Erectile function is a very integrated process. Numerous nerves, blood vessels, hormones, and other chemical messengers are responsible for getting and maintaining an erection.
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Erectile function is controlled by a branch of the nervous system called the autonomic nervous system.¹ Within this system, the sympathetic nervous system inhibits erections, and the parasympathetic nervous system facilitates erections. However, ejaculation is facilitated by the sympathetic nervous system.
There are three types of erections that you may experience.
Psychogenic erections occur in response to afferent sensory stimulation (T11-L2 and S2-S4 nerves) to trigger central dopaminergic erection from the preoptic area.
A psychogenic erection occurs through fantasies or after receiving auditory, mental, emotional, or visual stimulation.
The nerves that are important for a psychogenic erection are:
Nerves that travel from the brain through the spinal cord (T11-L2 and S2-S4)
Pelvic splanchnic nerves
(Reflexogenic erections, which often remain present in men with spinal cord injury above the sacral level, occur following genital stimulation and are mediated in the spinal cord and autonomic nuclei)
A reflexogenic erection occurs when physical contact with the penis or a surrounding erotic area occurs.
The important nerves for a reflexogenic erection are:
the pudendal nerve
the dorsal penile nerve
pelvic splanchnic nerves
Occurs during Rapid Eye Movement (REM) sleep. Nocturnal erections that occur during REM sleep likely result from suppression of inhibitory sympathetic outflow by the pontine reticular formation and amygdala.
The nerves that control psychogenic erectile function first include descending pathways from the brain. The brain sends messages down the spinal cord to activate a specific area called the sacral erection center, located near the bottom of the spinal cord.
From here, the signals are transmitted¹ through the pelvic splanchnic nerve to a collection of nerve fibers called the pelvic plexus. Then, signals travel through the cavernous nerve, which activates the erectile tissue of the penis.
Reflexogenic erections do not involve psychological stimulation. They rely on tactile stimuli to the genitals. Therefore, these erections are controlled by the nerves in the lowest part of the spinal cord, where the parasympathetic pathway arises.²
The process of a reflexogenic erection originates at sensory receptors located in and around the penile skin. When these receptors are activated, messages regarding sensory information like touch are sent via the dorsal and pudendal nerves to the sacral erection center in the spinal cord.
Subsequently, some³ of these messages are transmitted to the brain, while some are sent via the cavernous nerve to induce the erection.
The cavernous nerves are important for both psychogenic and reflexogenic erections.
The pelvic splanchnic nerves lead to the cavernous nerves. These nerves help initiate erections using a neurotransmitter (a type of chemical messenger) called acetylcholine. Although acetylcholine isn’t directly responsible for generating erections, it helps to modulate them by facilitating the release of the neurotransmitter Nitric Oxide (NO), which does produce erections.
The cavernous nerves, which activate the erection, use a neurotransmitter called nitric oxide. This transmitter is essential for erection because it enables the penis to fill with blood.
The nerve impulses enter the erection chambers of the penis, known as the corpora cavernosa. Stimulation ultimately causes the smooth muscles in the corpora cavernosa to relax and the arteries to widen, so that blood can flow in.
Neuropathy, disease, or dysfunction of peripheral nerves can increase someone’s chance of developing erectile dysfunction (ED).⁴
ED is a condition that describes the frequent inability to achieve or maintain an erection firm enough for satisfactory sexual performance.
Although several factors can cause ED or increase the risk of getting it, it’s thought that around 5%⁵ of all causes are nerve-related (neurogenic).
Some ways that nerve-related ED can occur are:
Neurological conditions damage the nerves and can cause ED. These could include:
Multiple sclerosis (MS)
Pudendal neuralgia⁶ is a disease where the pudendal nerve is damaged and/or irritated, causing pelvic pain. Research suggests pudendal neuralgia is a cause of ED, but in this case, it’s usually reversible.
Pudendal neuralgia can be caused by physical trauma to the pelvic region or more insidious causes such as cycling, childbirth, constipation, or iatrogenically during pelvic surgery.
Surgery to the prostate or the pelvis can also damage the pudendal nerve. One study noted that more than 80% of patients who have this type of surgery develop cavernous nerve injury erectile dysfunction (CNIED). CNIED was also shown to be responsible for over 14% of ED cases.
Spinal cord injuries affect reflexogenic and psychogenic erections differently, depending on where the injury occurs on the spinal cord.
