Researchers believe that, during the first week after cerebral ischemia, there is a collection of toxins and glutamate neurotransmitter and free radicals in the injured area of the brain and after 7 days these toxins are removed and the area is prepared to receive any new treatment (stem cells, growth factors, neurotrophins, etc.)[36, 37]. This evidence concerns the gene BDNF and brain ischemia.