If nocturnal erections do not occur, the impotence is most likely physical. Additional testing is then required to identify the precise cause of the problem. Physical impotence occurs when there is a problem with any of the systems needed to get or maintain an erection. The good news is that potency can usually be restored when a man is treated for underlying medical conditions, when medications are adjusted or when lifestyle habits are changed. Hardening of the arteries can affect the artery leading to the penis so that it cannot dilate enough to deliver all the blood necessary for an erection.
Impotence can also occur if the nerves that control blood flow to the penis are damaged.
Impotence may result if nerves or blood vessels that control the flow of blood to the penis are affected. In some cases, keeping the diet and blood sugar under control can decrease impotence. But permanent nerve damage can result in a chronic problem. Disease of the Nervous System. Some conditions, such as multiple sclerosis, Parkinson's disease and spinal cord injuries, can affect or cause impotence.