Differential considerations include similar rotator cuff denervation syndromes such as Parsonage–Turner syndrome, and compression of the suprascapular nerve at the spinoglenoid notch in which the infraspinatus, and to a lesser degree supraspinatus is involved.

Treatment is decompression of the quadrilateral space, with supportive therapy in recalcitrant cases.

Despite its wasting and at times long-lasting effects, most cases resolve themselves and recovery is usually good in 18–24 months, depending on how old the person in question is. For instance, a six-year-old could have brachial neuritis for only around 6 months, but a person in their early fifties could have it for over 3 years.

The differential focuses on distinguishing it from similar entities such as quadrilateral space syndrome, which involves the teres minor and variably the deltoid, and suprascapular nerve impingement at the spinoglenoid notch, which predominantly involves the infraspinatus.

"Infant’s persistent thumb-clutched hand, flexion-adduction deformity of the thumb, pollex varus, thumb in the hand deformity."

Congenital clasped thumb describes an anomaly which is characterized by a fixed thumb into the palm at the metacarpophalangeal joint in one or both hands.

The incidence and genetic background are unknown. A study of Weckesser et al. showed that boys are twice as often affected with congenital clasped thumb compared to girls. The anomaly is in most cases bilateral (present in both hands).

A congenital clasped thumb can be an isolated anomaly, but can also be attributed to several syndromes.

Injury of axillary nerve (axillary neuropathy) is a condition that can be associated with a surgical neck of the humerus fracture.

It can also be associated with a dislocated shoulder or with traction injury to the nerve, which may be caused by over-aggressive stretching or blunt trauma that does not result in fracture or dislocation. One form of this injury is referred to as axillary nerve palsy.

Injury most commonly occurs proximal to the quadrilateral space.

Injury in this nerve causes paralysis (as always) to the muscles innervated by it, most importantly deltoid muscle. This muscle is the main abductor of the shoulder joint from 18 to 90 degrees (from 0 to 18 by supraspinatus). Injury can result in a reduction in shoulder abduction. So a test can be applied to a patient with injury of axillary nerve by trying to abduct the injured shoulder against resistance.

The pain from axillary neuropathy is usually dull and aching rather than sharp, and increases with increasing range of motion. Many people notice only mild pain but considerable weakness when they try to use the affected shoulder.

A compartment space is anatomically determined by an unyielding fascial (and osseous) enclosure of the muscles. The anterior compartment syndrome of the lower leg (often referred to simply as anterior compartment syndrome), can affect any and all four muscles of that compartment: tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius.

This term is often mistakenly used to describe various related/proximal conditions, including Anterior Shin Splints. It is important to distinguish between the two, as shin splints rarely causes serious health problems, while Anterior Compartment Syndrome can lead to irreversible damage.

The true compartment syndrome arises due to increased pressure within the unyielding anterior compartment of the leg. The pressure obstructs venous outflow, which causes further swelling and increased pressure. The resultant ischemia leads to necrosis (death of tissue) of the muscles and nerves. The process can begin with swelling of the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and/or the peroneus tertius muscles in response to strong eccentric contractions sufficient to produce postexercise soreness.

A compartment syndrome is an increased pressure within a muscular compartment that compromises the circulation to the muscles.

Shoulder impingement syndrome, also called subacromial impingement, painful arc syndrome, supraspinatus syndrome, swimmer's shoulder, and thrower's shoulder, is a clinical syndrome which occurs when the tendons of the rotator cuff muscles become irritated and inflamed as they pass through the subacromial space, the passage beneath the acromion. This can result in pain, weakness and loss of movement at the shoulder.

The most common symptoms in impingement syndrome are pain, weakness and a loss of movement at the affected shoulder. The pain is often worsened by shoulder overhead movement and may occur at night, especially if the patient is lying on the affected shoulder. The onset of the pain may be acute if it is due to an injury or may be insidious if it is due to a gradual process such as an osteoarthritic spur. The pain has been described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.

The range of motion at the shoulder may be limited by pain. A painful arc of movement may be present during forward elevation of the arm from 60° to 120°. Passive movement at the shoulder will appear painful when a downwards force is applied at the acromion but the pain will ease once the downwards force is removed.

