The primary nerve fibers to the penis are from the dorsal nerve of the penis, a branch of the pudendal nerve. The cavernosal nerves are a part of the autonomic nervous system and incorporate both sympathetic and parasympathetic fibers. They travel posterolaterally along the prostate and enter the corpora cavernosa and corpus spongiosum to regulate blood flow during erection and detumescence. The dorsal somatic nerves are also branches of the pudendal nerves. They are primarily responsible for penile sensation. 
Garlic is considered to help effectively in dealing with the impotence and ED problems because it has high levels of allicin which can help to improve blood flow and blood circulation. A small research of Dr. Graham Jackson, consultant cardiologist at Guys and St Thomas’ NHS Trust discovered that consuming 4 cloves of garlic every day for 3 months can help much in improving the erection in 6 out of 7 volunteers struggling with impotence.
Patients at high cardiovascular risk should not be treated for ED until their cardiac condition is stabilize. These conditions include unstable or refractory angina, myocardial infarction or cerebrovascular accident within the past 2 weeks, uncontrolled hypertension, New York Heart Association (NYHA) Functional Classification III-IV congestive heart failure, high-risk arrhythmias, hypertrophic obstructive cardiomyopathies, and moderate-to-severe valvular disease.25 This class of drugs is also contraindicated in patients who use nitroglycerin or nitrate-containing compounds.26, 27
Chancellor et al. (109) compared VEDs with papaverine injections in 18 males with SCI. The injections and pumps were equally effective in inducing erections and no adverse effects from the treatments were reported. Treatment arms were crossed over, subsequently seven men chose the VED and seven men chose the papavarine highlighting equal efficacy in this population. In another treatment arm topical minoxidil was applied without any effective erections achieved by the study subjects.
MSA is a neurodegenerative disease of undetermined etiology, where ED is an early prominent sign occurring in 40% of men at the time of diagnosis (46,47). ED occurs in the majority of patients and the exact cause of it is unknown (48). Like PD, MSA likely affects the dopaminergic pathways within the brain essential for arousal (49). Orthostatic hypotension (OH) as a causal factor has been refuted by evidence that sildenafil can overcome reduced filling pressures, and the ED usually precedes the development of OH (46,49,50). Similar to other neurologic disorders that lead to ED, other disease related factors such as psychosocial stress, the burden of chronic illness, changed appearance, fatigue, decreased fine motor movement of fingers, immobility and diminished self-esteem due to loss of independence may contribute as well (51).
Also called vacuum devices, penile pumps are devices that are placed over the penis to draw blood into the shaft. Once the vacuum creates an erection, the retaining band is slid down to the lower end of the penis and the pump is removed. An erection typically will last long enough for intercourse but your penis may be cold to the touch and the rubber band may restrict ejaculation.22
A physical cause can be identified in about 80% of cases. These include cardiovascular disease, diabetes mellitus, neurological problems such as following prostatectomy, hypogonadism, and drug side effects. Psychological impotence is where erection or penetration fails due to thoughts or feelings; this is somewhat less frequent, in the order of about 10% of cases. In psychological impotence, there is a strong response to placebo treatment.
Lifestyle choices that impair blood circulation can contribute to ED. Smoking, excessive drinking, and drug abuse may damage the blood vessels and reduce blood flow to the penis. Smoking makes men with atherosclerosis particularly vulnerable to ED. Being overweight and getting too little exercise also contribute to ED. Studies indicate that men who exercise regularly have a lower risk of ED.
Like all diabetic complications, ED can occur even when you have followed your doctor’s advice and carefully managed your diabetes. Also like all diabetes complications, ED is less likely to occur with good blood sugar control. Poorly controlled diabetes and high cholesterol increase the chances of vascular complications, which may lead to ED or other circulatory problems. In addition, regular smoking and alcohol use can contribute to ED.
PDE5i for ED in patients with MS can be considered as reasonably effective and safe. Fowler et al. performed a randomized, multicenter, double-blind, flexible dose trial with open label extensions comparing sildenafil to placebo (75). A nearly 4-fold increase in effective erections was noted in the treatment arm, 96% vs. 24%. Sexual satisfaction and overall satisfaction were also improved in the treatment group based on IIEF scores, and quality of life assessments. Lombardi et al. evaluated tadalafil use in men with MS (71). Seventy eight percent of the men responded with improved erections, better quality of life with regards to sexual function, partner relationship and family life. Just less than half the men who responded to the tadalafil did so at the lower dosage of 10 mg. Subjects in either studies did not have any significant adverse side effects beyond flushing, and headache with PDE5i use.
ICI therapy often produces a reliable erection, which comes down after 20-30 minutes or with climax. Since the ICI erection is not regulated by your penile nerves, you should not be surprised if the erection lasts after orgasm. The most common side effect of ICI therapy is a prolonged erection. Prolonged erections (>1 hour) can be reversed by a second injection (antidote) in the office.