The site and type of brachial plexus injury determine the prognosis. Avulsion and rupture injuries require timely surgical intervention for any chance of recovery. For milder injuries involving buildup of scar tissue and for neurapraxia, the potential for improvement varies, but there is a fair prognosis for spontaneous recovery, with a 90–100% return of function.

Brachial plexus injury is found in both children and adults, but there is a difference between children and adults with BPI.

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.

Workers in certain fields are at risk of repetitive strains. Most occupational injuries are musculoskeletal disorders, and many of these are caused by cumulative trauma rather than a single event. Miners and poultry workers, for example, must make repeated motions which can cause tendon, muscular, and skeletal injuries.

Anatomically, damage to the axillary nerve or suppression of it causes the palsy. This suppression, referred to as entrapment, causes the nerve pathway to become smaller and impulses cannot move through the nerve as easily. Furthermore, if trauma causes damage to the myelin sheath, or injures the nerve another way, this will also reduce the ability of nerve impulse flow.

Usually, an outside force is acting to suppress the nerve, or cause nerve damage. Most commonly, shoulder dislocation or fractions in the shoulder can cause the palsy. Contact sports such as football and hockey can cause the injury Other cases have been caused by repeated crutch pressure or injuries accidentally caused by health professionals (iatrogenesis). Furthermore, following an anterior shoulder operation; damage to the axillary nerve is possible and has been documented by various surgeons, thus causing axillary nerve palsy. Other possible causes include: deep infection, pressure from a cast or splint, fracture of the humerus, or nerve disorders in which the nerves become inflamed.

There are rare causes of axillary nerve palsy that do occur. For instance, axillary nerve palsy can occur after there is blunt trauma in the shoulder area without any sort of dislocation or fracture. Examples of this blunt trauma may include: being hit by heavy an object, falling on shoulder, a strong blow while participating in boxing, or motor vehicle accidents. Another rare cause of axillary nerve palsy can occur after utilizing a side birthing position. When the patient lies on their side for a strenuous amount of time, they can develop axillary nerve palsy. This rare complication of labor can occur due to the prolonged pressure on the axillary nerve while in a side-birth position. Some patients who are diagnosed with nodular fasciitis may develop axillary nerve palsy if the location of the rapid growth is near the axilla. In the case of Nodular Fasciitis, a fibrous band or the growth of a schwannoma can both press against the nerve, causing axillary nerve palsy.

An injury to the axillary nerve normally occurs from a direct impact of some sort to the outer arm, though it can result from injuring a shoulder via dislocation or compression of the nerve. The axillary nerve comes from the posterior cord of the brachial plexus at the coracoid process and provides the motor function to the deltoid and teres minor muscles. An EMG can be useful in determining if there is an injury to the axillary nerve. The largest numbers of axillary nerve palsies arise due to stretch injuries which are caused by blunt trauma or iatrogenesis. Axillary nerve palsy is characterized by the lack of shoulder abduction greater than 30 degrees with or without the loss of sense in the low two thirds of the shoulder. Normally the patients that have axillary nerve palsy are involved in blunt trauma and have a number of shoulder injuries. Surgery is not always required to solve the problem (information from: Midha, Rajiv, Zager, Eric. Surgery of Peripheral Nerves: A Case-Based Approach. Thieme Medical Publishers, Inc. 2008.)

A stinger is an injury that is caused by restriction of the nerve supply to the upper extremity via the brachial plexus. The brachial plexus is formed by the anterior rami of the nerves at the 5th cervical level of the spinal cord all the way to the nerves at the 1st thoracic level of the spinal cord. The brachial plexus innervates the upper extremity as well as some muscles in the neck and shoulder. Damage to the brachial plexus can occur when the nerves are stretched too far from the head and neck; specifically the upper trunk of the plexus –nerve roots at the 5th and 6th cervical level –are primarily affected. The upper trunk provides part of the nerve to supply to the upper extremity via the Musculocutaneous, Axillary, Radial and Median nerves. It is for this reason that stingers do not affect both arms simultaneously, however it is possible for both arms to accrue injuries. Repeated nerve trauma can cause recurring stingers, chronic pain, and muscle weakness, while recovery can take weeks to months in severe cases.

There are many causes of TOS. The most frequent cause is trauma, either sudden (as in a clavicle fracture caused by a car accident), or repetitive (as in a legal secretary who works with his/her hands, wrists, and arms at a fast paced desk station with non-ergonomic posture for many years). TOS is also found in certain occupations involving lots of lifting of the arms and repetitive use of the wrists and arms.

One cause of arterial compression is trauma, and a recent case involving fracture of the clavicle has been reported.

The two groups of people most likely to develop TOS are those suffering from neck injuries due to traffic accidents and those who use computers in non-ergonomic postures for extended periods of time. TOS is frequently a repetitive stress injury (RSI) caused by certain types of work environments. Other groups which may develop TOS are athletes who frequently raise their arms above the head (such as swimmers, volleyball players, dancers, badminton players, baseball pitchers, and weightlifters), rock climbers, electricians who work long hours with their hands above their heads, and some musicians.