Radial dysplasia, also known as radial club hand or radial longitudinal deficiency, is a congenital difference occurring in a longitudinal direction resulting in radial deviation of the wrist and shortening of the forearm. It can occur in different ways, from a minor anomaly to complete absence of the radius, radial side of the carpal bones and thumb. Hypoplasia of the distal humerus may be present as well and can lead to stiffnes of the elbow. Radial deviation of the wrist is caused by lack of support to the carpus, radial deviation may be reinforced if forearm muscles are functioning poorly or have abnormal insertions. Although radial longitudinal deficiency is often bilateral, the extent of involvement is most often asymmetric.

The incidence is between 1:30,000 and 1:100,000 and it is more often a sporadic mutation rather than an inherited condition. In case of an inherited condition, several syndromes are known for an association with radial dysplasia, such as the cardiovascular Holt-Oram syndrome, the gastrointestinal VATER syndrome and the hematologic Fanconi anemia and TAR syndrome. Other possible causes are an injury to the apical ectodermal ridge during upper limb development, intrauterine compression, or maternal drug use (thalidomide).

Diagnosing the congenital clasped thumb is difficult in the first three to four months of life, as it is normal when the thumb is clutched into the palm in these first months.

Diagnoses that cause the same flexion or adduction abnormalities of the thumb are:

- Congenital clasped thumb

- Congenital Trigger thumb (flexion of the interphalangeal joint) - Trigger finger

- Spasticity: overstimulation of muscles

Syndrome associated flexion-adduction of the thumb:

- Freeman-Sheldon syndrome (a congenital, heritable affection of the face, the hands, the feet and some joints)

- Distal arthrogryposis

- MASA syndrome

- X-linked hydrocephalus

- Adducted thumb syndrome

- Waardenburg syndrome

- Whistling face syndrome (Freeman-Sheldon syndrome)

- Digitotalar dysmorphism

- Multiple pterygium syndrome

Up to a quarter of all severe ligament or capsular knee injuries leading to a haemarthrosis are associated with cartilage damage that can lead to progressive degenerative arthritis.

Classification of radial dysplasia is practised through different models. Some only include the different deformities or absences of the radius, where others also include anomalies of the thumb and carpal bones. The Bayne and Klug classification discriminates four different types of radial dysplasia. A fifth type was added by Goldfarb et al. describing a radial dysplasia with participation of the humerus. In this classification only anomalies of the radius and the humerus are taken in consideration. James and colleagues expanded this classification by including deficiencies of the carpal bones with a normal distal radius length as type 0 and isolated thumb anomalies as type N.

Type N: Isolated thumb anomaly

Type 0: Deficiency of the carpal bones

Type I: Short distal radius

Type II: Hypoplastic radius in miniature

Type III: Absent distal radius

Type IV: Complete absent radius

Type V: Complete absent radius and manifestations in the proximal humerus

The term absent radius can refer to the last 3 types.

Both sex are equally affected

Any age group can develop a parapheryngeal abscess but it is most commonly seen in children and adolescents. Adults who are immunocompromised are also at high risk.

RPA is usually caused by a bacterial infection originating from the nasopharynx, tonsils, sinuses, adenoids or middle ear. Any upper respiratory infection (URI) can be a cause. RPA can also result from a direct infection due to penetrating injury or a foreign body. RPA can also be linked to young children who do not have adequate dental care or brush their teeth properly.

Infection can occur from:

- Pharynx: acute and chronic infection of tonsil and adenoids

- Teeth: dental infection occurs from lower last molar tooth

- Ear: bezold abscess and petrositis

- Other space: infection of parotid retropharyngeal space

- External trauma: penetrating injuries of neck, injection of local anaesthetic

Thumb hypoplasia is a spectrum of congenital abnormalities of the thumb varying from small defects to absolute retardation of the thumb. It can be isolated, when only the thumb is affected, and in 60% of the cases it is associated with radial dysplasia (or radial club, radius dysplasia, longitudinal radial deficiency). Radial dysplasia is the condition in which the forearm bone and the soft tissues on the thumb side are underdeveloped or absent.

In an embryo the upper extremities develop from week four of the gestation. During the fifth to eighth week the thumb will further develop. In this period something goes wrong with the growth of the thumb but the exact cause of thumb hypoplasia is unknown.

One out of every 100,000 live births shows thumb hypoplasia. In more than 50% of the cases both hands are affected, otherwise mainly the right hand is affected.

