This syndrome is predominantly found in young women, but also occurs in children, teenagers and octogenarians.

Anterior cutaneous nerve entrapment syndrome (ACNES) is a nerve entrapment condition that causes chronic pain of the abdominal wall. It occurs when nerve endings of the lower thoracic intercostal nerves (7–12) are 'entrapped' in abdominal muscles, causing a severe localized nerve (neuropathic) pain that is usually experienced at the front of the abdomen.

ACNES syndrome is frequently overlooked and unrecognized, although the incidence is estimated to be 1:2000 patients.

The relative unfamiliarity with this condition often leads to significant diagnostic delays and misdiagnoses, often resulting in unnecessary diagnostic interventions and futile procedures. Physicians often misdiagnose ACNES as irritable bowel syndrome or "functional disorders", as symptoms of the condition are not dispositive.

People with diabetes mellitus are at higher risk for any kind of peripheral neuropathy, including ulnar nerve entrapments.

Cubital tunnel syndrome is more common in people who spend long periods of time with their elbows bent, such as when holding a telephone to the head. Flexing the elbow while the arm is pressed against a hard surface, such as leaning against the edge of a table, is a significant risk factor. The use of vibrating tools at work or other causes of repetitive activities increase the risk, including throwing a baseball.

Damage to or deformity of the elbow joint increases the risk of cubital tunnel syndrome. Additionally, people who have other nerve entrapments elsewhere in the arm and shoulder are at higher risk for ulnar nerve entrapment. There is some evidence that soft tissue compression of the nerve pathway in the shoulder by a bra strap over many years can cause symptoms of ulnar neuropathy, especially in very large-breasted women.

Most patients diagnosed with cubital tunnel syndrome have advanced disease (atrophy, static numbness, weakness) that might reflect permanent nerve damage that will not recover after surgery. When diagnosed prior to atrophy, weakness or static numbness, the disease can be arrested with treatment. Mild and intermittent symptoms often resolve spontaneously.

Anterior interosseous syndrome or Kiloh-Nevin syndrome I is a medical condition in which damage to the anterior interosseous nerve (AIN), a motor branch of the median nerve, causes pain in the forearm and a characteristic weakness of the pincer movement of the thumb and index finger.

Most cases of AIN syndrome are due to a transient neuritis, although compression of the AIN can happen. Trauma to the median nerve have also been reported as a cause of AIN syndrome.

Although there is still controversy among upper extremity surgeons, AIN syndrome is now regarded as a neuritis (inflammation of the nerve) in most cases; this is similar to Parsonage–Turner syndrome. Although the exact etiology is unknown, there is evidence that it is caused by an immune mediated response.

Studies are limited, and no randomized controlled trials have been performed regarding the treatment of AIN syndrome. While the natural history of AIN syndrome is not fully understood, studies following patients who have been treated without surgery show that symptoms can resolve starting as late as one year after onset. Other retrospective studies have shown that there is no difference in outcome in surgically versus nonsurgically treated patients. Surgical decompression is rarely indicated in AIN syndrome. Indications for considering surgery include a known space-occupying lesion that is compressing the nerve (a mass) and persistent symptoms beyond 1 year of conservative treatment.

The lateral femoral cutaneous nerve most often becomes injured by entrapment or compression where it passes between the upper front hip bone (ilium) and the inguinal ligament near the attachment at the anterior superior iliac spine (the upper point of the hip bone). Less commonly, the nerve may be entrapped by other anatomical or abnormal structures, or damaged by diabetic or other neuropathy or trauma such as from seat belt injury in an accident.

The nerve may become painful over a period of time as weight gain makes underwear, belting or the waistband of pants gradually exert higher levels of pressure. Pain may be acute and radiate into the rib cage, and into the groin, thigh, and knee. Alternately, weight loss or aging may remove protective fat layers under the skin, so the nerve can compress against underwear, outer clothing, and—most commonly— by belting. Long periods of standing or leg exercise that increases tension on the inguinal ligament may also cause pressure.

