Brachial Plexus Injury: Symptoms, Types, and Functional Impacts

Understanding Brachial Plexus Injuries

The brachial plexus is a complex network of nerves that sends signals from the spine to the shoulder, arm, and hand. When these nerves are stretched, compressed, or torn—often due to trauma such as car accidents, sports injuries, or childbirth—the result can be a brachial plexus injury. These injuries vary in severity and location, leading to a wide range of symptoms depending on which part of the nerve network is affected.

Different Types of Brachial Plexus Damage and Their Symptoms

Upper Trunk (Superior) Nerve Injury

When the upper trunk of the brachial plexus is damaged, patients typically experience weakness in shoulder abduction and elbow flexion. This means lifting the arm away from the body or bending the elbow becomes difficult. Common causes include falling on the shoulder or experiencing sudden downward force on the neck and shoulder region. The muscles primarily impacted include the deltoid and biceps, leading to reduced strength and mobility in daily activities.

Injury to the Upper and Middle Trunks

A more extensive injury involving both the upper and middle trunks results in significant impairment of shoulder and elbow function. In addition to weakened movement, patients may lose motor control in key muscle groups such as the latissimus dorsi and upper portion of the pectoralis major. Muscle strength in these areas may drop to grade 0, meaning no contraction or movement is possible. This type of injury often requires comprehensive rehabilitation and may necessitate surgical intervention for long-term recovery.

Combined Upper-Middle and Partial Lower Trunk Damage

This pattern of injury extends beyond the shoulder and elbow, affecting wrist extension and finger straightening abilities. Patients may struggle to lift their wrist or fully extend their fingers, resulting in what's sometimes called "wrist drop." Alongside this, the upper chest and back muscles remain severely weakened (grade 0), while lower portions show noticeable but partial strength loss. Such widespread dysfunction highlights the interconnected nature of the brachial plexus and emphasizes the need for early diagnosis and targeted therapy.

Lower Trunk (Inferior) Nerve Injury

Injuries isolated to the lower trunk primarily affect hand function. Individuals may experience numbness, tingling, or loss of fine motor skills in the hand and forearm. Tasks like gripping objects, typing, or buttoning a shirt become challenging. This type of damage is often associated with upward traction injuries, such as grabbing onto something during a fall. Sensory deficits are common, and without proper treatment, long-term disability in hand use can occur.

Complete Brachial Plexus Avulsion

The most severe form of brachial plexus injury involves total disruption of all nerve roots from C5 to T1. In these cases, complete paralysis of the upper limb occurs, with all voluntary muscle movements lost except for shoulder shrugging, which is controlled by the spinal accessory nerve (cranial nerve XI). The shoulder often appears droopy or partially dislocated due to lack of muscular support. Additionally, sensation throughout the arm is absent, and reflexes such as the biceps or triceps reflex are completely diminished or gone.

Why Early Diagnosis Matters

Recognizing the specific pattern of weakness and sensory loss is crucial for effective treatment planning. Imaging studies like MRI or nerve conduction tests help pinpoint the location and extent of nerve damage. Physical therapy, occupational therapy, and in some cases, nerve grafting or muscle transfers, play vital roles in restoring function. Prognosis depends heavily on the injury type and timing of intervention—early assessment significantly improves outcomes.

Conclusion

Brachial plexus injuries present a spectrum of neurological impairments, each requiring a tailored approach to rehabilitation. From limited shoulder movement to total arm paralysis, understanding the distinct symptom profiles allows healthcare providers to offer precise care. Whether recovering from trauma or managing congenital conditions, patients benefit greatly from multidisciplinary support focused on regaining independence and improving quality of life.