About 86% of the children with hypoplastic thumb have associated abnormalities. Embryological hand development occurs simultaneously with growth and development of the cardiovascular, neurologic and hematopoietic systems. Thumb hypoplasia has been described in 30 syndromes wherein those abnormalities have been seen. A syndrome is a combination of three or more abnormalities. Examples of syndromes with an hypoplastic thumb are Holt-Oram syndrome, VACTERL association and thrombocytopenia absent radius (TAR syndrome).

While exercise is used to maintain muscle, bone and cardiac health during spaceflight, its effects on ICP and IOP have yet to be determined. The effects of resistive exercise on the development of ICP remains controversial. An early investigation showed that the brief intrathoractic pressure increase during a Valsalva maneuver resulted in an associated rise in ICP. Two other investigations using transcranial Doppler ultrasound techniques showed that resistive exercise without a Valsalva maneuver resulted in no change in peak systolic pressure or ICP. The effects of resistive exercise in IOP are less controversial. Several different studies have shown a significant increase in IOP during or immediately after resistive exercise.

There is much more information available regarding aerobic exercise and ICP. The only known study to examine ICP during aerobic exercise by invasive means showed that ICP decreased in patients with intracranial hypertension and those with normal ICP. They suggested that because aerobic exercise is generally done without Valsalva maneuvers, it is unlikely that ICP will increase during exercise. Other studies show global brain blood flow increases 20-30% during the transition from rest to moderate exercise.

More recent work has shown that an increase in exercise intensity up to 60% VOmax results in an increase in CBF, after which CBF decreases towards (and sometimes below) baseline values with increasing exercise intensity.

People with yellow nail syndrome have been found to have a moderately reduced lifespan compared to people without the condition.

It has been said by many dog owners that limber tail had been caused shortly (24 hours) after swimming in water that is too cold or on rare occasions too warm and indeed this has certainly produced this very condition. The actual cause is unknown but it may be caused by the narrowing of the space through which the spinal cord passes, typically due to degenerative change to the intervertebral disk spaces. These underlying changes may not lead to visible change until the problem is suddenly exacerbated, such as during physical activity, after trauma, etc. Occasionally other changes are seen prior to or in conjunction with limber tail disease, such as urinary or fecal incontinence, postural abnormalities in the pelvic limb, or pain in response to touching the lower back.

A link between increased ICP and altered sodium and water retention was suggested by a report in which 77% of IIH patients had evidence of peripheral edema and 80% with orthostatic retention of sodium and water. Impaired saline and water load excretions were noted in the upright position in IIH patients with orthostatic edema compared to lean and obese controls without IIH. However, the precise mechanisms linking orthostatic changes to IIH were not defined, and many IH patients do not have these sodium and water abnormalities. Astronauts are well known to have orthostatic intolerance upon reentry to gravity after long-duration spaceflight, and the dietary sodium on orbit is also known to be in excess of 5 grams per day in some cases. The Majority of the NASA cases did have high dietary sodium during their increment. The ISS program is working to decrease in-flight dietary sodium intake to less than 3 grams per day. Prepackaged foods for the International Space Station were originally high in sodium at 5300 mg/d. This amount has now been substantially reduced to 3000 mg/g as a result of NASA reformulation of over ninety foods as a conscious effort to reduce astronaut sodium intake.

Retropharyngeal abscess (RPA) is an abscess located in the tissues in the back of the throat behind the posterior pharyngeal wall (the retropharyngeal space). Because RPAs typically occur in deep tissue, they are difficult to diagnose by physical examination alone. RPA is a relatively uncommon illness, and therefore may not receive early diagnosis in children presenting with stiff neck, malaise, difficulty swallowing, or other symptoms listed below. Early diagnosis is key, while a delay in diagnosis and treatment may lead to death. Parapharyngeal space communicates with retropharyngeal space and an infection of retropharyngeal space can pass down behind the esophagus into the mediastinum. RPAs can also occur in adults of any age.

RPA can lead to airway obstruction or sepsis – both life-threatening emergencies. Fatalities normally occur from patients not receiving treatment immediately and suffocating prior to knowing that anything serious was wrong.

Hemarthrosis (or haemarthrosis) is a bleeding into joint spaces.

It is a common feature of Hemophilia.

Limber tail syndrome, or acute caudal myopathy, is a disorder of the muscles in the tail, usually affecting working dogs.

It is an injury occurring mostly in sporting or working dogs such as English Pointers, English Setters, Foxhounds, Beagles, and Labrador Retrievers. Limber tail syndrome is also known as swimmer's tail, cold water tail, broken tail, dead tail, "happy tail" or broken wag.