Aim: To describe the cortical brain development and full-IQ performance in middle school age children after extremely preterm (EPT) birth considering discrete white matter abnormalities (WMA). In addition, to assess possible early motor predictors of cortical brain development and full-IQ in children born EPT with and without discrete WMA diagnosed at 10 years. Methods: T1-weighted MRI images from fifty-one children born before 27 weeks' gestation and 40 full-term born controls (Mage=10.09 years; SDage=0.77) were scored for discrete WMA and analyzed with Freesurfer (v7.2.0). The assessments included motor assessments (i.e., fine- and gross motor function) of Bayley Scales of Infant and Toddler Development - Third Edition (BSID-III) at a mean age of 2 1/2 years. Full-IQ was also assessed with Wechsler Intelligence Scale for Children - Fifth Edition (WISC-V) at 12 years. Results: No differences were displayed in motor function or full-IQ score between children born EPT with and without discrete WMA at 10 years. Moreover, no global differences were found in cortex volume. However, bilateral mean cortical thicknesses (CTh) were exhibited to be thicker in children born EPT with discrete WMA. Children born EPT with discrete WMA exhibited regional increases mainly in the frontal and temporal lobes apart from left caudal anterior cingulate gyrus (mean difference = -0.11 (-0.22, -0.01), p = 0.026). Full-IQ was predicted by impairments in fine motor skills in children born EPT with discrete WMA, explaining 42.9% of the variance. Conclusions: Bilateral mean and regional CTh were found to be greater in children born EPT with discrete WMA at 10 years compared to those without. Fine motor function at 2 1/2 years was a strong predictor of full-IQ dependent in children with discrete WMA.