Studies have found that CRS can not only reduce the number and density of hippocampal dendritic spines but also reduce the expression levels of the presynaptic membrane marker synaptophysin, the postsynaptic membrane marker post-synaptic density-95 (PSD-95), and the neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF) [51-53] (Fig. 4). This evidence concerns the gene BDNF and congenital rubella syndrome.