Relationship between the corpus callosum and neurocognitive disabilities in children with NF-1: diffusion tensor imaging features.

Mild neurocognitive disabilities are commonly observed in children with neurofibromatosis type 1 (NF-1). Enlargement of the corpus callosum (CC) is one of the findings in NF-1, but the pathogenesis has not yet been clarified. In this study, we investigated whether diffusion tensor imaging (DTI) features of CC differed between children with NF-1 and healthy control subjects, and we tried to evaluate the association between the microstructural integrity of CC and neurocognitive disabilities, based on apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values. The study population consisted of 37 children with NF-1 and 31 healthy controls. Midsagittal CC surface area measurements were obtained from volumetric sagittal T1-weighted turbo spin echo images. FA and ADC values were obtained from the genu and splenium of CC. The results were compared to that of controls. The correlations between neurocognitive test results and measurements of ADC, FA, and surface areas of midsagittal CC in NF-1 patients were investigated. Total CC area in children with NF-1 was significantly larger than healthy controls. ADC values obtained from the genu of CC were significantly higher in NF-1 children. A negative correlation was observed between the ADC values of the genu of the CC and the arithmetic and digit span scores and between the FA values of the genu and coding scores in children with NF-1. The DTI changes in the genu of CC in children with NF-1 may indicate subtle structural damage, although conventional MRI is normal. ADC and FA changes in the genu may be due to loss of axonal integrity and vasogenic-like edema in the axons responsible for some intellectual functions. DTI may help clarify the underlying pathophysiology of CC changes in relation to neurocognitive function disorders in children with NF1.