Objectives: The ability to calculate, which is an important aspect of social daily living, is commonly impaired in patients with Alzheimer's disease even early in the course of the disease. Dyscalculia is often accompanied by focal brain damage, and has been argued to be an independent sign localised around the left temporoparietal region. However, the region most responsible for dyscalculia in Alzheimer's disease has not been determined. The relation between calculation ability and regional cerebral glucose metabolism in Alzheimer's disease was therefore examined.
Methods: The calculation ability, In 91 patients with probable Alzheimer's disease of minimal to moderate severity, was assessed using the arithmetic subtest of the Wechsler adult intelligence scale-revised and the performance correlated with regional cerebral glucose metabolism determined by "F-fluorodeoxyglucose and PET.
Results: Regional glucose metabolism in the left inferior parietal lobule and in the left inferior temporal gyrus was significantly correlated with the calculation performance irrespective of age, sex, education, and severity of disease.
Conclusions: The results suggest that dysfunction of the left inferior parietal lobule and the left inferior temporal gyrus plays an important part in producing dyscalculia in patients with Alzheimer's disease.