Brachial plexus injury

Brachial plexus injury
Classification and external resources
Specialty
ICD-10	G54.0, P14.3, S14.3
ICD-9-CM	353.0, 767.6, 953.4
DiseasesDB	31267
MedlinePlus	001418
Patient UK	Brachial plexus injury
MeSH	D020516

The brachial plexus is a network of nerves that conducts signals from the spinal cord, which is housed in the spinal canal of the vertebral column (or spine), to the shoulder, arm and hand. These nerves originate in the fifth, sixth, seventh and eighth cervical (C5–C8), and first thoracic (T1) spinal nerves, and innervate the muscles and skin of the chest, shoulder, arm and hand. Brachial plexus injuries, or lesions, are caused by damage to those nerves.

Brachial plexus injuries, or lesions, can occur as a result of shoulder trauma, tumours, or inflammation. The rare Parsonage-Turner Syndrome causes brachial plexus inflammation without obvious injury, but with nevertheless disabling symptoms. But in general, brachial plexus lesions can be classified as either traumatic or obstetric. Obstetric injuries may occur from mechanical injury involving shoulder dystocia during difficult childbirth. Traumatic injury may arise from several causes. "The brachial plexus may be injured by falls from a height on to the side of the head and shoulder, whereby the nerves of the plexus are violently stretched....The brachial plexus may also be injured by direct violence or gunshot wounds, by violent traction on the arm, or by efforts at reducing a dislocation of the shoulder joint".

Signs and symptoms

Signs and symptoms may include a limp or paralyzed arm, lack of muscle control in the arm, hand, or wrist, and lack of feeling or sensation in the arm or hand. Although several mechanisms account for brachial plexus injuries, the most common is nerve compression or stretch. Infants, in particular, may suffer brachial plexus injuries during delivery and these present with typical patterns of weakness, depending on which portion of the brachial plexus is involved. The most severe form of injury is nerve root avulsion, which results in complete weakness in corresponding muscles. This usually accompanies high-velocity impacts that occurs during motor vehicle or bicycle accidents.

Disabilities

Based on the location of the nerve damage, brachial plexus injuries can affect part of or the entire arm. For example, musculocutaneous nerve damage weakens elbow flexors, median nerve damage causes proximal forearm pain, and paralysis of the ulnar nerve causes weak grip and finger numbness. In some cases, these injuries can cause total and irreversible paralysis. In less severe cases, these injuries limit use of these limbs and cause pain.

The cardinal signs of brachial plexus injury then, are weakness in the arm, diminished reflexes, and corresponding sensory deficits.

1. Erb's palsy. "The position of the limb, under such conditions, is characteristic: the arm hangs by the side and is rotated medially; the forearm is extended and pronated. The arm cannot be raised from the side; all power of flexion of the elbow is lost, as is also supination of the forearm".
2. In Klumpke's paralysis, a form of paralysis involving the muscles of the forearm and hand, a characteristic sign is the clawed hand, due to loss of function of the ulnar nerve and the intrinsic muscles of the hand it supplies.

Causes

In most cases the nerve roots are stretched or torn from their origin, since the meningeal covering of a nerve root is thinner than the sheath enclosing the nerve. The epineurium of the nerve is contiguous with the dura mater, providing extra support to the nerve.

Brachial plexus lesions typically result from excessive stretching; from rupture injury where the nerve is torn but not at the spinal cord; or from avulsion injuries, where the nerve is torn from its attachment at the spinal cord. A build-up of scar tissue around a brachial plexus injury site can also put pressure on the injured nerve, disrupting innervation of the muscles. Although injuries can occur at any time, many brachial plexus injuries happen during birth: the baby's shoulders may become impacted during the birth process causing the brachial plexus nerves to stretch or tear. Obstetric injuries may occur from mechanical injury involving shoulder dystocia during difficult childbirth, the most common of which result from injurious stretching of the child's brachial plexus during birth, mostly vaginal, but occasionally Caesarean section. The excessive stretch results in incomplete sensory and/or motor function of the injured nerve.

Injuries to the brachial plexus result from excessive stretching or tearing of the C5-T1 nerve fibers. These injuries can be located in front of or behind the clavicle, nerve disruptions, or root avulsions from the spinal cord. These injuries are diagnosed based on clinical exams, axon reflex testing, and electrophysiological testing. Brachial plexus injuries require quick treatment in order for the patient to make a full functional recovery (Tung, 2003). These types of injuries are most common in young adult males.

Traumatic brachial plexus injuries may arise from several causes, including sports, high-velocity motor vehicle accidents, especially in motorcyclists, but also all-terrain-vehicle (ATV) accidents. Injury from a direct blow to the lateral side of the scapula is also possible. The severity of nerve injuries may vary from a mild stretch to the nerve root tearing away from the spinal cord (avulsion). "The brachial plexus may be injured by falls from a height on to the side of the head and shoulder, whereby the nerves of the plexus are violently stretched… The brachial plexus may also be injured by direct violence or gunshot wounds, by violent traction on the arm, or by efforts at reducing a dislocation of the shoulder joint".

