How to Diagnose Brachial Plexus Injuries in Infants and Adults

Understanding Brachial Plexus Injuries

Brachial plexus injuries are typically caused by trauma such as stretching, compression, or penetrating wounds. While these injuries can occur in adults due to accidents or sports-related incidents, they are most commonly associated with birth trauma in newborns. In particular, infants with high birth weight (macrosomia) are at increased risk during difficult deliveries, especially when excessive force is applied during shoulder dystocia. This physical stress can stretch or tear the network of nerves near the neck and shoulder, leading to brachial plexus damage.

Recognizing Early Signs in Newborns

One of the first noticeable signs of a brachial plexus injury in a newborn is limited or absent movement in one arm. Parents or medical professionals may observe that the affected limb hangs limply or shows significantly reduced motion compared to the other side. While some mild weakness may resolve on its own, persistent lack of mobility beyond the first few days warrants further evaluation. It's crucial for healthcare providers to monitor these symptoms closely, especially if there was a complicated delivery involving prolonged labor or assisted birth techniques like forceps or vacuum extraction.

The Role of Diagnostic Testing

When a brachial plexus injury is suspected, early diagnosis is key to determining the severity and planning appropriate treatment. The gold standard for confirming nerve damage is a diagnostic procedure known as needle electromyography (EMG). However, this test cannot be reliably performed immediately after birth. Nerve conduction changes take time to become detectable through electrophysiological studies—typically around 10 to 14 days post-injury.

Timing Matters: When to Perform Needle EMG

To ensure accurate results, needle EMG should be conducted no earlier than two weeks after birth. This delay allows sufficient time for Wallerian degeneration—a biological process where damaged nerve fibers break down and produce measurable electrical changes. Performing the test too soon may yield false-negative results, leading to missed or delayed diagnoses. After the two-week window, EMG can effectively identify which nerves are affected, assess the degree of injury, and help differentiate between neurapraxia (mild conduction block) and more severe forms like axonotmesis or neurotmesis.

Expanding the Diagnostic Scope

While brachial plexus injuries are the primary concern in upper limb dysfunction, similar diagnostic protocols apply to other peripheral nerve injuries. For example, peroneal nerve damage—often seen after lower limb trauma or knee surgery—also requires a follow-up EMG after at least 14 days to capture definitive neurological changes. Consistent timing across different nerve assessments ensures reliable data and supports evidence-based clinical decisions.

Toward Timely Intervention and Recovery

Early detection through properly timed EMG testing enables physicians to recommend targeted therapies, including physical therapy, occupational rehabilitation, or surgical consultation if needed. In infants, many cases of brachial plexus palsy improve within the first few months with conservative management. However, identifying non-responsive cases early allows for timely surgical intervention, which can significantly improve long-term outcomes.

In summary, diagnosing brachial plexus injuries involves careful observation of motor function in newborns, understanding risk factors related to childbirth, and utilizing precise electrodiagnostic tools at the right time. By following established guidelines—especially waiting until at least two weeks of age for needle EMG—clinicians can provide accurate diagnoses and set the stage for optimal recovery.