Residency · Residency · Neurosurgery
Brachial Plexus Injury: Evaluation and Reconstruction
Introduction
The brachial plexus is a complex neural network originating from the C5 through T1 nerve roots that innervates the entire upper extremity. Injuries range from mild traction neuropraxia to devastating root avulsions. Obstetric brachial plexus injury affects 1 to 3 per 1,000 live births, while adult injuries predominantly result from high-energy trauma. Neurosurgical evaluation and reconstruction require precise anatomic knowledge, electrodiagnostic expertise, and familiarity with nerve transfer and grafting techniques.
Anatomy
Components of the Brachial Plexus
The brachial plexus is organized into five sequential components. The roots consist of the C5, C6, C7, C8, and T1 ventral rami. These roots form three trunks: the upper trunk from C5 and C6, the middle trunk from C7, and the lower trunk from C8 and T1. Each trunk splits into anterior and posterior divisions. The divisions then reform into three cords: the lateral cord from the anterior divisions of the upper and middle trunks, the posterior cord from all posterior divisions, and the medial cord from the anterior division of the lower trunk. The terminal branches include the musculocutaneous, axillary, radial, median, and ulnar nerves.
Key Anatomic Relationships
The plexus courses between the anterior and middle scalene muscles. The long thoracic nerve arising from C5 through C7 innervates the serratus anterior, and its injury causes scapular winging. The dorsal scapular nerve from C5 innervates the rhomboids. The supraclavicular plexus encompasses the roots and trunks above the clavicle, while the infraclavicular plexus includes the divisions, cords, and branches below the clavicle.
Classification of Injury
By Level
Upper plexus injury involving C5 and C6, known as Erb-Duchenne palsy, produces loss of shoulder abduction and external rotation, elbow flexion, and forearm supination, resulting in the characteristic waiter's tip posture. Extended upper plexus injury involving C5 through C7 adds loss of wrist and finger extension. Lower plexus injury involving C8 and T1, known as Klumpke palsy, causes loss of intrinsic hand function and wrist and finger flexion. Pan-plexus injury involving C5 through T1 results in complete upper extremity paralysis with a flail arm.
| Injury Pattern | Roots | Eponym | Motor Loss | Posture/Presentation |
|---|---|---|---|---|
| Upper plexus | C5-C6 | Erb-Duchenne | Shoulder abduction/ER, elbow flexion, supination | Waiter's tip |
| Extended upper | C5-C7 | — | Above + wrist/finger extension | Waiter's tip + wrist drop |
| Lower plexus | C8-T1 | Klumpke | Hand intrinsics, wrist/finger flexion | Claw hand; ± Horner syndrome |
| Pan-plexus | C5-T1 | — | Complete upper extremity paralysis | Flail arm |
By Severity
Preganglionic injuries, or root avulsions, involve the nerve root being torn from the spinal cord and cannot be repaired directly. Signs include Horner syndrome with T1 avulsion, scapular winging with C5 through C7 injury, rhomboid weakness with C5 involvement, and diaphragm paralysis with C3 through C5 involvement. The histamine test shows an absent flare response in preganglionic lesions. Crucially, SNAPs are preserved despite clinical sensory loss because the dorsal root ganglion remains intact. Postganglionic injuries, including ruptures and stretches, occur distal to the dorsal root ganglion and are amenable to direct repair or grafting.
Evaluation
Clinical Assessment
A detailed motor examination of every muscle group innervated by the brachial plexus is essential, along with sensory examination of dermatomes C5 through T1. Horner syndrome, consisting of miosis, ptosis, and anhidrosis, indicates T1 root avulsion. The Tinel sign is assessed along the course of the plexus to localize the injury. Associated injuries must be documented, including vascular injuries to the subclavian or axillary artery and skeletal injuries such as clavicle, scapula, or humerus fractures.