In terms of the prognosis of ulnar neuropathy early decompression of the nerve sees a return to normal ability (function). which should be immediate.Severe cubital tunnel syndrome tends to have a faster recovery process in individuals below the age of 70, as opposed to those above such an age. Finally, revisional surgery for cubital tunnel syndrome does not result well for those individuals over 50 years of age.

The entire distribution of the nerve is rarely affected. Usually, the unpleasant sensation(s) affect only part of the skin supplied by the nerve.

Injuries of the forearm with compression of the nerve is the most common cause: examples include

supracondylar fractures, often associated with haemorrhage into the deep musculature;

injury secondary to open reduction of a forearm fracture; or dislocation of the elbow.⁠⁠

Direct trauma from a penetrating injury such as a stab wound is a common cause for the syndrome.

Fibrous bands or arcuate (curved) ligaments may entrap the median as well as the anterior interosseous nerves, in which case a patient may experience numbness as well as pain.⁠⁠

Rheumatoid disease and gouty arthritis may be a predisposing factor in anterior interosseous nerve entrapment.

Very similar syndromes can be caused by more proximal lesions, such as brachial plexus neuritis.⁠

Anterior interosseous nerve entrapment or compression injury remains a difficult clinical diagnosis because it is mainly a motor nerve and the syndrome is often mistaken for finger ligamentous injury.⁠

The exact incidence of Frey syndrome is unknown. The disorder most often occurs as a complication of the surgical removal of a parotid gland (parotidectomy). The percentage of individuals who develop Frey syndrome after a parotidectomy is controversial and reported estimates range from 30-50 percent. In follow-up examinations, approximately 15 percent of affected individuals rated their symptoms as severe. Frey syndrome affects males and females in equal numbers.

The international debate regarding the relationship between CTS and repetitive motion in work is ongoing. The Occupational Safety and Health Administration (OSHA) has adopted rules and regulations regarding cumulative trauma disorders. Occupational risk factors of repetitive tasks, force, posture, and vibration have been cited.

The relationship between work and CTS is controversial; in many locations, workers diagnosed with carpal tunnel syndrome are entitled to time off and compensation.

Some speculate that carpal tunnel syndrome is provoked by repetitive movement and manipulating activities and that the exposure can be cumulative. It has also been stated that symptoms are commonly exacerbated by forceful and repetitive use of the hand and wrists in industrial occupations, but it is unclear as to whether this refers to pain (which may not be due to carpal tunnel syndrome) or the more typical numbness symptoms.

A review of available scientific data by the National Institute for Occupational Safety and Health (NIOSH) indicated that job tasks that involve highly repetitive manual acts or specific wrist postures were associated with incidents of CTS, but causation was not established, and the distinction from work-related arm pains that are not carpal tunnel syndrome was not clear. It has been proposed that repetitive use of the arm can affect the biomechanics of the upper limb or cause damage to tissues. It has also been proposed that postural and spinal assessment along with ergonomic assessments should be included in the overall determination of the condition. Addressing these factors has been found to improve comfort in some studies. A 2010 survey by NIOSH showed that 2/3 of the 5 million carpal tunnel cases in the US that year were related to work. Women have more work-related carpal tunnel syndrome than men.

Speculation that CTS is work-related is based on claims such as CTS being found mostly in the working adult population, though evidence is lacking for this. For instance, in one recent representative series of a consecutive experience, most patients were older and not working. Based on the claimed increased incidence in the workplace, arm use is implicated, but the weight of evidence suggests that this is an inherent, genetic, slowly but inevitably progressive idiopathic peripheral mononeuropathy.

