# Brachial Plexus Birth Injury

## Introduction

**Brachial plexus birth injury (BPBI)** refers to stretch or traction injuries to the brachial plexus sustained during delivery. The incidence ranges from 0.4 to 5.1 per 1,000 live births. Early recognition and coordinated multidisciplinary management are essential for optimizing functional outcomes in affected infants.

## Anatomy and Classification

### Brachial Plexus Anatomy
The brachial plexus arises from **C5-T1** nerve roots. Organized into roots, trunks, divisions, cords, and terminal branches. Upper plexus (C5-C6) controls shoulder and elbow function. Lower plexus (C8-T1) controls hand and wrist function.

### Injury Classification
**Erb-Duchenne palsy (C5-C6)**: Most common type (approximately 75% of cases); affects shoulder abduction, external rotation, elbow flexion, and forearm supination. **Extended Erb palsy (C5-C7)**: Includes wrist and finger extension weakness. **Klumpke palsy (C8-T1)**: Rare; affects hand intrinsics and finger flexors. **Total plexus palsy (C5-T1)**: Flail arm with possible Horner syndrome.

| Type | Roots | Frequency | Motor Deficit | Key Features |
|------|-------|-----------|--------------|--------------|
| Erb-Duchenne | C5-C6 | ~75% | Shoulder abduction/ER, elbow flexion, supination | "Waiter's tip" posture |
| Extended Erb | C5-C7 | ~20% | Above + wrist/finger extension | More extensive UE weakness |
| Klumpke | C8-T1 | Rare | Hand intrinsics, finger flexors | May have Horner syndrome |
| Total plexus | C5-T1 | ~5% | Flail arm | Horner syndrome if T1 avulsed |

### Pathology Spectrum
**Neurapraxia**: Stretch without structural damage; best prognosis. **Axonotmesis**: Axonal disruption with intact endoneurium. **Neurotmesis**: Complete nerve disruption. **Avulsion**: Root torn from spinal cord; worst prognosis.

## Risk Factors

**Shoulder dystocia** (most significant). Macrosomia (birth weight >4,000 g). Gestational diabetes. Prolonged labor or instrumental delivery. Breech presentation. Prior BPBI in sibling.

## Clinical Evaluation

### Physical Examination
**Active Movement Scale (AMS)**: Gold standard for motor assessment in infants (0-7 scale). Asymmetric Moro reflex. Assess for associated injuries: clavicle fracture, humeral fracture, torticollis. Evaluate for **Horner syndrome** (ptosis, miosis, anhidrosis) indicating T1 involvement. Serial examinations to document recovery trajectory.

### Imaging and Diagnostics
**MRI of brachial plexus**: Identifies pseudomeningoceles suggesting root avulsion. **CT myelography**: Alternative for avulsion detection. **Electrodiagnostic studies**: Performed at 3-4 weeks; assess denervation and reinnervation. Ultrasound for associated musculoskeletal injuries.

![Brachial plexus anatomy showing roots, trunks, divisions, cords, and terminal branches](images/brachial-plexus-anatomy.jpg) ![Active Movement Scale scoring chart for infant motor assessment](images/active-movement-scale.jpg)

## Management

### Conservative Management
**Early gentle range of motion** exercises beginning at 7-10 days of life. Parent education on positioning and handling. Splinting to prevent contractures (especially elbow flexion, forearm supination). Occupational therapy for sensory stimulation and developmental activities.

### Surgical Indications
No biceps function by **3-6 months** of age (cookie test). Total plexus palsy with Horner syndrome. Failure to progress on serial AMS assessments. **Nerve surgery options**: Neurolysis, nerve grafting, nerve transfers (e.g., Oberlin transfer).

### Secondary Procedures
**Muscle-tendon transfers**: Latissimus dorsi and teres major transfer for external rotation. **Shoulder reduction and osteotomy** for posterior glenohumeral dysplasia. Botulinum toxin injections for co-contraction management. Tendon lengthening for contractures.

### Rehabilitation Across Development
Infancy: Passive and active-assisted ROM, sensory play. Toddler: Bimanual activities, constraint-induced movement therapy (CIMT). School age: Sport modification, adaptive equipment, strengthening. Adolescence: Vocational planning, psychosocial support.

![Posterior glenohumeral dysplasia on MRI in chronic brachial plexus birth injury](images/glenohumeral-dysplasia-bpbi.jpg)

## Complications

**Posterior shoulder subluxation/dislocation** due to internal rotation contracture. Glenohumeral dysplasia from muscle imbalance. Limb length discrepancy. Learned non-use of affected extremity. Psychosocial impact on child and family.

## Prognosis

**70-80%** of neonates with BPBI recover spontaneously by 3-6 months. Biceps recovery by 3 months is a favorable prognostic sign. Total plexus injuries and avulsions carry the worst prognosis. Long-term follow-up through skeletal maturity is recommended.

## Key Clinical Pearls

1. The **Active Movement Scale** is the preferred tool for serial motor assessment in infants with BPBI, as manual muscle testing is unreliable in this population. 2. Absence of biceps function by 3-6 months is the primary indication for microsurgical exploration and nerve reconstruction. 3. **Posterior glenohumeral dysplasia** is the most common skeletal deformity and requires ongoing surveillance with imaging. 4. A multidisciplinary team including physiatry, hand surgery, orthopedics, and therapy is essential for optimal long-term outcomes.

## References

1. Abzug JM, Kozin SH. Evaluation and management of brachial plexus birth palsy. *Orthopedic Clinics of North America*. 2014;45(2):225-232.
2. Hale HB, Bae DS, Waters PM. Current concepts in the management of brachial plexus birth palsy. *Journal of Hand Surgery*. 2010;35(2):322-331.
3. Pondaag W, Malessy MJ, van Dijk JG, Thomeer RT. Natural history of obstetric brachial plexus palsy: a systematic review. *Developmental Medicine & Child Neurology*. 2004;46(2):138-144.
4. Coroneos CJ, Voineskos SH, Christakis MK, et al. Obstetrical brachial plexus injury: a systematic review of primary and secondary reconstruction. *Plastic and Reconstructive Surgery*. 2017;139(3):697e-720e.