Figure Caption: Lesions in the region of the angular and marginal gyri commonly result in disturbance of arithmetic.

Acalculia: Inability to perform mathematical computations.

Both language and arithmetic are logical, generative systems in which elements are combined by rules to produce statements. In addition, both systems use the same logic and all statements in arithmetic are statements of language.

Brain lesions that cause receptive or Wernicke's aphasia are often associated with impairment of the ability to solve arithmetic problems. Although aphasia and acalculia often are associated, acalculia may exist independently. Calculation errors consist of substitution of one operation for another (e.g., the patient may subtract when requested to add numbers), count numbers instead of correctly operating in them (e.g., 3 + 4 = 5), perseveration of numbers (e.g., 2 x 4 = 44), simple combinations of numbers rather than operating in them (e.g., 5 + 3 = 53). Left parietal lobe lesions commonly result in acalculia.

Assessment

Calculation impairment is assessed by requesting the patient to perform arithmetic problems requiring simple operations, such as addition and subtraction. If the patient is able to perform these operations then standardized achievement tests may be used to assess arithmetic at more complex levels. Word problems, and problems using concepts from algebra are examples of mathematical knowledge and ability requred at this higher level.