Decompression surgery is a "last resort", according to surgeons who perform the operation. The surgery is performed by a small number of surgeons in a limited number of countries. The validity of decompression surgery as a treatment and the existence of entrapment as a cause of pelvic pain are highly controversial. While a few doctors will prescribe decompression surgery, most will not. Notably, in February 2003 the European Association of Urology in its "Guidelines on Pelvic Pain" said that expert centers in Europe have found no cases of PNE and that surgical success is rare:

Three types of surgery have been done to decompress the pudendal nerve: transperineal, transgluteal, and transichiorectal. A follow-up of patients of this surgery after 4 years found that 50% felt their pain had improved to various extents, although control patients were not followed up for comparison. If surgery does bring relief of symptoms, patients will mostly experience it within 4 weeks of surgery.

However, the studies and surgical methods cited above generally focused on the Alcock’s canal and the area between the sacrotuberous and sacrospinous ligaments as likely sites for entrapment. More recent studies have identified possible entrapment sites anterior to Alcock’s canal.

A nerve may be compressed by prolonged or repeated external force, such as sitting with one's arm over the back of a chair (radial nerve), frequently resting one's elbows on a table (ulnar nerve), or an ill-fitting cast or brace on the leg (peroneal nerve). Part of the patient's body can cause the compression and the term "entrapment neuropathy" is used particularly in this situation. The offending structure may be a well-defined lesion such as a tumour (for example a lipoma, neurofibroma or metastasis), a ganglion cyst or a haematoma. Alternatively, there may be expansion of the tissues around a nerve in a space where there is little room for this to occur, as is often the case in carpal tunnel syndrome. This may be due to weight gain or peripheral oedema (especially in pregnancy), or to a specific condition such as acromegaly, hypothyroidism or scleroderma and psoriasis.

Some conditions cause nerves to be particularly susceptible to compression. These include diabetes, in which the blood supply to the nerves is already compromised, rendering the nerve more sensitive to minor degrees of compression. The genetic condition HNPP is a much rarer cause.

Anything compromising the tunnel of the posterior tibial nerve proves significant in the risk of causing TTS. Neuropathy can occur in the lower limb through many modalities, some of which include obesity and inflammation around the joints. By association, this includes risk factors such as RA, compressed shoes, pregnancy, diabetes and thyroid diseases

In regards to the pathophysiology of ulnar neuropathy:the axon, and myelin can be affected. Within the axon, fascicles to individual muscles could be involved, with subsequent motor unit loss and amplitude decrease. Conduction block means impaired transmission via a part of the nerve. Conduction block can mean myelin damage to the involved area, slowing of conduction or significant spreading out of the temporal profile of the response with axonal integrity is a hallmark of demyelination.

There are stretches and exercises which have provided reduced levels of pain for some people. There are different sources of pain for people since there are so many ligament, muscles and nerves in the area. Sometimes women do pelvic floor exercises for compression after childbirth. However, there have been cases where the wrong stretches make the constant pain worse. Some people need to strengthen the muscles, others should stretch, while for some people it is purely neurological. There have been cases where doing stretches have helped bicyclists. Acupuncture has helped decrease pain levels for some people, but is generally ineffective. Chiropractic adjustments to the lower back have also helped some patients with pudendal nerve issues.

A variety of patient factors can lead to CTS, including heredity, size of the carpal tunnel, associated local and systematic diseases, and certain habits. Non-traumatic causes generally happen over a period of time, and are not triggered by one certain event. Many of these factors are manifestations of physiologic aging.

Examples include:

- Rheumatoid arthritis and other diseases that cause inflammation of the flexor tendons.

- With hypothyroidism, generalized myxedema causes deposition of mucopolysaccharides within both the perineurium of the median nerve, as well as the tendons passing through the carpal tunnel.

- During pregnancy women experience CTS due to hormonal changes (high progesterone levels) and water retention (which swells the synovium), which are common during pregnancy.

- Previous injuries including fractures of the wrist.

- Medical disorders that lead to fluid retention or are associated with inflammation such as: inflammatory arthritis, Colles' fracture, amyloidosis, hypothyroidism, diabetes mellitus, acromegaly, and use of corticosteroids and estrogens.

