Objective. Neurofibromatosis type 1 (NF1) is a rare autosomal dominant single-gene disorder, primarily characterized by multiple (sub)cutaneous neurofibromas and café-au-lait macules. The cognitive...Show moreObjective. Neurofibromatosis type 1 (NF1) is a rare autosomal dominant single-gene disorder, primarily characterized by multiple (sub)cutaneous neurofibromas and café-au-lait macules. The cognitive profile of children with NF1 is hypothesised to be associated with deficits in three domains; visuospatial ability, executive function, learning and their interdependency. Between ages 11 and 15 years, an increase in PIQ was found in children with NF1. Because visuospatial abilities are strongly related to the level of PIQ as measured with the WISC-III-NL, the objective of this study was to find if improvement in visuospatial abilities in this course of age predicts this progress in PIQ. Methods. In a longitudinal design, 31 children with NF1 were assessed with the WISC-III-NL and a standardised battery of neuropsychological assessments at average age 11 and 15. In the statistical analyses the scores on the subtests of the WISC-III-NL constituting PIQ at age 11 and 15 were compared with paired t-tests and a repeated measures ANOVA. Next, five multivariable linear regression analyses were conducted with the increase in PIQ as the dependent variable and five neuropsychological constructs (visual and auditory attention, visuospatial ability, processing speed and fine motor skills) as the predictors. Results. Picture arrangement was the only WISC-III-NL subtest to increase between age 11 and 15, d = 1.04, p < .001. The repeated measures ANOVA resulted in a difference in improvement between the five WISC-III-NL subtest scores, p < .001. Visuospatial ability was the only neuropsychological construct that predicted the increase in PIQ, b = 1.22, p = .005. There was no correlation between improvement in picture arrangement and improvement in visuospatial ability. Conclusions. Improvement in visuospatial ability appears to predict increase in PIQ in children with NF1 between age 11 and 15. Further investigation is required to determine if these findings are replicable in larger sample sizes. Additionally, there is further research needed to explore variances in the amount of improvement observed across different visuospatial tasks. It may be possible that progress in executive function effects improvement in some visuospatial tasks. Implications are that executive functioning must be taken into account when interpreting (visuospatial) results from neuropsychological assessments in children with NF1, both in science and in the clinic.Show less