Most Parkinson's sufferers are over sixty, and in men of this age, non-Parkinson's related causes are usually responsible for their erectile dysfunction. Of the one million patients with Parkinson's in the U.S. today, approximately 600,000 are men, of which some 200,000 have erectile dysfunction. Without question, diabetes is the single greatest cause of neurogenic erectile dysfunction. Because an erection is a neurovascular event, any disease or trauma that affects the brain, spinal cord, penile nerve supply, or the receptors in the small arteries and cavernous smooth muscle of the penis can lead to impotence. This is yet another reason why one shouldn't smoke in bed, or if one hopes to get into bed.

Again, the net effect is the same - not enough clamping of the penile veins to allow for the heightened intracavernous arterial pressures necessary for an erection. Interestingly, cigarette smoking, in addition to causing generalized arterial blockage, may also cause the cavernous smooth muscle to lose its ability to dilate. Alteration of the neuro receptors in the smooth muscle may give an adverse response and, in effect, impair relaxation of the smooth muscle in response to the usual nitric oxide stimulation. On the other hand, if the trabecular smooth muscle and the vascular spaces of the penis are unable to relax sufficiently, the resulting sinusoidal expansion will be inadequate and the subtunical veins will not be compressed enough to maintain an erection. In Peyronie's disease, non-elastic scar tissue forms, primarily along the surface of the tunica albuginea, resulting in inadequate compression of the veins below the tunical surface, therefore preventing entrapment of the arterial blood in the normal fashion. Looking specifically at Parkinson's disease, most physicians, myself included, have been unaware of the high incidence of erectile dysfunction in this group of patients. Pathologic processes in certain regions of the brain, such as Parkinson's disease, stroke, Alzheimer's disease, brain tumors, and trauma can all result in erectile dysfunction. In diabetics, the effect on the nerve supply to the penis is thought to have more to do With erectile dysfunction than the diabetes-related effects of occlusive arterial disease. This collection of symptoms is referred to as a peripheral neuropathy. In addition to experiencing decreased function of the nerves leading to the penis, diabetics may exhibit effects on the nerves to the lower extremities and complain of numbness or tingling in their feet. Diabetic patients often have peripheral nerve damage that involves various parts of the body.