White matter integrity and cognitive performance in children with prenatal methamphetamine exposure

There is emerging evidence on the harmful effects of prenatal methamphetamine (MA) exposure on the structure and function of the developing brain. However, few studies have assessed white matter structural integrity in the presence of prenatal MA exposure, and results are inconsistent. This investigation thus used diffusion tensor imaging (DTI) to investigate white matter microstructure and cognitive performance in a group of prenatal MA exposed (or MA) children and controls of similar age. Seventeen MA children and 15 healthy controls (aged 6-7 years) underwent DTI and assessment of motor function and general cognitive ability. Whole brain analyses of white matter structure were performed using FSL's tract-based spatial statistics comparing fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD). Mean diffusion values were extracted from white matter regions shown to differ across groups to determine whether variations in FA predicted cognitive performance. Analyses were controlled for maternal nicotine use. MA children showed significantly lower FA as well as higher MD, RD and AD in tracts that traverse striatal, limbic and frontal regions. Abnormal FA levels in MA children were significantly associated with poorer motor coordination and general cognitive ability sub-items that relate to aspects of executive function. Our findings suggest that, consistent with previous studies in older children, there are disruptions of white matter microstructural integrity in striatal, limbic and frontal regions of young MA exposed children, with prominent cognitive implications. Future longitudinal studies may clarify how prenatal MA exposure affects white matter structural connectivity at different stages of brain maturation.