[Acalculia: its classification, aetiology and clinical management]

To carry out a review of the literature on the different neurological mechanisms involved in processing calculations, the injuries to brain structure that can result in acalculia and the clinical management of these patients. Development and conclusions. Acalculia is defined as the disorder affecting the ability to calculate that is acquired as the result of a brain injury. Despite being a frequent symptom and its association to numerous systemic and neurological diseases, no clear study protocol exists due to the fact that, first, it is usually accompanied by other, more important neurological symptoms and, second, it occurs in a very heterogeneous population, where clear differences can be seen according to the sociocultural level of the patient. Acalculia has been associated both to general alterations of the central nervous system and to others affecting local structures. Perhaps the most striking example of the former is the case of dementias, where it has even been suggested that it could be an early sign of Alzheimer's disease. With respect to the latter, the most notable are those affecting the left parietal lobe. In this article the following are discussed: 1) the different classifications that have been developed for the loss of the ability to calculate; 2) the involvement of the different structures of the nervous system in numeric processing, based on the associated structural lesions and on studies that have been conducted using functional tests and brain imaging; and 3) the different neuropsychological instruments that are available to study this capacity.