Abstract: Background The diagnostic utility of magnetic resonance (MR) diffusion tensor imaging (DTI) in the diagnosis of cortical and white matter lesions in children with focal cortical dysplasia (FCD) is unclear. Objective To evaluate the value of conventional MR and DTI in the diagnosis of FCD in children. Design The children with unilateral temporal lobe FCD confirmed by surgery and pathology were taken as the research objects, and the contralateral side of FCD and healthy children were taken as the control group. DTI parameters were compared in two groups. Methods The onset age and disease course of FCD and MR and DTI data of healthy children who have matched time of MR examination, age and gender were collected. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of cortical and white matter of typical lesions on the affected and contralateral sides of FCD and in healthy children were measured. Main outcome measures AUC of ROC curve of DTI parameters on the affected and contralateral sides of FCD and in healthy children. Results There were 21 cases of FCD with an average age of 8.2 (1-16) years, an average age of 4.5 (1-8) years, an average course of disease of 5.8 (1-9) years, and 20 cases of healthy children with an average age of 7.9 (2-16) years. FA values of the affected cortex and white matter were significantly lower than those of the corresponding areas of the contralateral side and healthy chidren (P=0.029, 0.014, 0.018 and 0.007 respectively). ADC values of the affected cortex were significantly higher than those of the corresponding areas of the contralateral side and healthy children (P=0.001). ADC values of the affected white matter were not significantly different from those of the corresponding areas of the contralateral side and healthy children (P> 0.05). AUC of ROC curve of DTI parameters in FCD children compared with corresponding areas in healthy children was all larger than that of corresponding DTI parameters in comparison of two sides in children with FCD. The ADC value of the cortical area in the case group was positively correlated with the course of disease (r=0.762, P=0.013). The FA value in the white matter area was negatively correlated with the course of disease (r=-0.694, P=0.025), and positively correlated with the age of onset (r=0.705, P=0.017). Conclusion DTI parameters can reflect the microstructural differences among the affected side of FCD, the contralateral side of FCD and healthy children. Correlation of clinical factors can also be reflected. The comparison of the affected side of FCD and the corresponding areas in healthy children has high quality diagnostic utility, which is more significant than the comparison of the affected and contralateral sides of FCD under the same parameters. Therefore, it is of great significance to try to establish the reference values of FA (cortex and white matter) and ADC (cortex and white matter) in normal population.

Key words: Magnetic resonance imaging, Diffusion tensor imaging, Focal cortical dysplasia, Temporal lobe, Children