Among the causes of ulnar neuropathy are the following-

Much more commonly, ulnar neuropathy is caused by overuse of the triceps muscle and repetitive stress combined with poor ergonomics. Overused and hypertonic triceps muscle causes inflammation in the tendon and adhesions with the connective tissue surrounding that tendon and muscle. These in turn impinge on or trap the ulnar nerve. Ulnar neuropathy resulting from repetitive stress is amenable to massage and can usually be fully reversed without cortisone or surgery.

Center for Occupational and Environmental Neurology , Baltimore, MD has this to say:

“Repetitive Strain Injuries (RSI) refers to many different diagnoses of the neck/shoulder, arm, and wrist/hand area usually associated with work-related ergonomic stressors. Other terms used for Repetitive Strain Injuries are overuse syndrome, musculoskeletal disorders, and cumulative trauma disorders. Some of the more common conditions under these headings include:

Cubital Tunnel Syndrome-compression of the ulnar nerve in the cubital tunnel at the elbow.”

Axillary nerve palsy is a neurological condition in which the axillary (also called circumflex) nerve has been damaged by shoulder dislocation. It can cause weak deltoid and sensory loss below the shoulder. Since this is a problem with just one nerve, it is a type of Peripheral neuropathy called mononeuropathy. Of all brachial plexus injuries, axillary nerve palsy represents only .3% to 6% of them.

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.

Ulnar nerve entrapment is classified by location of entrapment. The ulnar nerve passes through several small spaces as it courses through the medial side of the upper extremity, and at these points the nerve is vulnerable to compression or entrapment—a so-called "pinched nerve". The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of ulnar nerve entrapment is at the elbow, followed by the wrist.

Causes or structures which have been reported to cause ulnar nerve entrapment include:

- Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, compression by anterior scalene muscles

- Problems originating in the chest: compression by pectoralis minor muscles

- Brachial plexus abnormalities

- Elbow: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers

- Forearm: tight flexor carpi ulnaris muscles

- Wrist: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome

- Artery aneurysms or thrombosis

- "Other": Infections, tumors, diabetes, hypothyroidism, rheumatism, and alcoholism

People vary in their tendency to get MSDs. Gender is a factor with a higher rate in women than men. Obesity is also a factor, with overweight individuals having a higher risk of some MSDs, specifically lower back.

After an anterior shoulder dislocation, the risk of a future dislocation is about 20%. This risk is greater in males than females.

Most people relieved of their carpal tunnel symptoms with conservative or surgical management find minimal residual or "nerve damage". Long-term chronic carpal tunnel syndrome (typically seen in the elderly) can result in permanent "nerve damage", i.e. irreversible numbness, muscle wasting, and weakness. Those that undergo a carpal tunnel release are nearly twice as likely as those not having surgery to develop trigger thumb in the months following the procedure.

While outcomes are generally good, certain factors can contribute to poorer results that have little to do with nerves, anatomy, or surgery type. One study showed that mental status parameters or alcohol use yields much poorer overall results of treatment.

Recurrence of carpal tunnel syndrome after successful surgery is rare.

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.

Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital phalanx of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the median nerve is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the thenar muscles. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.

In medicine, a stinger, also called a "burner" or "nerve pinch injury", is a neurological injury suffered by athletes, mostly in high-contact sports such as ice hockey, rugby, American football, and wrestling. The spine injury is characterized by a shooting or stinging pain that travels down one arm, followed by numbness and weakness. Many athletes in contact sports have suffered stingers, but they are often unreported to medical professionals.

Anyone who experiences significant trauma to his or her head or neck needs immediate medical evaluation for the possibility of a spinal injury. In fact, it's safest to assume that trauma victims have a spinal injury until proven otherwise because:

- The time between injury and treatment can be critical in determining the extent of complications and the amount of recovery

- A serious spinal injury is not always immediately obvious. If it is not recognized, more severe injury may occur

- Numbness or paralysis may develop immediately or come on gradually as bleeding or swelling occurs in or around the spinal cord

Repetitive strain injury (RSI) and associative trauma orders are umbrella terms used to refer to several discrete conditions that can be associated with repetitive tasks, forceful exertions, vibrations, mechanical compression, or sustained/awkward positions. Examples of conditions that may sometimes be attributed to such causes include edema, tendinosis (or less often tendinitis), carpal tunnel syndrome, cubital tunnel syndrome, De Quervain syndrome, thoracic outlet syndrome, intersection syndrome, golfer's elbow (medial epicondylitis), tennis elbow (lateral epicondylitis), trigger finger (so-called stenosing tenosynovitis), radial tunnel syndrome, ulnar tunnel syndrome, and focal dystonia.