- Carpal tunnel syndrome is also associated with repetitive activities of the hand and wrist, in particular with a combination of forceful and repetitive activities

- Acromegaly causes excessive secretion of growth hormones. This causes the soft tissues and bones around the carpel tunnel to grow and compress the median nerve.

- Tumors (usually benign), such as a ganglion or a lipoma, can protrude into the carpal tunnel, reducing the amount of space. This is exceedingly rare (less than 1%).

- Obesity also increases the risk of CTS: individuals classified as obese (BMI > 29) are 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS.

- "Double-crush syndrome" is a debated hypothesis that compression or irritation of nerve branches contributing to the median nerve in the neck, or anywhere above the wrist, increases sensitivity of the nerve to compression in the wrist. There is little evidence, however, that this syndrome really exists.

- Heterozygous mutations in the gene SH3TC2, associated with Charcot-Marie-Tooth, confer susceptibility to neuropathy, including the carpal tunnel syndrome.

It is difficult to determine the exact cause of Tarsal Tunnel Syndrome. It is important to attempt to determine the source of the problem. Treatment and the potential outcome of the treatment may depend on the cause. Anything that creates pressure in the Tarsal Tunnel can cause TTS. This would include benign tumors or cysts, bone spurs, inflammation of the tendon sheath, nerve ganglions, or swelling from a broken or sprained ankle. Varicose veins (that may or may not be visible) can also cause compression of the nerve. TTS is more common in athletes and other active people. These people put more stress on the tarsal tunnel area. Flat feet may cause an increase in pressure in the tunnel region and this can cause nerve compression. Those with lower back problems may have symptoms. Back problems with the L4, L5 and S1 regions are suspect and might suggest a "Double Crush" issue: one "crush" (nerve pinch or entrapment) in the lower back, and the second in the tunnel area. In some cases, TTS can simply be idiopathic.

Rheumatoid Arthritis has also been associated with TTS.

Nerve compression syndrome or compression neuropathy, also known as entrapment neuropathy, is a medical condition caused by direct pressure on a nerve. It is known colloquially as a "trapped nerve", though this may also refer to nerve root compression (by a herniated disc, for example). Its symptoms include pain, tingling, numbness and muscle weakness. The symptoms affect just one particular part of the body, depending on which nerve is affected. Nerve conduction studies help to confirm the diagnosis. In some cases, surgery may help to relieve the pressure on the nerve but this does not always relieve all the symptoms. Nerve injury by a single episode of physical trauma is in one sense a compression neuropathy but is not usually included under this heading.

Other causes may include:

- Anticonvulsant pharmaceutical drugs, such as topiramate, sultiame, and acetazolamide

- Anxiety and/or panic disorder

- Benzodiazepine withdrawal syndrome

- Beta alanine

- Carpal tunnel syndrome

- Cerebral amyloid angiopathy

- Chiari malformation

- Coeliac disease (celiac disease)

- Complex regional pain syndrome

- Decompression sickness

- Dehydration

- Dextromethorphan (recreational use)

- Fabry disease

- Erythromelalgia

- Fibromyalgia

- Fluoroquinolone toxicity

- Guillain–Barré syndrome (GBS)

- Heavy metals

- Herpes zoster

- Hydroxy alpha sanshool, a component of Sichuan peppers

- Hyperglycemia (high blood sugar)

- Hyperkalemia

- Hyperventilation

- Hypoglycemia (low blood sugar)

- Hypocalcemia, and in turn:

- Hypermagnesemia, a condition in which hypocalcemia itself is typically observed as a secondary symptom

- Hypomagnesemia, often as a result of long term proton-pump inhibitor use

- Hypothyroidism

- Immunodeficiency, such as chronic inflammatory demyelinating polyneuropathy (CIDP)

