Spinal cord injury tends to be permanent, sudden, and profoundly life-altering. Three out of four people in wheelchairs are men or boys, victims of male attraction to fast cars, motorcycles, sports, and a propensity to engage in violence. The initial death of neurons and oligodendrocytes results from the blow to the spinal cord that sheared open cells, and to the release of neurotransmitters (e.g., glutamate) spilled in topic levels from damaged neurons. The disrupted blood flow from vascular damage kills other cells, as well. A second wave of cell death results from toxic conditions in the damaged region caused by microglia and astrocytes battling the injury. There are no Schwann cells to help with repair as there are in the peripheral nervous system. (Fields, R. Douglas, PhD. The Other Brain. p 80-90. NY: Simon & Schuster, 2009.)