Calculation deficits in patients with right and left hemisphere damage.

Calculation abilities were studied in 41 left and 21 right hemisphere damaged patients. Their results were compared with a normal group matched by age, sex and educational level. Left hemisphere patients were grouped according to the type of accompanying aphasia. All patient groups presented at least a certain degree of acalculia. However, maximum difficulties were found in retrorolandic left hemisphere patients. Right hemisphere patients, especially retrorolandic patients, also presented impairments in calculation abilities, resulting mainly from spatial defects. Different types of errors were analyzed. Observed errors may be similar, but due to highly different neuropsychological dysfunctioning. Primary and secondary observed defects may be attributed to a diverse array of underlying deficits.