Spinal cord injury can interrupt the sympathetic and parasympathetic pathways that are essential to erectile function. Hormone deficiency may account for a small percentage of ED cases. Testosterone, LH, and prolactin levels can be assessed. To best understand ED, it is helpful to first understand the anatomy and physiology of a normal erection. Understanding how the normal erection occurs dramatically changed the way ED is treated today.
Erections are the result of a neurovascular event triggered by cognitive or tactile stimulation.
An erection begins with a tactile or psychogenic stimulus that is processed in the brain. Sympathetic and parasympathetic impulses from the spinal cord contribute to smooth muscle relaxation and the inflow of blood. Chemical mediators are used to cause the essential relaxation of tissue and perfusion of the erectile cylinders. The erection occurs because of the engorgement within the corposa cavernosa. The corpus spongiosum contains the urethra.