Brachial plexus lesions can be divided into three types:

1. An upper brachial plexus lesion, which occurs from excessive lateral neck flexion away from the shoulder. Most commonly, forceps delivery or falling on the neck at an angle causes upper plexus lesions leading to Erb's palsy. This type of injury produces a very characteristic sign called Waiter's tip deformity due to loss of the lateral rotators of the shoulder, arm flexors, and hand extensor muscles.
2. Less frequently, the whole brachial plexus lesion occurs;
3. most infrequently, sudden upward pulling on an abducted arm (as when someone breaks a fall by grasping a tree branch) produces a lower brachial plexus lesion, in which the eighth cervical (C8) and first thoracic (T1) nerves are injured "either before or after they have joined to form the lower trunk. The subsequent paralysis affects, principally, the intrinsic muscles of the hand and the flexors of the wrist and fingers". This results in a form of paralysis known as Klumpke's paralysis.

Mechanism

Injury to the brachial plexus can happen in numerous environments. These may include contact sports, motor vehicle accidents and birth. Although these are but a common few events, there is one of two mechanisms of injury that remain constant during the point of injury. The two mechanisms that can occur are traction and heavy impact. These two methods disturb the nerves of the brachial plexus and cause the injury.

Traction, also known as stretch injury, is one of the mechanisms that cause brachial plexus injury. The nerves of the brachial plexus are damaged due to the forced pull by the widening of the shoulder and neck. This is a closer look at the traction mechanism at the cervical spine. The arrowed red line represents the stretch of the nerves. Depending on the force, lesions may occur.

Anatomy

This image shows the anterior view of the 5 brachial plexus nerves on the human arm.
Axillary,Median,Musculocutaneous,Radial,Ulnar.

The brachial plexus is made up of spinal nerves that are part of the peripheral nervous system. It includes sensory and motor nerves that innervate the upper limbs. The brachial plexus includes the last 4 cervical nerves (C5-C8) and the 1st thoracic nerve (T1). Each of those nerves splits into smaller trunks, divisions, and cords. The lateral cord includes the musculocutaneous nerve and lateral branch of the median nerve. The medial cord includes the medial branch of the median nerve and the ulnar nerve. The posterior cord includes the axillary nerve and radial nerve.

Traction

Traction occurs from severe movement and causes a pull or tension among the nerves. There are two types of traction: downward traction and upward traction. In downward traction there is tension of the arm which forces the angle of the neck and shoulder to become broader. This tension is forced and can cause lesions of the upper roots and trunk of the nerves of the brachial plexus. Upward traction also results in the broadening of the neck and shoulder angle but this time the nerves of T1 and C8 are torn away.

Impact

Heavy impact to the shoulder is the second common mechanism to causing injury to the brachial plexus. Depending on the severity of the impact, lesions can occur at all nerves in the brachial plexus. The location of impact also affects the severity of the injury and depending on the location the nerves of the brachial plexus may be ruptured or avulsed. Some forms of impact that affect the injury to the brachial plexus are shoulder dislocation, clavicle fractures, hyperextension of the arm and sometimes delivery at birth. During the delivery of a baby, the shoulder of the baby may graze against the pelvic bone of the mother. During this process, the brachial plexus can receive damage resulting in injury. The incidence of this happening at birth is 1 in 1000. This is very low compared to the other identified brachial plexus injuries.

Classification

The severity of brachial plexus injury is determined by the type of nerve damage. There are several different classification systems for grading the severity of nerve and brachial plexus injuries. Most systems attempt to correlate the degree of injury with symptoms, pathology and prognosis. Seddon's classification, devised in 1943, continues to be used, and is based on three main types of nerve fiber injury, and whether there is continuity of the nerve.

1. Neurapraxia: The mildest form of nerve injury. It involves an interruption of the nerve conduction without loss of continuity of the axon. Recovery takes place without wallerian degeneration.
2. Axonotmesis: Involves axonal degeneration, with loss of the relative continuity of the axon and its covering of myelin, but preservation of the connective tissue framework of the nerve (the encapsulating tissue, the epineurium and perineurium, are preserved).
3. Neurotmesis: The most severe form of nerve injury, in which the nerve is completely disrupted by contusion, traction or laceration. Not only the axon, but the encapsulating connective tissue lose their continuity. The most extreme degree of neurotmesis is transsection, although most neurotmetic injuries do not produce gross loss of continuity of the nerve but rather, internal disruption of the nerve architecture sufficient to involve perineurium and endoneurium as well as axons and their covering. It requires surgery, with unpredictable recovery.

