Are there specific disabilities of number processing in adolescent patients with Anorexia nervosa? Evidence from clinical and neuropsychological datawhen compared to morphometric measures from magnetic resonance imaging

The cerebral effect of the loss of body weight in Anorexia nervosa (A.n.) - the so - called 'pseudoatrophy' - is well known and confirmed by several n euroimaging studies. Another subject of intensive research has been whether A.n. leads to specific cognitive impairments, especially of intelligence. However, there are no previous studies on the relations between the cerebra l changes, intelligence performance, and disorders of number processing in adolescent patients with A.n. We examined n = 18 inpatients with A.n. (mean s at admission: age 14.5 years, SD 1.59; BMI 14.9, SD 1.36), diagnosed acco rding to ICD-IO criteria at three different timepoints: at admission to tre atment (T-1), with 50 % restoration of their normal weight (T-2), and with normal weight (T-3). At each timepoint, a cerebral MRI scan was obtained. B ased on the MRI we determined the volume of the external and internal cereb rospinal fluid cavities, fissures of Sylvius, the surface of mesencephalon and pens, and surface and length of the Corpus callosum. At T-1 and T-3, a neuropsychological examination was conducted including tests of the general fluid ability and general cristallized ability of intelligence (CFT-20), a s well as tests of vocabulary and number processing. The same instruments w ere given to a group of matched controls (means: age 15.8 years, SD 1.57; B MI 20.5, SD 2.3) at one timepoint. We could show a significant volume diffe rence of the lateral ventricles and the fissure of Sylvius between patients at T-1 and controls, which abaded with the patient's weight restoration. B ut a significant surface deficit of the mesencephalon, and less pronounced in the pens, persisted to T-3 in patients when compared to controls, sugges ting a selectivity of the cerebral changes in A.n. The neuropsychological e xaminations revealed significant changes in test performance for both the g eneral intelligence test and number processing. At T-1 the number processin g performance was significantly lower in patients when compared to controls . However, when the patients had restored their normal body weight, we foun d 2.02 % with a 'severe disorder of arithmetic skills' and 4.45 % with a 'f unctional disorder of arithmetic skills'. This combined prevalence of 6.47 % of patients with a subnormal arithmetic performance is analogous to that in the normal population.