Spatial Acalculia
Spatial acalculia is most often associated with right cerebral hemisphere pathology (Ardila and Rosselli, 1994). Also, spatial acalculia is generally correlated with hemineglect, topographic agnosia, constructional apraxia and generic spatial deficits. These patients lack the ability to write numbers correctly. Therefore, it is understandable that they perform significantly better in orally presented mathematics than written ones. They exclusively use the right side of the page and make repetition errors (eg, 11 is written as 111), are unable to maintain a straight line and have obvious spatial disorganization. The spatial disorganization includes very poor alignment of columns and confusion about where to find the "carried" value in written problems. In left neglect patients there may even be failure to complete the operation or be unable to read the numerical sign (that is usually on the left). Also, they have trouble trying to remembering multiplication tables and may have the knowledge of the appropriate steps to take in multiplication problems but are unable to place the quantities (Grana et al., 2006, see case study of patient PN). Furthermore, these patients often mix operations when performing mathematical problems (eg, subtract when you are supposed to add). (Ardila, 2008)