Reflexogenic erections: Most men with spinal cord injuries continue to experience reflex erections if the injury occurs at higher levels on the spine. However, if the sacral segments (the lower parts of the spinal cord) are injured, reflexogenic erections may stop.
Psychogenic erections: If the spinal cord injury is at a low level, psychogenic erections often still occur. If the injury is higher up, men may not be able to easily have psychogenic erections. Likewise, they may not be able to get these erections with a complete spinal cord injury, which removes all feeling and the ability to control movement, below the level of injury.
Currently, little evidence exists to show which treatments are best for ED caused by nerve damage. Your doctor may thus consider traditional treatments. If a nerve is trapped or compressed, this may be preferential to surgery.
If you think you may have ED, it’s recommended that you see your doctor as soon as possible. A medical professional can help determine what’s causing your ED and decide on the best course of action for treating it and helping you regain erectile function, where possible.
Management of neurogenic ED mostly involves phosphodiesterase type 5 inhibitors (PDE5 inhibitors). These are viewed as the first-line treatment option for men with ED relating to spinal cord injuries and/or cavernous nerve damage. PDE5 inhibitors are also recommended in the American Urological Association Guideline on the Management of ED.
According to one study on the use of medications for nerve-related ED, PDE5 inhibitors:
improved erections in 85% of men with Parkinson’s disease
improved erections in 96% of men with multiple sclerosis.
Common PDE5 inhibitors include:
Injection therapy is also thought to be beneficial for ED caused by nerve damage.
Injection therapy involves directly injecting medication (such as alprostadil, papaverine, or phentolamine) into the side of your penis. This relaxes the blood vessels and allows more blood to flow into the penis.
It’s thought that penile injection therapy is particularly beneficial for nerve-related ED because it acts locally and can bypass neuronal pathways. However, this treatment is still considered second-line and would only be considered if PDE5 inhibitors fail.
According to experts, vacuum erection devices have successfully treated neurogenic-related ED.
The process involves placing the penis in a clear, plastic tube. The vacuum pump creates negative pressure, which helps the penis to become erect.
Research⁷ suggests that pudendal nerve decompression is a potential treatment for ED caused by problems relating to the pudendal nerve.
Currently, pudendal nerve decompression is the standard of care for ED caused by pudendal nerve entrapment. However, several studies point towards its potential use, noting that participants experienced improvements in ED and/or restoration of erectile function.
Lifestyle changes, if possible, can help improve nerve function and subsequently erectile function.
The European Association of Urology⁸ recommends that men with ED consider making certain lifestyle changes before beginning traditional ED treatment.
Some ways to make changes in your lifestyle include:
Anxiety and stress can inhibit erections because they activate the sympathetic nervous system. So, lifestyle changes that help to reduce stress and improve mental well-being may be beneficial.
Some research has gone into the role that diet plays in peripheral nerve health and function.
The evidence so far suggests that the following nutrients⁹ are associated with nerve protection and health. It may be a good idea to make sure you have enough in your diet.
Polyunsaturated fatty acids, including omega-3s
If you have diabetes, it’s advised to make lifestyle changes so you can control your diabetes as much as possible.
This is also important in the context of erections because type 2 diabetes can damage the nerves and contribute to the development of ED.
Other lifestyle changes that are promoted to help treat ED in general include:
Maintaining a healthy weight
Eating a Mediterranean-style diet
Doing 30 minutes of moderate-intensity aerobic exercise most days each week.
A review of studies¹⁰ suggests that men with ED have a lower quality of life than men without ED. They’re more likely to:
Have worse psychological, social, and physical well-being
Have less satisfaction in their sexual relationship
Experience anxiety and depression that may be related to difficulties in sexual performance.
ED is also thought to reduce the quality of life of the partner and the couple as a whole.
However, remember that treatment for ED is possible. Effective and safe ways to manage your ED to ensure you maintain a good quality of life are available.
Nerves play a vital role in the production and control of psychogenic and reflexogenic erections. Damage to one or more of these nerves, among other causes, can result in ED.
Regardless, it’s possible to manage and treat the condition so that you can enjoy a satisfactory sexual relationship and quality of life.
Sexual dysfunction due to pudendal neuralgia: A systematic review | Translation Andrology and Urology (2021)
Sexual dysfunction due to pudendal neuralgia: A systematic review | NIH: National Library of Medicine (2021)
Erectile dysfunction (2016)
Erectile dysfunction | Johns Hopkins Medicine
Erection of the penis: Anatomy and physiology | Urology Textbook