- Intravenous administering of strong pharmaceutical drugs acting on the central nervous system (CNS), mainly opioids, opiates, narcotics; especially in non-medical use (drug abuse)

- Ketorolac

- Lidocaine poisoning

- Lomotil

- Lupus erythematosus

- Lyme disease

- Menopause

- Mercury poisoning

- Migraines

- Multiple sclerosis

- Nitrous oxide, long-term exposure

- Obdormition

- Pyrethrum and pyrethroid (pesticide)

- Rabies

- Radiation poisoning

- Sarcoidosis

- Scorpion stings

- Spinal disc herniation or injury

- Spinal stenosis

- Stinging nettles

- Syringomyelia

- Transverse myelitis

- Vitamin B deficiency

- Vitamin B deficiency

- Withdrawal from certain selective serotonin reuptake inhibitors (or serotonin-specific reuptake inhibitors) (SSRIs), such as paroxetine or serotonin-norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine

Frey's syndrome often results as a side effect of surgeries of or near the parotid gland or due to injury to the auriculotemporal nerve, which passes through the parotid gland in the early part of its course. The Auriculotemporal branch of the Trigeminal nerve carries parasympathetic fibers to the sweat glands of the scalp and the parotid salivary gland. As a result of severance and inappropriate regeneration, the parasympathetic nerve fibers may switch course, resulting in "gustatory Sweating" or sweating in the anticipation of eating, instead of the normal salivatory response.

It is often seen with patients who have undergone endoscopic thoracic sympathectomy, a surgical procedure wherein part of the sympathetic trunk is cut or clamped to treat sweating of the hands or blushing. The subsequent regeneration or nerve sprouting leads to abnormal sweating and salivating. It can also include discharge from the nose when smelling certain food.

Rarely, Frey's syndrome can result from causes other than surgery, including accidental trauma, local infections, sympathetic dysfunction and pathologic lesions within the parotid gland.

An example of such, rare trauma or localized infection; can be seen in situations where a hair follicle has become ingrown and is causing trauma or localized infection near or over one of the branches of the auriculotemporal nerve.

Not much research has been done on the epidemiology of congenital trigger thumbs. There are a few reports on the incidence in their respective studies. The most recent data comes from a Japanese study by Kukichi and Ogino where they found an incidence 3.3 trigger thumbs per 1,000 live births in 1 year old children.

Initial line of treatment is with anti-inflammatory drugs or cortisone injections. There have been trials with gloves which help protect the ulnar nerve from compression. The most radical treatment option is surgery to relieve tension in the volar carpal ligament which forms the roof of Guyon's canal, thereby reducing compression on the ulnar nerve.

The place of chiropractic-, physical-, occupational-, massage- and osteopathic therapy was not confirmed in scientific studies. These treatments can be both expensive as well as dangerous (causing permanent damage when performed wrongly).

It is advised to consult a physician beforehand starting any therapy, albeit an alternative approach, to avoid any permanent nerve damage.

Ulnar tunnel syndrome may be characterized by the location or zone within the Guyon's canal at which the ulnar nerve is compressed. The nerve divides into a superficial sensory branch and a deeper motor branch in this area. Thus, Guyon's canal can be separated into three zones based on which portion of the ulnar nerve are involved. The resulting syndrome results in either muscle weakness or impaired sensation in the ulnar distribution.

Zone 2 type syndromes are most common, while Zone 3 are least common.

A retrospective postal survey of 396 men found that 4% had significant genital pain for more than one year that required surgical intervention.

Another study contacted 470 vasectomy patients and received 182 responses, finding that 18.7% of respondents experienced chronic genital pain with 2.2% of respondents experiencing pain that adversely affected quality of life.

The most robust study of post-vasectomy pain, according to the American Urology Association's Vasectomy Guidelines 2012 (amended 2015) found a rate of 14.7% reported new-onset scrotal pain at 7 months after vasectomy with 0.9% describing the pain as "quite severe and noticeably affecting their quality of life".