Brachial Plexus Injury: Understanding Symptoms, Types, and Functional Impacts
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 difficult childbirth—the result can be a brachial plexus injury. These injuries vary widely in severity and location, leading to distinct patterns of symptoms and functional limitations.
Types of Brachial Plexus Injuries and Their Clinical Presentations
Injuries to the brachial plexus are typically classified based on which nerve roots or trunks are affected. The specific pattern of damage determines the resulting motor and sensory deficits. Below is a breakdown of the most common types and their associated symptoms.
1. Upper Trunk (C5–C6) Injury – "Erb's Palsy"
Upper trunk injuries, often referred to as Erb's palsy, primarily affect the C5 and C6 nerve roots. This type commonly occurs during difficult deliveries or high-impact trauma. Patients typically experience significant weakness in shoulder abduction and elbow flexion. As a result, the affected arm may hang limply at the side, rotated inward, with the forearm extended and pronated—a posture known as "waiter's tip" deformity.
Muscles such as the deltoid, biceps, and brachialis are especially impacted, while grip strength and hand function usually remain intact. Early diagnosis and intervention, including physical therapy and sometimes surgical repair, can significantly improve outcomes.
2. Upper and Middle Trunk (C5–C7) Injury – Shoulder and Elbow Dysfunction
When both the upper and middle trunks are damaged, the impairment extends beyond the shoulder and biceps to include muscles controlled by the C7 root. This leads to more widespread dysfunction involving the elbow and wrist extensors.
Critical signs include complete loss of strength in the upper portion of the pectoralis major and latissimus dorsi muscles—both essential for shoulder stability and arm movement. Patients may struggle to lift or stabilize the arm, affecting daily activities like reaching, lifting, or pushing. Rehabilitation focuses on restoring range of motion and strengthening unaffected muscle groups to compensate for lost function.
3. Combined Upper-Middle and Partial Lower Trunk Injury – Involvement of Wrist and Finger Extension
In more extensive injuries affecting the upper and middle trunks along with partial damage to the lower trunk (C8–T1), patients begin to experience complications beyond the shoulder and elbow. The ability to extend the wrist and straighten the fingers becomes impaired due to compromised radial nerve function.
The upper segments of the pectoralis major and latissimus dorsi show no functional strength (graded 0/5), while the lower portions retain limited activity. This combination results in a mixed presentation: paralysis of proximal arm muscles alongside emerging hand weakness. Such cases often require multidisciplinary management, including nerve grafting, tendon transfers, and long-term occupational therapy.
4. Lower Trunk (C8–T1) Injury – Hand Function Impairment
Injuries isolated to the lower trunk primarily disrupt hand function. Also known as "Klumpke's paralysis," this type affects fine motor skills and grip strength. Patients may experience clawing of the hand, particularly in the ring and little fingers, due to intrinsic muscle atrophy.
Sensory loss is commonly reported along the medial forearm and hand. While shoulder and elbow movements remain largely preserved, the inability to perform precise hand tasks—such as writing, buttoning clothes, or holding small objects—can severely impact independence and quality of life.
5. Complete Brachial Plexus Injury – Total Upper Limb Paralysis
A complete brachial plexus injury involves all nerve roots (C5–T1) and results in total paralysis of the upper limb. All major muscle groups from the shoulder down to the hand lose voluntary control. Despite this, the trapezius muscle—innervated by the spinal accessory nerve (cranial nerve XI)—often remains functional, allowing patients to perform shrugging motions.
Due to the lack of muscular support, the shoulder joint frequently becomes unstable and may present with subluxation or even dislocation. Additionally, sensation throughout the arm is absent, and deep tendon reflexes (such as the biceps and triceps reflexes) are completely diminished or lost.
This severe form of injury typically requires aggressive treatment strategies, including microsurgical nerve reconstruction, muscle transfers, and extensive rehabilitation over months or years. Prognosis depends heavily on the timing of intervention and the extent of nerve damage.
Conclusion: Early Detection and Multimodal Treatment Are Key
Recognizing the specific pattern of weakness and sensory loss is crucial for diagnosing brachial plexus injuries accurately. From isolated upper trunk damage to complete plexus avulsion, each type presents unique challenges. Advances in imaging, electrodiagnostic testing, and reconstructive surgery have improved outcomes, but recovery often demands patience and comprehensive care.
If you or someone you know has experienced trauma followed by arm weakness or numbness, seeking prompt medical evaluation is essential. Early intervention can make a profound difference in regaining function and improving long-term prognosis.