, wedge-shaped defect in the left temporoparietal bra
in region near the angular gyrus, with differential decreases in N-acetyl-a
spartate, creatine, and choline, These results support the hypothesis that
developmental acalculia, like acquired acalculia, is associated with left p
osterior hemisphere lesions.