Functional MRI of visual-spatial processing in neurofibromatosis, type I.

Visual-spatial impairment and neuroanatomical abnormalities are considered hallmark features of neurofibromatosis, type I (NF-I). Numerous studies have demonstrated visual-spatial deficits in children with NF-I, but few relations between these deficits and neuroanatomical abnormalities have been identified. We compared the functional neuroanatomy of cerebral regions involved in the spatial transformation of alphanumeric stimuli in individuals with NF-I and healthy control participants using functional magnetic resonance imaging (fMRI). Given the prevalence of visual pathway abnormalities and visual-spatial deficits in NF-I, we hypothesized that less neuronal hemodynamic activity would be found in occipital and parietal cortices in this group compared with controls. However, NF-I participants relied to a greater degree than controls on posterior cortex (including occipital, parietal, and middle temporal cortices) relative to lateral and inferior frontal regions during visual-spatial analysis. This pattern was significantly related to their behavioral performance on the fMRI task, which in turn was also positively correlated with reading scores. These findings support evidence of frontal cortical anomalies in NF-I and may provide a pathophysiological basis for cognitive deficits in NF-I.