Brachial Plexus Injuries Health Article

Definition

Brachial plexus injuries affect the nerves that originate from the spinal cord behind the head and neck (cervical nerves).

Description

The brachial plexus are nerves that leave the cervical vertebrae (but originate in the brain) and extend to peripheral structures (muscles/organs) to transmit motor and sensory nerve impulses. The brachial plexus consists of several cervical nerve roots, which include: C4, sending fibers to the shoulder and trapezius muscle; C5, sending fibers to the deltoid muscle and sides of upper arm or distal radius and involved with shoulders abduction; C6, involved with elbow flexion and fibers in the biceps and lateral forearm and thumb; C7, fibers to the triceps muscle, index and middle finger tips and involved with elbow extension; and C8, involved with extension of thumb and 4th and 5th fingers. Injury to the brachial plexus can involve avulsion injuries (nerve torn from attachment to the spinal cord), which are the most serious type of injury; neuroma injuries, due to injury causing scar formation tissue, which compresses nerves; rupture injuries, nerve is torn, but not at the spinal cord; and stretch injuries, nerve is damaged, but not torn.

Sports related injuries to the the cervical spine are common, especially injury to cervical vertebra 5 (C5) and C6. Erb described this condition with paralysis in 1874. Other names for the disorder include "burner" or "stinger" syndrome and cervical nerve pinch syndrome. Traumatic sports injury to the brachial plexus is characterized by a classical symptom—burning sensation that radiates down an upper extremity. The sensation may be short lived (2 minutes) or in chronic cases may last as long as two weeks. There are three common mechanisms that cause BPI, which include: direct impact to Erb point resulting in brachial plexus compression; traction caused by lateral flexion opposite from affected side; and nerve compression caused by hyperextension of the neck.

Obstetrical brachial plexus paralysis (OBPP) refers to injury to all or part of the brachial plexus during delivery. The condition was first described by Smellie in 1764 who described bilateral (both arms) paralysis in the newborn. Klumpke described paralysis (of the lower plexus) in 1885. Erb described paralysis of the upper brachial plexus (upper C5-C6 nerve damage) in 1874. Lower brachial plexus injuries are called Klumpke palsies and upper brachial plexus injury are termed Erb palsies. Injury is rare but is more prevalent in neonates born by cesarean delivery.

Demographics

In the United States a true measurement of new and existing cases is undetermined largely due to the significant underreporting of injuries. Approximately 5% of all peripheral nerve injuries results from trauma to the brachial plexus. Research studies conducted on college football players reported approximately 45% to 65% experience BPI during their collegiate careers. Additionally, it is estimated that there is an 87% recurrence rate. Estimates in other countries are not possible due to significant underreporting.

The incidence (number of new cases) of OBPP ranges from 0.2–4% of live births globally. The World Health Organization estimates the worldwide incidence is approximately 1–2%. In the United States it is rare and the incidence is 0.2% of live births. Every year 1–2 babies per 1000 live births are affected by obstetrical brachial nerve injury.

Causes and symptoms

BPI typically occurs as a result of a blow to the head, shoulder, and/or Erb point in an athlete during a contact sport. There are two grades of BPI. Grade 1 occurs when there is an interruption of nerve function due to demyelination. Muscle weakness is often detected soon after injury. Grade 2 describes more extensive damage to deeper and vital nerve areas (axons). Muscle weakness is often present and if persistent could mean a higher-grade lesion. Further tests for grade 2 BPI are indicated to fully assess the extent of nerve degeneration.

The causes of OBPP include shoulder dystocia, large birth weight, and breech delivery (vertex presentation accounts for 94–97% of cases). Maternal diabetes (mother has diabetes) is associated as a risk factor. Mothers who have had several children who were recorded to be large babies have an increased risk for delivering neonates with OBPP.

Commonly, affected athletes complain and describe burning and/or numbness in the neck, shoulder, or upper extremity (affected arm). Symptoms typically occur after a blow to the head or shoulder. These symptoms include burning sensation in the neck, pain in the neck, (also called dysesthesias), and a feeling of weakness or "heaviness" in the affected arm. Bilateral (on both arms) numbness possibly indicates a more severe form of cervical cord injury. Symptoms can last from a few seconds to weeks.

Infants affected by OBPI may present with flail arms at birth. The affected arm may be internally rotated and pronated and devoid of elbow and shoulder movement (Erb palsy). If brachial plexus paralysis is present the entire hand and arm is flail with no movement ability.

The symptoms of OBPP can be grouped according to Sunderland's classification, which was proposed in 1951. A first-degree injury (also called neuropraxia or "stretch injuries") involves nerve injury that can completely resolve within 12 weeks. A second-degree injury results in severe trauma and nerve compression, but essential nerve elements are still intact and complete recovery is expected. A third-degree nerve injury is more severe, and essential nerve structures have been damaged as well as possible muscle damage. Some nerves and muscles may be permanently damaged. A fourth-degree injury results from extensive nerve damage that affects muscles, and typically it requires corrective surgical repair. The most severe form of obstetrical brachial plexus injury is fifth-degree injury, which is complete transaction of the nerve (the nerve is completely cut).