Imaging
MRI neurography visualizes root avulsions indicated by pseudomeningoceles, nerve discontinuity, and surrounding soft tissue abnormalities. CT myelography remains the gold standard for confirming root avulsions, demonstrating absence of rootlets and pseudomeningoceles. Chest X-ray showing an elevated hemidiaphragm suggests phrenic nerve involvement from C3 through C5. Ultrasound has an emerging role in visualizing nerve continuity and neuromas.
Electrodiagnostic Studies
The initial electrodiagnostic study is performed at 3 to 4 weeks with repeat studies at 3 and 6 months. SNAPs preserved in the presence of clinical sensory loss are pathognomonic for preganglionic root avulsion injury. EMG of paraspinal muscles showing denervation supports root-level injury. Serial studies track reinnervation, with nascent MUAPs indicating recovery. Absence of recovery at 3 to 6 months is an indication for surgical exploration.
Surgical Reconstruction
Timing
Early exploration at 3 to 6 months for closed injuries is pursued if no clinical or electrodiagnostic recovery is observed. Immediate exploration is warranted for open or sharp injuries, vascular injuries requiring surgical repair, or gunshot wounds with progressive deficit. Delayed reconstruction beyond 12 months has worse outcomes due to irreversible motor endplate degeneration.
Surgical Techniques
Neurolysis involves external or internal release of scar tissue around an intact nerve. Direct nerve repair with end-to-end coaptation is performed when nerve ends can be approximated without tension, using epineurial or grouped fascicular repair. Nerve grafting with sural nerve autograft is the gold standard for bridging gaps, with cables of graft fascicles spanning the defect.
Nerve transfer involves coapting a functioning but expendable donor nerve to the distal stump of a more important paralyzed nerve. The Oberlin transfer uses an ulnar nerve fascicle transferred to the musculocutaneous nerve biceps branch to restore elbow flexion. Spinal accessory to suprascapular nerve transfer restores shoulder abduction and external rotation. Intercostal nerve transfers to the musculocutaneous nerve provide elbow flexion especially in root avulsions. Medial pectoral to axillary nerve transfer reinnervates the deltoid.
Free functioning muscle transfer is reserved for late presentations beyond 12 months when motor endplates have degenerated, with the gracilis free flap being the most commonly used donor.
Obstetric Brachial Plexus Injury
Obstetric brachial plexus injury occurs in 1 to 3 per 1,000 live births, with risk factors including shoulder dystocia, macrosomia, and instrumental delivery. The most common pattern is upper plexus injury or Erb palsy involving C5 and C6. Natural recovery occurs in 70 to 90 percent of cases within 3 to 6 months. Failure to achieve antigravity elbow flexion by 3 months, assessed by the cookie test, is an indication for surgical exploration. Surgical options include nerve grafting and nerve transfers, with outcomes best when performed by 6 to 9 months of age. Secondary procedures such as tendon transfers and osteotomies address residual shoulder internal rotation contracture.
Clinical Pearls
Preserved SNAPs in the presence of clinical sensory loss are pathognomonic for preganglionic root avulsion and indicate that direct nerve repair is not possible. Horner syndrome in a brachial plexus injury indicates T1 root avulsion and is associated with a poor prognosis for hand function. The Oberlin transfer, using an ulnar fascicle to the biceps motor branch, is one of the most reliable nerve transfers for restoring elbow flexion in upper plexus injuries. Obstetric brachial plexus injury with failure of elbow flexion recovery by 3 months warrants surgical consultation. Surgical timing is critical, as nerve transfers and grafting should be performed within 6 months for optimal motor recovery.
References
- Mackinnon SE. Nerve Surgery. Thieme; 2015.
- Narakas AO. The treatment of brachial plexus injuries. Int Orthop. 1985;9(1):29-36.
- Oberlin C, Beal D, Leechavengvongs S, et al. Nerve transfer to biceps muscle using a part of ulnar nerve for C5-C6 avulsion. J Hand Surg Am. 1994;19(2):232-237.
- Waters PM. Update on management of pediatric brachial plexus palsy. J Pediatr Orthop. 2005;25(1):116-126.