A brachial plexus injury is damage to the network of nerves that runs from your spinal cord through your neck and into your arm, controlling nearly all movement and sensation in your shoulder, arm, and hand. These injuries range from mild stretches that heal on their own to severe tears that can cause permanent paralysis. The brachial plexus is formed by nerve roots from the fifth cervical vertebra down to the first thoracic vertebra (C5 through T1), and the specific roots affected determine which parts of your arm lose function.
What the Brachial Plexus Controls
This nerve network is responsible for powering virtually every muscle in your upper limb and providing sensation from your shoulder to your fingertips. Different branches handle different jobs. The musculocutaneous nerve controls your biceps and the muscles that bend your elbow, plus sensation along the outer forearm. The median nerve powers most of the forearm flexors and thumb muscles, carrying sensation from your thumb, index finger, middle finger, and half of your ring finger. The ulnar nerve handles the small intrinsic muscles of the hand and provides feeling to your pinky and the other half of the ring finger.
Because these functions are divided among specific nerve roots, the location of an injury creates very predictable patterns of weakness and numbness. Damage to the upper roots (C5 and C6) affects the shoulder and elbow. Damage to the lower roots (C8 and T1) affects the hand. Injuries that involve all five roots can leave the entire arm without function.
Types of Brachial Plexus Injury
Brachial plexus injuries fall into three main categories based on severity.
Neuropraxia (stretch): The nerve is stretched but not torn. This is the mildest and most common form. It happens through either compression (such as the head rotating and pressing on a nerve root) or traction (the nerve being pulled downward or sideways). Neuropraxia typically resolves on its own as the nerve recovers.
Rupture: A forceful stretch actually tears the nerve, either partially or completely. This is more serious than a stretch injury and causes weakness in the shoulder, arm, or hand. Some muscles may become completely unusable. Ruptures often require surgical intervention to restore function.
Avulsion: The nerve root is ripped entirely away from the spinal cord. This is the most severe type and usually results from high-energy trauma like motorcycle or car accidents. Because reattaching a nerve root to the spinal cord is extremely difficult and often impossible, avulsions frequently lead to permanent weakness, paralysis, and loss of feeling. They also tend to cause severe, persistent pain.
Common Causes
In adults, high-speed trauma is the leading cause. Motorcycle and car accidents, contact sports, and falls that violently stretch the neck away from the shoulder can all damage the brachial plexus. The mechanism is usually a forceful widening of the angle between the head and shoulder, which stretches or tears the nerve roots.
In newborns, brachial plexus injuries occur during delivery, affecting roughly 0.05 to 0.26 percent of births. About half of these cases involve shoulder dystocia, where the baby’s shoulder gets caught behind the mother’s pelvic bone during delivery. Around a quarter involve other positioning complications. Notably, in more than half of cases of brachial plexus problems detected at birth, no shoulder dystocia or other delivery complication can be documented, suggesting the injury sometimes occurs from forces during otherwise normal labor.
Erb’s Palsy vs. Klumpke’s Palsy
The two most recognized patterns of brachial plexus injury have distinct physical appearances based on which nerve roots are damaged.
Erb’s palsy involves the upper nerve roots (C5 and C6) and is far more common, especially in newborns. It weakens the deltoid, rotator cuff muscles, biceps, and forearm rotators. The result is a characteristic “waiter’s tip” posture: the arm hangs at the side with the shoulder rotated inward, the elbow straight, and the forearm turned palm-down. The person can usually still move their fingers and wrist but struggles to lift the arm or bend the elbow.
Klumpke’s palsy affects the lower roots (C8 and T1) and targets the small muscles of the hand. It produces a “claw hand” appearance where the wrist extends upward (because the wrist extensors still work but the flexors don’t oppose them), the knuckle joints hyperextend, and the finger joints curl inward. Grip strength and fine motor control are severely compromised.
How It’s Diagnosed
Diagnosis starts with a physical exam. The pattern of weakness and sensory loss usually points clearly to which nerve roots are involved. Imaging and electrical testing help confirm the location and severity.
MRI is the standard imaging tool for visualizing nerve damage near the spinal cord, though it is better at showing some types of injury than others. Electromyography (EMG), which measures the electrical activity in muscles, plays a critical role in determining whether a nerve is completely disrupted or just temporarily stunned. However, timing matters: in the first week after injury, EMG cannot reliably rule out a complete nerve disruption unless it detects voluntary muscle activity. By three weeks, if a paralyzed muscle shows no signs of losing its nerve supply, EMG can confirm that the injury is a neuropraxia, the mildest type, which is expected to recover.
Treatment Options
Mild stretch injuries often recover without surgery. The nerve needs time and protection, and physical therapy keeps the joints mobile and muscles as active as possible while the nerve heals.
For more severe injuries, surgery becomes necessary. Two main surgical approaches exist. In a nerve graft, a surgeon takes a segment of nerve tissue, either from elsewhere in the patient’s body, from a processed donor nerve, or from an artificially grown graft, and uses it to bridge the gap in the damaged nerve. Nerve fibers then slowly regenerate across this bridge to reconnect with the muscles and skin on the other side.
In a nerve transfer, a surgeon reroutes a healthy, functioning nerve that the body can spare and connects it directly to the damaged nerve downstream from the injury. The healthy nerve’s fibers then grow through the damaged nerve’s pathway, gradually restoring signals to the muscles that lost function. Nerve transfers can be especially useful for avulsion injuries where the nerve root can’t be repaired at the spine.
Timing has a major impact on outcomes. A systematic review published in the Journal of Neurosurgery found that patients who underwent surgery within three months of injury achieved useful functional recovery nearly 90 percent of the time. That rate dropped steadily with longer delays, falling to just 35.7 percent when surgery was performed more than 12 months after injury.
Rehabilitation and Recovery
Regardless of whether surgery is involved, rehabilitation is a long process. Nerve fibers regenerate at roughly 1 millimeter per day in humans, which means regrowth from the neck to the hand can take many months or even over a year. During that time, the goals are to prevent joint stiffness, manage pain, and preserve as much function as possible.
Passive range-of-motion exercises start early, with a therapist or the patient gently moving affected joints through their full range to prevent them from locking up. Wrist and hand exercises continue even when the shoulder is immobilized after surgery. Splinting is commonly used: resting splints hold the hand and wrist in a natural position overnight, while dynamic splints with outriggers can assist finger extension during the day if the muscles haven’t recovered yet. For someone who has good hand function but is waiting for bicep recovery, a lockable elbow brace can position the arm for everyday tasks.
Once the earliest flickers of muscle activity return, electrical muscle stimulation can help strengthen the recovering muscles. General exercise is encouraged as healing allows, often starting with walking or pool-based exercise, where buoyancy supports the arm. For the persistent nerve pain that often accompanies these injuries, options include TENS (a device that delivers mild electrical pulses through the skin), acupuncture, and mirror therapy, a technique originally developed for phantom limb pain where watching the uninjured arm move in a mirror can help retrain the brain’s pain processing.
Despite the nerve’s capacity for repair, functional outcomes vary widely. Recovery depends on the severity and location of the injury, the distance nerve fibers must regrow, and how quickly treatment begins. Some people regain near-normal arm function. Others, particularly those with avulsion injuries or delayed treatment, may have lasting limitations in strength or sensation that require long-term adaptive strategies.