Causes of Brachial Plexus Injuries: Understanding Trauma, Birth Complications, and Risk Factors

Brachial plexus injuries can significantly impact arm function and overall quality of life. These injuries involve damage to the network of nerves that send signals from the spine to the shoulder, arm, and hand. While they can occur in various scenarios, most cases are linked to high-impact trauma or complications during childbirth. Understanding the underlying causes is essential for prevention, early diagnosis, and effective treatment.

Traumatic Injuries from Motor Vehicle Accidents

One of the leading causes of brachial plexus injury in adults is high-speed trauma, particularly from motorcycle or car accidents. When a person is thrown from a motorcycle or experiences a severe collision, the head and shoulder may be violently pulled in opposite directions. This sudden lateral traction stretches the brachial plexus beyond its normal limits, resulting in nerve damage.

In mild cases, this force may cause temporary nerve dysfunction known as neuropraxia or nerve shock, which can resolve over time. However, in more severe incidents, the nerves can be partially or completely torn from the spinal cord—a condition referred to as avulsion. This type of injury is sometimes described as resembling "pulling a carrot out of the ground," highlighting the extreme force involved.

Industrial and Mechanical Accidents

Workplace or industrial environments also pose risks for brachial plexus damage. Heavy objects falling onto the shoulder, or limbs getting caught in machinery, conveyor belts, or moving equipment, can generate enough force to stretch or compress the nerve network. These types of injuries are common in construction, manufacturing, and agricultural settings where safety protocols may not always be strictly followed.

Immediate medical evaluation is crucial in such cases, as delayed treatment can lead to permanent loss of motor function or sensation in the affected arm.

Obstetric Brachial Plexus Palsy in Newborns

Another significant cause of brachial plexus injury occurs during difficult childbirth. When a baby's shoulders become stuck behind the mother's pelvic bone—a condition known as shoulder dystocia—excessive pulling on the infant's head and neck may be required to deliver the baby safely. This maneuver can overextend the neck and shoulder, stretching or tearing the delicate nerves of the brachial plexus.

This form of injury, commonly called Erb's palsy, typically affects the upper nerves (C5-C6) and may result in weakness or paralysis of the arm. While many infants recover with physical therapy and time, some may require surgical intervention if nerve regeneration does not occur naturally.

Other Contributing Factors and Rare Causes

Besides trauma and birth complications, brachial plexus injuries can also stem from tumors, radiation therapy, or inflammatory conditions like Parsonage-Turner syndrome (neuralgic amyotrophy). Additionally, penetrating injuries such as knife wounds or gunshot injuries can directly damage the nerve network.

Early recognition of symptoms—such as numbness, lack of coordination, muscle weakness, or complete paralysis in the arm—is critical. Prompt imaging studies like MRI or electromyography (EMG) help determine the extent of nerve damage and guide appropriate treatment plans.

Prevention and Awareness

While not all brachial plexus injuries can be prevented, certain measures reduce risk. Wearing proper protective gear while riding motorcycles, following workplace safety regulations, and ensuring skilled obstetric care during delivery can significantly lower the likelihood of such injuries.

For individuals who have experienced trauma or notice neurological changes after an accident, seeking immediate medical attention improves outcomes and increases the chances of full recovery. Advances in microsurgical techniques and rehabilitation therapies continue to offer hope for improved function even in severe cases.