For a long time, it was assumed that the cause of ac alculia was damage to the left hemisphere of the brain. Subsequently, suspicions were raised that the cause was also damage to the right cerebral hemisphere. Today, it is known that both hemispheres may be responsible for the disorder as they are responsible for the processes of counting, analysing and reading. The cause of acalculia can be a result of different types of mechanical damage to the brain, as well as those resulting from ongoing or past brain diseases (brain Guy, multiple sclerosis, strokes and many others).

The affected person does not have the ability to perform any tasks on numbers, nor to a large extent on writing (addition, subtraction, multiplication or division). When he or she has to perform a calculus task by ear he or she usually does so correctly without much difficulty. In addition, people with acalculia develop problems with concentration, memory or memorisation.

It is a disease that causes many problems in everyday life, especially in matters related to paying bills, finding the right house number, writing a telephone number, remembering it or repeating it. The person with the illness requires the assistance of a third person.

Diagnosis of the disease is very easy; most often the patient goes to a neurologist or neuropsychologist. There, a test is carried out, which involves the person suffering from acalkulia writing down the numbers they have heard or performing a very simple mathematical task. The written task will be done incorrectly, but verbally in most cases the patient will give the correct answer. A quick diagnosis makes it possible to start rehabilitation.

This is adapted individually to each patient, taking into account the cause of the acalculia. It involves practising, writing down, repeating tasks on numbers. It requires patience, calmness, composure and commitment on the part of the patient and the rehabilitation therapist.