A more recent and commonly used system described by the late Sir Sydney Sunderland, divides nerve injuries into five degrees: first degree or neurapraxia, following on from Seddon, in which the insulation around the nerve called myelin is damaged but the nerve itself is spared, and second through fifth degree, which denotes increasing severity of injury. With fifth degree injuries, the nerve is completely divided.

Diagnosis

The diagnosis may be confirmed by an EMG examination in 5 to 7 days. The evidence of denervation will be evident. If there is no nerve conduction 72 hours after the injury, then avulsion is most likely.. The most advanced diagnostic method is MR imaging of the brachial plexus using a high Tesla MRI scanner like 1.5 T or more. MR helps aid in the assessment of the injuries in specific context of site, extent and the nerve roots involved. In addition, assessment of the cervical cord and post traumatic changes in soft tissues may also be visualised.

Treatment

Treatment for brachial plexus injuries includes orthosis/splinting, occupational or physical therapy and, in some cases, surgery. Some brachial plexus injuries may heal without treatment. Many infants improve or recover within 6 months, but those that do not have a very poor outlook and will need further surgery to try to compensate for the nerve deficits. The ability to bend the elbow (biceps function) by the third month of life is considered an indicator of probable recovery, with additional upward movement of the wrist, as well as straightening of thumb and fingers an even stronger indicator of excellent spontaneous improvement. Gentle range of motion exercises performed by parents, accompanied by repeated examinations by a physician, may be all that is necessary for patients with strong indicators of recovery.

Rehabilitation

There are many treatments to facilitate the process of recovery in people who have brachial plexus injuries. Improvements occur slowly and the rehabilitation process can take up to many years. Many factors should be considered when estimating recovery time, such as initial diagnosis of the injury, severity of the injury, and type of treatments used. Some forms of treatment include nerve grafts, medication, surgical decompression, nerve transfer, physical therapy, and occupational therapy.

Physical therapy

Having an effective occupational and physical therapy program is important when dealing with the unfortunate circumstances of brachial plexus injuries. One of the main goals of rehabilitation is to prevent muscle atrophy until the nerves regain function. Electrical stimulation is an effective treatment to help patients reach this fundamental goal. Exercises that involve shoulder extension, flexion, elevation, depression, abduction and adduction facilitate healing by engaging the nerves in the damaged sites as well as improve muscle function. Stretching is done on a daily basis to improve or maintain range of motion. Stretching is important in order to rehabilitate since it increases the blood flow to the injury as well as facilitates nerves in functioning properly.

Epidemiology

Adults

BPI Traumatic event

The epidemiology of brachial plexus injury also known as BPI is found in both children and adults, but there is a difference between children and adults with BPI. The occurrence of adult brachial plexus injuries in the 1900s multiple traumatic injuries for North America population is with a prevalence of about 1.2%. BPI is most commonly found with young healthy adults, from ages 14 to 63 years old, along with 50% of patients between the ages of 19 and 34 years old, and with male patients being 89% at risk Brachial plexus injury is a traumatic event and that has been shown to increase over the years.

Children

Incidence of OBPP

As for the epidemiology of brachial plexus injury in children OBPP also known, as obstetrical brachial plexus palsy occurred the most for young children ranging from 0.38 to 1.56 per 1000 live births due to the type of care and the average birth weight of infants in different regions of the world. For example a study was done for the incidence of OBPP where USA is about 1.51 cases per 1000 live births, a Canadian study, where the incidence was between 0.5 and 3 injuries per 1000 live Birth, and European countries, such as a Dutch study reported an incidence of 4.6 per 1000 births. Newborns with brachial plexus injury was most commonly found in Diabetic women whose babies weighed more than 4.5 kg at birth along with different types of deliveries. Brachial plexus injury risks for newborns are increased with gained birth weight, birth delivery where a vacuum is assisted, and not being able to handle glucose.

Traumatic injuries

Motorcycles and BPI

BPI has shown to occur 44% through 70% with traumatic injuries, such as motorcycle accidents, sporting activities, or even at the work places. With 22% being motorcycle injuries and about 4.2% having plexus damage. People that have accidents with riding motorcycles and snowmobiles, have higher risks of getting BPI.

Treatment

The exercises mentioned above can be done to help rehabilitate from mild cases of the injury. However, in more serious brachial plexus injuries surgical interventions can be used. Function can be restored by nerve repairs, nerve replacements, and surgery to remove tumors causing the injury. Another crucial factor to note is that psychological problems can hinder the rehabilitation process due to a lack of motivation from the patient. On top of promoting a lifetime process of physical healing, it is important to not overlook the psychological well-being of a patient. This is due to the possibility of depression or complications with head injuries.

Prognosis

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 build-up 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.

External links

• Brachial plexus injury with illustrations
• Types of Brachial Plexus Injury at GetHow
• lesson3brachialplexus at The Anatomy Lesson by Wesley Norman (Georgetown University)

See also

• Backpack palsy