Neuropsychological differentiation of subnormal arithmetic abilities in children.
For the neuropsychological diagnosis of a Specific disorder of arithmetic skills the standard is defined worldwide by the diagnostic guidelines of the two major classification systems of psychiatric disorders, the ICD- 10 and the DSM-IV, both of which use the discrepancy criterion as the key feature of the diagnosis. It becomes clear that following such guidelines can only mean an extensive diagnostic assessment of patients with subnormal arithmetic abilities, including the social and previous medical history followed by the exclusion of a present disorder or disability, often necessitating laboratory, neuroimaging and neurophysiological tests. In the neuropsychological diagnosis of a Specific disorder of arithmetical skills we found a stepwise approach including previously obtained test results to be most practical and economical. The assessment instruments such as intelligence tests, neuropsychological test batteries, academic achievement tests, specific neuropsychological tests, test batteries for arithmetic abilities or error analysis are discussed. An overview of case studies in the literature is given; however, the overwhelming majority of case reports on patients with arithmetic disabilities are casuistics of adult patients with an acquired loss of arithmetic abilities. The importance of a differentiated neuropsychological diagnosis is demonstrated by four of our own cases: of borderline deficient intelligence, a combined disorder of academic skills, congenital brain dysfunction, and a specific disorder of arithmetic skills. Especially the new quality in assessing arithmetic abilities with the NUCALC battery is demonstrated; diagnostic and therapeutic consequences are discussed.