Since the 1970s there has been a worldwide increase in RSIs of the arms, hands, neck, and shoulder attributed to the widespread use of typewriters/computers in the workplace that require long periods of repetitive motions in a fixed posture.

There is a growing consensus that psychosocial factors are another cause of some MSDs. Some theories for this causal relationship found by many researchers include increased muscle tension, increased blood and fluid pressure, reduction of growth functions, pain sensitivity reduction, pupil dilation, body remaining at heightened state of sensitivity. Although research findings are inconsistent at this stage, some of the workplace stressors found to be associated with MSDs in the workplace include high job demands, low social support, and overall job strain. Researchers have consistently identified causal relationships between job dissatisfaction and MSDs. For example, improving job satisfaction can reduce 17-69 per cent of work-related back disorders and improving job control can reduce 37-84 per cent of work-related wrist disorders.

There are many ways to acquire radial nerve palsy.

The term "Saturday Night Palsy" refers to an injury to the radial nerve in the spiral groove of the humerus caused while sleeping in a position that would under normal circumstances cause discomfort. It can occur when a person falls asleep while heavily medicated and/or under the influence of alcohol with the underside of the arm compressed by a bar edge, bench, chair back, or like object. Sleeping with the head resting on the arm can also cause radial nerve palsy.

Breaking the humerus and deep puncture wounds can also cause the condition.

Posterior interosseus palsy is distinguished from radial nerve palsy by the preservation of elbow extension.

Symptoms vary depending on the severity and location of the trauma; however, common symptoms include wrist drop (the inability to extend the wrist upward when the hand is palm down); numbness of the back of the hand and wrist, specifically over the first web space which is innervated by the radial nerve; and inability to voluntarily straighten the fingers or extend the thumb, which is performed by muscles of the extensor group, all of which are primarily innervated by the radial nerve. Loss of wrist extension is due to paralysis of the posterior compartment of forearm muscles; although the elbow extensors are also innervated by the radial nerve, their innervation is usually spared because the compression occurs below, distal, to the level of the axillary nerve, which innervates the long head of the triceps, and the upper branches of the radial nerve that innervate the remainder of the Triceps.

Erb's palsy or Erb–Duchenne palsy is a paralysis of the arm caused by injury to the upper group of the arm's main nerves, specifically the severing of the upper trunk C5–C6 nerves. These form part of the brachial plexus, comprising the ventral rami of spinal nerves C5–C8 and thoracic nerve T1. These injuries arise most commonly, but not exclusively, from shoulder dystocia during a difficult birth. Depending on the nature of the damage, the paralysis can either resolve on its own over a period of months, necessitate rehabilitative therapy, or require surgery.

Median nerve palsy is often caused by deep, penetrating injuries to the arm, forearm, or wrist. It may also occur from blunt force trauma or neuropathy.

Median nerve palsy can be separated into 2 subsections—high and low median nerve palsy. High MNP involves lesions at the elbow and forearm areas. Low median nerve palsy results from lesions at the wrist. Compression at the different levels of the median nerve produce variable symptoms and/or syndromes. The areas are:

- Underneath Struthers' ligament

- Passing by the bicipital aponeurosis (also known as lacertus fibrosus)

- Between the two heads of the pronator teres

- Compression in the carpal tunnel causes carpal tunnel syndrome

In tennis players, about 39.7% have reported current or previous problems with their elbow. Less than one quarter (24%) of these athletes under the age of 50 reported that the tennis elbow symptoms were "severe" and "disabling," while 42% were over the age of 50. More women (36%) than men (24%) considered their symptoms severe and disabling. Tennis elbow is more prevalent in individuals over 40, where there is about a four-fold increase among men and two-fold increase among women. Tennis elbow equally affects both sexes and, although men have a marginally higher overall prevalence rate as compared to women, this is not consistent within each age group, nor is it a statistically significant difference.

Playing time is a significant factor in tennis elbow occurrence, with increased incidence with increased playing time being greatery for respondents under 40. Individuals over 40 who played over two hours doubled their chance of injury. Those under 40 increased it 3.5 fold compared to those who played less than two hours per day.

Radial nerve dysfunction is also known as radial neuropathy or radial mononeuropathy. It is a problem associated with the radial nerve resulting from injury consisting of acute trauma to the radial nerve. The damage has sensory consequences, as it interferes with the radial nerve's innervation of the skin of the posterior forearm, lateral three digits, and the dorsal surface of the side of the palm. The damage also has motor consequences, as it interferes with the radial nerve's innervation of the muscles associated with the extension at the elbow, wrist, and figers, as well the supination of the forearm. This type of injury can be difficult to localize, but relatively common, as many ordinary occurrences can lead to the injury and resulting mononeuropathy. One out of every ten patients suffering from radial nerve dysfunction do so because of a fractured humerus.

Radial Tunnel Syndrome is caused by increased pressure on the radial nerve as it travels from the upper arm (the brachial plexus) to the hand and wrist.