There are two common systems used to classify or describe different kinds of brachial plexus injuries. The simplest uses the severity of the injury from least to greatest: (1) stretch, (2) rupture and (3) avulsion. The other uses the location of the injury.
This injury refers to a simple stretching of the nerve fibers in the brachial plexus—the major bundle of nerves that starts at the base of the neck and runs through the shoulder and down into the arm and hand. The bundle consists of trunks (primary nerves…think tree) and cords (smaller and thinner…think branches). The stretch occurs in the trunks or cords themselves, or in the area where the primary nerves divide to form the cords. The severity of a stretch injury depends upon the degree of stretch and the disruption of the tissue stretched. A stretch injury with the sheath of the nerve intact can result in a “neurapraxia,” a short-term injury, which can have symptoms such as decreased movement or sensation. As the swelling inside the nerve goes down, nerve functions return. Stretch injuries are generally most likely to result in a full recovery. Where there is no clinically significant damage to nerve tissue, they usually heal within a few weeks or months. Often, it is only time passing that will tell us if this is just a stretch injury (healing and the nerves function again) or something more serious.
This is the most serious type of injury. Picture a tree in your mind, standing tall, the deep buried roots carrying nutrients and sustaining life. Now picture the tree ripped out of the ground by a tornado, and the churned up earth in and around the hole where the roots had been. The “hole” that is left when the nerve root is torn out of the spinal cord can impair the flow of the nerve impulses that are supposed to be going up and down the spinal cord without disruption. But the disruption in nerve flow from an avulsion injury can cause a reduced ability to move the leg that is on the same side as the injury, and even a reduction in the growth of the leg. The only known cause of avulsion injuries is extreme traction (pulling) applied to the brachial plexus.
This injury refers to one or more nerves being stretched beyond their limits to the point where they actually tear, in whole or in part. The severity of the symptoms related to a partial rupture depends upon the extent of the damage and whether or not the nerve is so badly damaged that it will be difficult for the nerve to heal or repair itself. If the nerve sheath (covering of the nerve) is intact, then the chances of healing are better, but if the nerve fibers or nerve sheath are disrupted, the chances are reduced.
After a partial rupture, the nerves attempt to grow back together. This often results in the formation of a neuroma, which is a ball made up of scar tissue and nerve fibers that are growing in an attempt to reconnect the disrupted nerve supply. An EMG may be necessary to help determine if there has been or is likely to be meaningful “reconnection” of the nerve impulses that used to flow through the injured portion of the brachial plexus.
A complete rupture is when the nerve is torn apart and there are no connecting nerve fibers. The body will still attempt to heal a complete rupture with nerve regeneration and formation of scar tissue, also resulting in a neuroma. But it is unlikely the body can provide meaningful repair from a complete rupture.
Surgery is sometimes necessary to repair a complete or partial rupture.
The location of a brachial plexus injury determines what functions are impaired or lost.
An Erb’s Palsy (also known as Erb-Duchenne Palsy) refers to injuries to the fibers that originate at the fifth , sixth and sometimes the seventh cervical nerve roots, in the upper part of the plexus. There is considerable variation in how an injury at this level will manifest itself, but generally C5, C6 and C7 affect the shoulder area, upper arm, the chest wall, and the thumb, index and middle fingers of the hand.
Klumpke Palsy refers to an injury involving the lower part of the brachial plexus. Damage to the eighth cervical nerve root and the first thoracic nerve root can severely impair movement of the wrist and hand.
A pan injury or total injury involves some amount of damage to both the upper and lower parts of the brachial plexus.
Horner Syndrome (also called Bernard-Horner syndrome and oculosympathetic palsy) generally refers to a drooping eyelid on the side affected by the brachial plexus injury. Other indications are a slight elevation of the lower lid, constricted pupil, a perceptible lag when the eye dilates. Sometimes there will be an impression that the eye is sunk in, or decreased sweating on the affected side of the face. A child with this condition may sometimes wind up with different colored eyes, because the unequal nerve stimulation interferes with the body’s process for coloring a growing child’s eyes.
This illustration provides an example of some of the physical effects of an Erb’s Palsy injury, as well as an example of the Horner Syndrome.