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

The brachial plexus—a complex network of nerves that sends signals from the spine to the shoulder, arm, and hand—can be severely affected by various traumatic and non-traumatic events. While these injuries are relatively rare, they can lead to significant loss of function and sensation in the upper extremities. Understanding the root causes is essential for prevention, timely diagnosis, and effective treatment.

Traumatic Injuries in Adults

One of the most common causes of brachial plexus injury in adults is high-impact trauma, particularly from motor vehicle accidents. Motorcycle crashes account for a large percentage of such cases, where riders are often thrown from their bikes upon impact. When the head and neck are forced away from the shoulder during a fall or collision, the brachial plexus nerves experience extreme stretching or traction.

This mechanism, known as a "traction injury," occurs when the distance between the neck and shoulder suddenly increases—similar to pulling a root out of the ground. In mild cases, this may result in nerve shock or temporary dysfunction (neuropraxia). However, in more severe incidents, the force can cause partial or complete avulsion of the nerve roots from the spinal cord, leading to permanent damage and loss of motor control.

Occupational and Mechanical Accidents

Workplace hazards also contribute significantly to brachial plexus injuries. Individuals operating heavy machinery, especially in industrial or manufacturing environments, are at risk if their arms or shoulders become caught in equipment, conveyor belts, or rotating mechanisms. These entanglement incidents generate powerful shearing or pulling forces that can stretch or tear the delicate nerve structures.

Additionally, direct compression from falling objects or prolonged pressure on the shoulder area—such as being pinned under debris during an accident—can crush or impair nerve function. Even seemingly minor incidents, if left untreated, may progress into chronic pain or paralysis due to nerve inflammation or scar tissue formation.

Obstetric Brachial Plexus Palsy in Newborns

While adult injuries are typically linked to external trauma, newborns can suffer brachial plexus damage during childbirth—a condition known as obstetrical brachial plexus palsy (OBPP). This usually occurs during a difficult delivery when the baby's shoulder becomes stuck behind the mother's pelvic bone, a complication referred to as shoulder dystocia.

In such cases, excessive lateral traction on the infant's head and neck while attempting to deliver the shoulders creates dangerous tension across the brachial plexus. The resulting strain can range from mild neurapraxia—which often resolves within weeks—to severe nerve ruptures or root avulsions requiring surgical intervention.

Risk Factors During Delivery

Certain factors increase the likelihood of OBPP, including fetal macrosomia (larger-than-average babies), maternal diabetes, prolonged labor, and the use of assistive devices like forceps or vacuum extractors. Although many infants recover with physical therapy and time, early assessment by pediatric neurologists is crucial to determine the extent of nerve involvement and initiate appropriate care.

Preventive strategies, such as proper prenatal monitoring and skilled management during delivery, play a vital role in reducing the incidence of birth-related brachial plexus injuries.

Conclusion

Brachial plexus injuries stem from a variety of causes, spanning high-speed accidents, workplace mishaps, and challenging births. Whether affecting adults or newborns, these nerve traumas demand prompt medical attention to maximize recovery potential. By recognizing the mechanisms behind these injuries and implementing safety measures—on the road, in the workplace, and during childbirth—we can reduce risks and improve long-term outcomes for those affected.