Brachial Plexus Birth Palsy

Definition: Brachial Plexus Birth Palsy (BPBP), also known as Obstetric Brachial Plexus Injury (OBPI), is a stretch injury to the brachial plexus occurring during delivery. It results from lateral flexion of the head away from the shoulder, causing traction on the plexus.

Epidemiology:

• Incidence: 1-2 per 1000 live births.
• Risk Factors: Shoulder dystocia, Macrosomia, Forceps/Vacuum delivery, Breech presentation.
• Recovery: Approximately 80-90% recover spontaneously, often fully or with minimal residual deficit.

Neuroanatomical Pattern:

• Upper Plexus (Erb's - C5, C6 +/- C7): Most common (80-90%). Best prognosis.
• Lower Plexus (Klumpke's - C8, T1): Rare in isolation (less than 5%). Associated with Horner's.
• Total Plexus (C5-T1): Flail arm. Worst prognosis.

Plexus Anatomy: The brachial plexus is formed by the ventral rami of C5-T1. It has 5 components (Roots, Trunks, Divisions, Cords, Branches).

• Upper Trunk: C5, C6.
• Middle Trunk: C7.
• Lower Trunk: C8, T1.
• Key Nerve Outputs: Musculocutaneous (Biceps), Axillary (Deltoid), Radial (Triceps/Wrist Extensors), Median (Forearm Flexors/Thenar), Ulnar (Intrinsics/Hypothenar).

Injury Mechanisms:

1. Stretch/Neurapraxia: Temporary conduction block. Full recovery expected.
2. Rupture: Nerve disrupted distal to DRG. Scar formation. May need grafting.
3. Avulsion: Root torn from spinal cord. No spontaneous recovery. Requires nerve transfer.

Pathophysiology of Late Shoulder Deformity: Muscle imbalance (Strong internal rotators vs Weak external rotators) leads to:

• Internal rotation contracture.
• Posterior subluxation of glenohumeral joint.
• Glenoid retroversion, posterior humeral head flattening.
• Ultimately, Glenohumeral Dysplasia (GHD).

Initial Exam (Newborn):

• Posture: Waiter's Tip? Flail? Claw?
• Passive ROM: Full in newborn (to exclude contracture or fracture).
• Reflexes: Moro (abducted arm doesn't follow), Grasp (if lower plexus involved).
• Horner's Syndrome: Ptosis, Miosis, Anhidrosis.
• Rule Out Fracture: Clavicle, Humerus (Pseudoparalysis). Order X-ray.

Serial Assessment:

• Active Movement: Use Active Movement Scale (AMS). 0-7 per muscle.
• Key Milestone: Biceps recovery. If antigravity biceps by 3-6 months, expect good recovery (Gilbert).
• Shoulder ROM: Monitor for internal rotation contracture (External Rotation deficit).
• Later: Mallet Classification for shoulder function.

Mallet Classification (Shoulder Function): Grades shoulder function (Abduction, External Rotation, Hand to Mouth, etc.).

• Grade I: Flail shoulder.
• Grade V: Normal.
• Grade II-IV: Intermediate.

Imaging:

1. X-ray (Clavicle, Humerus): Initial. Rule out fracture.
2. MRI Brachial Plexus: If no recovery by 3 months. Look for pseudomeningoceles (root avulsion), neuroma.
3. Ultrasound Shoulder: Assess glenohumeral joint if internal rotation contracture. Look for posterior subluxation, glenoid retroversion.
4. CT Shoulder (3D): For surgical planning in older children with GHD.

Electrodiagnostics:

• EMG/NCS: Can differentiate neurapraxia from axonotmesis/avulsion. Often used to supplement clinical exam.
• Timing: 3-4 weeks after injury (for fibrillation potentials).

The flaccid or under-moving newborn arm has several mimics. The single most important step is to exclude a painful pseudoparalysis (fracture, infection) before attributing weakness to plexopathy.

Glenohumeral Dysplasia (GHD): The major late complication. Characterized by:

• Glenoid retroversion.
• Posterior subluxation of humeral head.
• Flattening of humeral head.
• Eventual osteoarthritis.

• Nerve Surgery: Sling/Shoulder Immobilizer. Gentle ROM at 4-6 weeks. Expect recovery over 12-18 months.
• Tendon Transfer/Release: External Rotation Immobilization (Spica or Brace) for 6 weeks. Intensive physio after.
• Osteotomy: Sling. ROM as tolerated. Bone healing in 6-8 weeks.

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• Erb's (Type I): Greater than 90% recover good function (Mallet IV-V).
• Total Palsy (Type III/IV): Poor prognosis. Permanent deficits common.
• Nerve Surgery: Improves function significantly but rarely restores normal.
• Long-term: Shoulder problems (GHD, OA) are the main late issues.

Global Epidemiology:

• Incidence approximately 1-2 per 1000 live births, falling in high-resource settings. A Swedish national registry recorded a decline from 3.1 to 1.0 per 1000 cephalic vaginal births between 1997 and 2019 despite rising recognition of shoulder dystocia (PMID 36345990).
• Risk factors: shoulder dystocia, fetal macrosomia, maternal gestational diabetes, instrumental (forceps/vacuum) delivery, prolonged second stage, and breech delivery. Notably, a proportion of cases occur without documented dystocia (including caesarean births), implicating in-utero maladaptation.
• Upper-trunk (Erb's) pattern accounts for roughly 80-90% of cases and carries the best prognosis.

Side-by-Side Guidance:

Service Organisation & Resource Variation:

• High-resource settings: dedicated multidisciplinary plexus clinics (paediatric hand/peripheral-nerve surgery, physiotherapy, occupational therapy), early MRI and microsurgical capability, and structured glenohumeral surveillance.
• Limited-resource settings: emphasis on prevention (dystocia training, gestational diabetes screening), parent-delivered range-of-motion therapy, and clear referral pathways; advanced microsurgery and secondary reconstruction may be regionally centralised or unavailable, making timely triage critical.
• Universal principles: exclude a fracture, protect passive range of motion, document serial active movement, refer early if recovery stalls, and monitor lifelong for shoulder dysplasia regardless of setting.